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RR125 is similar to bronzehull Type 2 weedy rice while RR126 is a strawhull type that is mostly awnless. In phylogenetic analysis, RR125 was grouped with Type 2 weedy rice and RR126 was grouped with Type 5 weedy rice . STRUCTURE indicated membership of RR125 to the genetic cluster composed primarily of Type 2 weedy rice with a small amount of admixture from the cluster composed primarily of Type 1 weedy rice . RR126 assigned with 100% membership to the genetic cluster composed of Type 5 weedy rice and japonica rice varieties . Our evaluation of seed shattering and seed dormancy at 35–40 days after flowering indicated that RR125 has low shattering and no seed dormancy , similar to cultivated rice . RR126 is also non-shattering, but has high seed dormancy . These results em‐ phasize the need for a consensus definition of weedy rice, as not all red‐pericarped rices are weedy. However, the clustering of both RR125 and RR126 with weedy rice biotypes does indicate possible genetic contributions from red‐pericarped varieties into weedy populations. This potentially problematic relationship calls for careful management of rice seed and certification to avoid the contamination of white‐pericarped cultivated rice acreage with red‐pericarped specialty rice or its weedy relatives. The genetic clustering of individuals by biotype observed in phylogenetic, STRUCTURE, curing cannabis and PCA analyses indicate that phenotypic similarity is a better indicator of relatedness than geographic proximity for California weedy rice.

The four major biotypes all contained samples from multiple different counties, and the only location where all individuals belong to the same biotype is Colusa County . The spread of biotypes across a large geographic area is likely the result of seed movement, as pollen of both cultivated and wild rice travels only up to 100 m from source plants . The most likely mode of weedy rice seed movement over long distance is dispersal by humans, either through contaminated seed stocks or equipment within California or through additional introductions of weedy rice from other rice‐growing regions. This highlights the need for growing weed‐free certified seed in California and encouraging growers to prevent the spread of weedy rice on contaminated equipment. Recent regulations regarding the importation of used equipment and the requirement for only planting certified seed or seed from a third‐party quality assurance program should aid in these efforts . Overall, the phylogenetic, population structure, and principal component analyses above allow some insights into the ancestry of California weedy rice and into the prevalence of evolutionary histories of de-domestication. Type 1 weedy rice is likely evolutionarily derived from aus rice or possibly a wild rice species, as is the black‐ hull awned rice from the southern United States . These two American weedy rice biotypes may have a single origin from Asian rice or separate origins followed by hybridization with each other. However, they are both genetically and phenotypically distinct, as Type 1 rice is neither blackhulled or awned . Because the specific origins and any subsequent hybridization are unclear, it cannot be determined whether this biotype is derived from endoferal de‐domestication directly from the crop cultivars or exoferal de‐domestication through hybridization of cultivars and/or weedy populations.

Type 2 weedy rice is most closely related to strawhull weedy rice from the southern United States, and these two groups likely evolved by exoferal de‐domestication from indica rice. Alternatively, these two groups were also placed with wild rice species in several analyses and could have some ancestry from undomesticated rice. Regardless, it is unclear whether Type 2 and southern strawhull weedy rice have a single or separate origins. Type 3 weedy rice of California is highly differentiated from other rice types and has ambiguous evolutionary origins. Based on its closest relationship in the phylogenetic analysis, it appears to have evolved from wild rice and may have retained wild traits such as pubescence of leaves, presence of long awn, high seed dor‐ mancy, and shattering, consistent with the results of Londo and Schaal using a single California weedy rice genotype . In another study of Type 3 weedy rice by Kanapeckas et al. , California strawhull weedy rice had the lowest mean population divergence from O. rufipogon from South East Asia, but was interpreted as having diverged from California cultivated rice based on coalescent modeling analysis. More study of this weedy rice bio‐ type may be needed to fully understand its evolutionary origins. Type 4 weedy rice is most likely descended from Type 3 weedy rice. Type 5 weedy rice is endoferally derived from japonica rice, and it is not clear whether the direct ancestor is tropical japonica rice or temperate japonica rice grown inside or outside of California. For all California weedy rice biotypes, the presence of the causative Rc allele for red pericarp associated with wild rice or landrace rice never selected for white pericarp means that genetic contributions of endoferal ancestry from landrace rice or exoferal ancestry from wild rice cannot be ruled out. In conclusion, the five major California weedy rice biotypes are not all closely related to each other and have diverse parentage from several major lineages of cultivated rice and wild rice, as well as relationships with weedy rice from the southern United States.

Most bio‐ types are likely derived from independent origins outside of California, although hybridization between biotypes or with local cultivars may contribute to the evolution of weedy rice populations. Future study of California weedy rice with sequence data may help elucidate the evolutionary relationships of weedy rice types with currently ambiguous origins. The recent rediscovery and rapid spread of multiple weedy rice biotypes with evolutionary origins outside of California highlights the need for management of current weedy populations and measures to prevent further introductions of weedy rice into California.Rice is produced on about 500,000 acres in the Sacramento Valley annually, making it the region’s major crop. Rice is a cereal crop that has been grown in California since the early 1900s. It is grown in flooded soils, so it is ideally suited to the poorly drained soils common to much of the Sacramento Valley. Most rice growers till both in the fall to incorporate rice straw and in the spring to prepare the seedbed. Typical spring tillage involves six to eight tractor passes that include chisel plowing, disking and planing before applying fertilizer, and rolling the field in preparation for planting. No-till rice systems are not likely to be successful in California because harvesting equipment can leave deep tracks in the field that results in poor rice establishment and weed problems. Fall tillage is necessary to level the field and incorporate rice straw, but minimum-till rice systems with no spring tillage may be an option. Minimum-till systems are not new to rice and are being evaluated in the southern United States and Asia . In these areas, weed dryer rice is grown in rotation with other crops such as soybean and wheat, respectively. In contrast, most California rice systems do not involve crop rotations due to the heavy soils on which they are grown. Nevertheless, there is increasing interest in growing rice in California with no spring tillage due to the potential for reduced fuel costs, earlier planting , better control of herbicide-resistant weeds, and potential air-quality improvements due to reduced dust. Herbicide-resistant weeds are one of the main problems threatening the long-term sustainability of California’s rice-based systems. In fact, California rice has seven herbicide-resistant weed species, more than any other crop or geographic area in the United States . Herbicide resistance has evolved in rice weed populations due to repeated use of the same herbicide, herbicides having the same mode of action, or herbicides detoxified by a common mechanism in plants and weeds. Minimum tillage with a stale seedbed offers new opportunities to control herbicide-resistant weeds in California rice fields.

The approach entails preparing a stale seedbed before planting by flushing or flooding the field with water to induce weed-seed germination, and then killing the weeds, usually with glyphosate. The choice between flushing or flooding depends on whether or not the field is infested with weeds that require water saturation to germinate. The soil is then left untilled to ensure that buried weed seeds are not brought to the surface to germinate. This combination of a stale seedbed and no spring tillage can currently control all types of herbicide-resistant weeds in California rice systems, because they are not resistant to glyphosate.An experiment was initiated in 2004 at the California Rice Experiment Station near Biggs in Butte County, to evaluate crop establishment methods and their effects on rice yield, weed and pest populations, and nitrogen cycling. The experiment was set up as a randomized complete block design with four replications on 0.5-acre plots. In this paper we discuss two treatments: water-seeded conventional till and water-seeded minimum till with a stale seedbed. Water-seeding refers to broadcasting rice seed into a flooded field, a practice used by more than 90% of California rice growers. In both treatments, the plots were tilled in the fall to incorporate rice straw and then flooded to encourage straw decomposition. The conventional-till treatment replicated the practice of most California rice growers, and entailed spring tillage , flooding and planting. The minimum-till treatment had no spring tillage but the plots were flushed with water to prepare a stale seedbed prior to planting. Both the conventional- and minimumtill plots were flooded and planted on the same day. The plots remained flooded until a few weeks before harvest. Weed control. In the minimum-till treatment a stale seedbed was prepared, which entailed flushing the plots with water in April and then draining. After the weeds germinated, glyphosate was applied at a rate of 1.2 pounds acid equivalent per acre. Other than this, weeds in both tillage treatments were managed similarly during the growing season with the objective of obtaining full control. This was accomplished using propanil and penoxsulam applied at the four- to five-leaf stage of rice. This mixture of broad-spectrum herbicides with different modes of action is the currently recommended practice for managing herbicide-resistant weeds. A 3,000-square-foot portion of each plot was left untreated to monitor weed recruitment and evaluate the effectiveness of the stale seedbed. In the minimum-till treatment, this area received glyphosate prior to planting but not the other herbicides used in the the leaf-eating adults. Adult weevil feeding was monitored from the three-to-five rice leaf stage. Larvae were counted twice in 10 soil samples in all plots in July. Fertilizer management. Fertilizer management varied between the two study treatments due to differences in water management and tillage. Phosphorus and potassium fertilizer were applied on all plots prior to permanent flooding. In the conventional tillage plots the phosphorus and potassium were tilled into the soil with the tillage operations, but in the minimumtill system it remained on the surface. Nitrogen fertilizer was applied at a rate of 150 pounds per acre, within the recommended range for rice . In the conventional till system, the field remained permanently flooded and anaerobic, and all of the nitrogen was applied in a single dose incorporated 3 to 4 inches below the soil surface prior to planting. In the minimum-till system, since the soil was left undisturbed following the stale seedbed treatment, nitrogen fertilizer was applied on the soil surface instead of below it. Two-thirds of the nitrogen was broadcast on the surface just before flooding for planting, and the remaining third was broadcast between 40 and 50 days after planting. Nitrogen fertility trial. To determine the most efficient nitrogen management practices for each tillage system, a nitrogen fertility trial was conducted in 2004 and 2006. This trial included five 400-square-foot subplots within each plot to which no nitrogen fertilizer had previously been applied. The location of these subplots within the main plots changed each year to avoid the compounding effects of the nitrogen fertility treatments. Nitrogen fertilizer rates ranged from 0 to 200 pounds per acre in the subplots . In the conventional-till treatment, nitrogen was always applied as a single dose and incorporated below the soil surface before flooding for planting. In the minimum-till treatment, nitrogen was applied either as a single dose or split between two doses. Data analysis. All data were analyzed using Statistical Analysis System software. Main plot yields, weed data and water weevil data were analyzed using a randomized complete block design. The nitrogen fertility trial was analyzed using a split-plot design.

Primarily, we desire to underscore the need for thoughtful and strategic restoration that is paired with invasive species control. In a cautionary example of the importance of such a pairing, managers in southwestern riparian ecosystems achieved success in controlling the invasive Salt Cedar , only to discover that without combining control efforts with native vegetation restoration, the endangered Southwestern Willow Fly Catcher struggled to locate nesting habitat . There are many impediments to effective adaptive management in the Delta, including a general trend of managers’ failure to evaluate and synthesize management results . However, the present case study is an example of state and federal agency employees collaborating with academic researchers to address this common pitfall by evaluating the results of management operations and incorporating the evidence into decision-making about future management activities. More broadly, we hope this case study is a useful example for managers around the world who manage invasive species in the context of aquatic food webs. Modern ecological restoration projects generally focus on short term interventions due to limited funding, finite resources, dry racking and short policy or grant cycles. We define short-term intervention efforts as the “implementation phase” recognized by the Society for Ecological Restoration, which includes the initial 1–5 years of restoration .

This implementation phase involves substantial money, labor, equipment, and other resources to alter the abiotic environment, remove exotic species, and introduce native species. The implementation phase initiates ecosystem recovery by targeting and manipulating key determinants of successional pathways . After short-term restoration efforts cease, the restored ecosystems become subject to ambient drivers of succession, such as the natural recruitment of plants via existing populations and uncontrolled environmental conditions that favor some species over others . For desired native populations to persist past the initial implementation phase, natural recruitment and environmental conditions must favor these native species. Landscape context has long been recognized as an important factor influencing the trajectory of a restoration site . Landscape heterogeneity, such as grasslands scattered with trees, can contain species-rich microhabitats that increase overall species diversity . Land use history also affects species diversity, as undisturbed landscapes can harbor species-rich seed banks. Seed availability and dispersal also affect species diversity in restoration sites, and there is a tendency for restoration sites to become dominated by weedy species that are already present at the site . For natural recruitment into a restored site to be dominated by desirable species, the most abundant populations in the matrix surrounding the restoration site should be native species . Initial restoration plantings often establish small populations of desirable species that frequently exist as patches within a fragmented landscape otherwise dominated by undesirable exotic species and isolated from other native populations .

In such settings, after the implementation phase ends, isolated restored sites may become reinvaded quickly by undesirable species from the surrounding landscape. Even if there are native individuals present, environmental conditions may prevent population growth and even result in local extirpation . For example, restored wetlands that established an average of 28 native species within the implementation phase subsequently experienced a decline in richness to 12 native species 6 years later . Reinvasion of restored ecosystems by exotic species is a common challenge faced by restoration practitioners, and it is well known that exotic species are particularly adept at colonizing open niche spaces following disturbances and under shifting climatic conditions . One-time exotic species removal efforts can also lead to a secondary invasion, wherein another invasive species establishes after the removal of the original invasive species . Pearson et al. found that secondary invasion of exotic species occurred in all 60 of the weed management projects they surveyed in a global meta-analysis. They found a strong inverse relationship between secondary invader abundance and original invader abundance, suggesting that secondary invaders took advantage of reduced competition and more resources after the original invaders were eradicated. Vernal pool assemblages in California, U.S.A., are especially susceptible to reinvasion by exotic plants after initial restoration, particularly by annual grasses from Europe . In California’s Mediterranean climate, vernal pools form atop an impermeable subsurface soil layer during the cool, wet winters and then dry out during the warm, dry summers . Endemic plant species flourish in this unique environment with adaptations that allow them to survive prolonged flooding, while also growing and reproducing quickly before pools completely desiccate during the summer . Specialist species that have adapted to withstand this hydrologic regime can take advantage of the lower amount of competition in these harsh environments .

Some native plant species, such as Lasthenia fremontii , are only found in the deepest, most inundated zone of the pool and cannot withstand drier conditions, whereas other species, such as Limnanthes alba , are adapted to slightly drier conditions along the shallower edge zones of the pool and cannot withstand extreme flooding events . The pool landscape can be heterogeneous within the space of a few meters, which has direct implications for native species growth and persistence and thus restoration and management. In addition, pools typically exist within a landscape matrix that is dominated by invasive exotic plant species, resulting in edge effects wherein the pool margins are exposed to the invasion front of surrounding exotic species . Vernal pool restoration projects have had varying levels of success, particularly in southern California . This may be due to variable site characteristics and competitive pressures from exotic plant species in some zones of the pool or some parts of the pool complex . Restoration actions often consist of topographic excavation of deeper pool basins, resulting in prolonged flooding of the central zone of the pool, followed by the addition of native plants. Creating wet abiotic conditions allows any added native seed to grow and reproduce without competition from invasive exotic species that cannot withstand inundation. Yet, cannabis curing as elevation increases up to the pool’s edge, conditions become drier, and the community is more susceptible to invasion by generalist European grasses that can opportunistically invade drier open niche space . Gerhardt and Collinge showed that, even when native species were abundant, a longer inundation period was needed to preclude subsequent exotic invasion. They manipulated the inundation period in a greenhouse experiment and found that, although the growth and reproduction of some exotic species were reduced when grown with native species, longer inundation significantly decreased the survival of exotic species. A field study by Faist and Beals similarly found that pools with higher invasive species cover also had shorter inundation periods. Drier years can cause an increase in exotic forbs in pool basins, likely due to the lack of abiotic resistance normally afforded by flooding . In addition to the abiotic conditions that need to be established in the pool center to reduce its invasibility, biotic manipulation of the pool edges may need to be a continual effort to prevent exotic reinvasion . Marty reported that an increase in exotic species cover coincided with the discontinuation of a vernal pool site’s weed management program, which had included grazing. Marty found that reintroducing grazing allowed pool plant communities to recover significantly higher native cover than ungrazed pools, with the greatest increase in native plant cover found around the pool edges. These edge effects, or conditions at the edges of sites that alter abiotic conditions, species composition, and ecological processes, can often have detrimental ecological consequences . For example, hotter, drier, and more variable conditions along exposed forest edges can result in higher tree mortality rates, and exotic propagule pressure and anthropogenic disturbance can correlate with higher exotic plant species and lower native plant species on the edges of preserved grasslands . In vernal pools, pools with more edge area exposed to surrounding unrestored grassland may also be more susceptible to similar edge effects, including invasion. Habitat fragmentation studies have shown that fragments with higher perimeter-to-area ratios exhibit higher exotic cover .

Restoration efforts in these drier zones often include weeding out invading exotics, which is generally not needed in the central zone where inundation excludes invasive species . This biotic manipulation can allow native species to reestablish, but the duration of weeding is often limited to the implementation phase due to financial constraints . Overall, the management challenges faced by restored vernal pool assemblages are tenacious and long-lasting, while most restoration projects are restricted to the short timescale of the implementation phase. To date, most research on vernal pool restoration has been focused on short-term measures of restoration success, but it is unclear how successful short-term interventions are in the long run. First, we conducted a 3-year study on a complex of pools that were transitioning from the implementation phase to the post-restoration phase during the study period. By evaluating changes in vegetation composition in these pools during this pivotal transition period, we asked: How did exotic plant abundance and richness change in these restored pools over time? How did native plant abundance and richness change in these restored pools over time? As restored pools receive less weeding and native planting over time, we might expect the reinvasion of exotic grasses from the surrounding grassland matrix. Our second approach involved a broad survey of 69 vernal pools from nine different restoration projects carried out over 33 years, which allowed us to explore how climatic and landscape conditions correlate with the abundance and diversity of plant species within restored vernal pools after the implementation phase. If exotic plant species reinvade vernal pools over time, we might expect various site landscape factors to influence the plant assemblages. For example, pools that experience more precipitation and/or have deeper basins may sustain longer inundation periods that favor more native species, while pools that have more edge area exposed to the exotic-dominated surrounding grassland may be more susceptible to invasion . We asked: What abiotic factors correlate with higher exotic plant abundance and richness in restored pools over time? What abiotic factors correlate with lower native plant abundance and richness in restored pools over time?We studied restored vernal pools on land managed by the University of California, Santa Barbara , the Isla Vista Recreation and Parks District, and the City of Goleta, in Santa Barbara County, California, U.S.A. . This land is part of unceded ancestral territory of the Chumash people. The study areas lie within 1 mile of the Pacific Ocean and experience a Mediterranean climate with cool and wet conditions from November to April and warm and dry conditions during the remainder of the year . Rainfall averages approximately 43.18 cm per year with high variation associated with extreme rainfall events and droughts. The proximity of the area to the Pacific Ocean moderates winter lows, and frost is rare. Summer fog moderates summer highs, although offshore “sundowner” winds may bring hot dry conditions to the area, especially in the late summer and fall . Soil formation is dominated by weathering of uplifted shales, and soils have a high clay content. Soils are Mollisols, with the dominant soil series being Concepcion fine sandy loam and Diablo clay .We monitored 7 restored vernal pools within UCSB’s North Parcel, which consists of vernal pools built amidst university faculty housing. The pools were created between 2011 and 2014 by grading to form pool basins ranging from 67 to 425 m2 in area and 14–18 cm deep . Approximately 70 species of locally-sourced native plants were introduced to pool basins, including species endemic to vernal pools and generalist wetland and upland species. Most species were introduced by planting seedlings in patches to mimic landscape patterns generally observed in nature, according to soil types, hydrology, and other site factors. Installed plantings were watered using movable drip irrigation and hand-watering until establishment was achieved. Some annual species were direct-seeded. Exotic species were mainly controlled by hand-weeding, although solarization, herbicide, and green flaming treatments were also employed to a lesser degree. All these restoration actions took place within a 5-year implementation phase. Within each restored vernal pool, we established a series of permanent monitoring quadrats. We delineated each pool into central , transition , and upland zones . Within each of these zones, we haphazardly placed three 1 m2 quadrats, for a total of 9 quadrats per pool. We monitored the vernal pools monthly from November 2016 to December 2019. Because the pools were different ages at the start of the experiment, sampling over 3 years allowed us to evaluate the vegetation community in pools ages 2–9 years old.

Biological control has primarily focused on insects that attack the flower heads. Only two insects have proven somewhat effective, including the hairy weevil and the false peacock fly , having been reported to reduce seed production . Revegetation with native or introduced grasses, legumes, or other forbs is an important component of long-term yellow starthistle management.Methods for controlling medusahead have been studied and implemented since the 1950s with the goal of reducing thatch buildup and reducing flowering and seed production. Control approaches have often targeted windows for burning when medusahead is still growing but when most associated species are mature and dry . Grazing management approaches have successfully reduced flowering on a small scale by targeting a narrow period just before the flower emerges in April or May . On a large scale, grazing has been less successful because of management challenges, including availability and distribution of water and availability of sufficient cattle numbers for targeted grazing in later spring and early summer . Glyphosate can be an effective control method when applied in early spring to young medusahead plants. However, it is non-selective and can damage desirable broadleaf or grass vegetation, including native perennial grasses at moderate to high rates. In the correct ecosystem, vertical farm equipment proper timing and low rates of glyphosate can control medusahead without damaging desirable perennial plants . Fall applications of aminopyralid at high rates have been shown to prevent medusahead germination throughout the season .

Barb goatgrass was first identified in California in the early 1900s, but it has spread rapidly in recent years. Barb goatgrass grows in dense stands supported by deep and rapidly establishing root systems that make it extremely competitive in annual rangelands. Davy et al. reviewed the biology and ecology of barb goatgrass, as well as control methods. Fire can be an effective method of control if repeated for 2 consecutive years . While no grass-selective herbicides are registered for rangelands in California, glyphosate is a practical and effective method for controlling selected patches. Mowing and grazing can be effective if heavy defoliation is applied just prior to seed head emergence. Invasive plants cause serious ecological damage to California’s wildlands, and successfully addressing this widespread problem requires an integrated approach. Effective control will require long-term management using combinations of biological, mechanical, cultural, and chemical methods . Integrated management may incorporate specific sequences of practices and approaches, including targeted grazing and permanent changes in grazing practices. Successful control will also require cooperation of private landowners and public agencies working within organized weed control areas.Klamath weed is not considered a large rangeland weed problem because its control in the 1940s was so successful. The importation in 1944 of Chrysolina quadrigemina and its close relative, C. hyperici, was the first North American attempt at controlling weeds with insects. The insects are natural enemies of Klamath weed, also known as St. John’s wort. This native European plant is a pest on rangelands throughout the temperate regions of the world because it displaces forage plants and is toxic to cattle and sheep. In 1943 it was estimated that 400,000 acres of California rangelands were infested with Klamath weed.

The beetles Chrysolina hyperici and C. quadrigemina were first released in 1945 and 1946, respectively. Both species became established, but C. quadrigemina proved especially effective for Klamath weed control. Populations of the beetles quickly grew and spread. After 5 years, millions were collected from original release sites for redistribution throughout the Pacific Northwest. Ten years after the first releases, Klamath weed populations in California were reduced to less than 1 percent of their original size , and the weed no longer threatens the livestock industry. From 1953 to 1959 alone, California saved an estimated $3,500,000 per year due to this biological control program .Seeding of improved forage species has been the primary means of improving productivity of annual grasslands and cleared or thinned oak woodlands and chaparral. Introduction of annual legumes and perennial grasses from the Mediterranean region, often by way of Australian forage improvement programs, has been an integral part of range improvement programs. Subterranean clover was introduced from Australia in the 1930s. Rose clover was introduced in the 1940s by Professor R. Merton Love of the Agronomy and Range Science Department . Smilograss , an Asian native grass, was introduced from New Zealand by Drs. E. W. Hilgard and E. J. Wickson in 1878. Hardinggrass was introduced from Australia by Dr. P. B. Kennedy shortly after his arrival at UC Berkeley in 1912. Later, summer-dormant orchard grasses and summer-dormant tall fescue were introduced for rangeland seeding. Bur clover is an annual medic that was introduced during European colonization of California. In the 1950s and 60s, it was joined by other annual medics from Australian breeding programs. Lana vetch was introduced for rangeland seeding in the 1950s by USDA Soil Conservation Service .Seeding of rose clover and subterranean clover to improve productivity on Mediterranean-type rangelands began in the 1950s. The primary effect of annual legumes on annual rangeland productivity is to increase winter and spring forage production and to improve the nutritional quality of the available forage. Table 1 compares protein and crude fiber content of legumes, grasses, and other forbs.

Gains of 150 to 300 pounds of beef per acre can be consistently produced on annual legume– improved ranges. In “good clover years,” this type of production is possible on clover alone. However, since good clover years do not occur every year, the introduction of annual legumes, including subterranean clover, rose clover, and annual medics is recommended. Maximum profit per acre results from paying careful attention to adequate soil fertility, seeding adapted varieties, ensuring proper inoculation at planting, and providing good grazing management.Subterranean clover, rose clover, lana vetch, and the annual medics are adapted to annual rangelands where elevations are below 3,000 feet and rainfall exceeds 15 inches. Rose and subterranean clover are most commonly used and grow well together on neutral to acid soils. The annual medics tend to be best adapted to neutral to basic soils. Several varieties of annual clovers and annual medics mature over a wide range of dates from very early to very late spring . Some subclovers are adapted to wet or poorly drained soils. Most fields to be seeded contain a variety of soils, so the seeding mixture should contain several varieties and types of clover. It should include both earlyand late-maturing varieties that are adapted to a variety of sites to ensure good forage growth during very dry winters or springs, as well as under “normal” conditions.Murphy et al. published guidelines for planting and managing annual legume seedings. Most lands planted to annual legumes are deficient in either sulfur or phosphorus, or both, so that adequate amounts are required to produce a good initial stand and to maintain maximum forage and seed production. While there may be a carryover effect the year after fertilization, commercial indoor growing systems especially from phosphorus applications, maintenance fertilization is necessary to maintain clover stands and productivity. Clovers need to grow in association with certain soil bacteria to provide the nitrogen they need for growth . In most areas these required strains of bacteria are not present in the soil and must be furnished by inoculating the seed with the right bacteria at seeding time. Well-inoculated clovers supply extra nitrogen to make the associated grasses more productive. The pellet method of inoculation is recommended. Some seedbed preparation is often necessary to reduce competition, ensure the survival of rhizobium bacteria, and provide for seed coverage; however, direct seeding in low residue has been successful in many locations. Seed can be broadcast or drilled, but it should be covered by about 0.5 inch of soil. Seeds may not emerge if they are placed deeper. Seeding rates are often around 10 to 20 pounds/acre. A broadcast seeding should be lightly covered by ring rolling or harrowing. Broadcast seedings that are not covered are highly susceptible to failure in marginal rainfall areas. Range drills are sometimes available from area seed companies. Seeding should be done as close to the first fall rain as possible and before cold weather. Fall seedings in October and early November are much more successful than December seedings. If germinating rains do not come before cold weather, delay seeding until the following year.Legumes stimulate the early growth of grasses and filaree.

In the winter and early spring, seeded ranges should be grazed to use the grass and prevent nonlegumes from crowding the clovers. Reducing grazing while clover is blooming will allow an adequate seed set. Stands should be heavily grazed during the summer and fall to make use of the dry feed and to trample the seed into the ground. More stands of clovers have been lost by grazing too light than by heavy grazing.Annual ryegrass is the main improved annual forage grass used on annual rangelands. With proper fertilization it can provide high-quality forage during the growing season, and it remains an important species for improving forage quantity and quality. Annual ryegrass germinates rapidly and is able to quickly stabilize soils following burns and other disturbances. Unfortunately, this characteristic also makes annual ryegrass a strong competitor to native species. Consequently, it has been listed as an invasive non-native plant that threatens wildlands by the California Invasive Species Council. If your goal is to maintain and increase native grasses and forbs, excluding annual ryegrass is a legitimate management practice. However, if you need to stabilize soil quickly or you are seeking improved forage, seeding annual ryegrass remains an important agricultural practice. Like annual legumes, annual grasses should be seeded just prior to the fall rains. Annual grass seeds are small and should not be buried too deep when seeding. Seed can be broadcast or drilled, but it should be covered by about 0.5 inch of soil. Seeds may not emerge if they are placed deeper. It has generally been recommended that seed be drilled with a grassland or rangeland drill into existing but closely grazed stubble from the previous growing season. If a drill is not available, the soil should be lightly disked or harrowed to loosen the top 1 inch of soil and seed broadcast on the soil surface. Broadcasting should be followed by light rolling or dragging to cover the seed. Annual grass seeding rates are frequently about 5 to 10 pounds/acre. Blando brome and Zorro fescue are also available for seeding for erosion control. Soft chess brome is a desirable forage species that is naturalized and widespread on annual rangelands. Both of these grasses were selected from wild populations and developed into commercial varieties by the USDA NRCS Plant Materials Center.Seeding native or introduced perennial grasses into annual rangelands has always been challenging, with failure being more frequent than success. Competition from annual grasses and forbs during seedling establishment is a major source of failure, but improper grazing of successful seedings has also been a source of stand loss. The primary reasons that ranchers have seeded perennial grasses on annual rangelands is to provide a higher amount of winter feed and green feed several weeks later in the season than the naturalized annual grasses and forbs. Hardinggrass and some other perennial grasses have the ability to break summer dormancy and begin growth before the first fall rains and remain green until after seed has matured in early summer. This can add several weeks to the green forage season. However, when seedings are successful, establishment sometimes takes 3 to 5 years before perennial grasses are able to compete with annual grasses. Consequently, perennial grass seedings have not been widespread on annual rangelands, with most success being along the high-rainfall north coast. From 1937 to 1951, the University of California Extension Service and Agricultural Experiment Station planted thousands of test plots to determine what grasses were adapted to seeding following brush burns and other woody plant control. Planting methods and seeding recommendations were developed for the annual rangelands and intermountain areas where rainfall exceeded 10 inches . Hardinggrass was seeded in many counties, and remnants of those plantings can still be found. However, McKell et al. found that grazing during active growth reduced yields and increased mortality. Likewise, ranch managers have reported low persistence of grazed stands in all but the very best soils.

Recovery times tended to be longer for R. crispus compared to other weed species, particularly when fed to growing heifers .All main effects and their interactions were significant for the seed viability and recovered viable seed measured over the four consecutive dates . The highest value of total recovered viable seed was observed with S. halepense when fed to lactating cows but was not significantly different from P. aviculare in this group and growing heifers. It was minimal in R. crispus when fed to dry cows . For all weed species , recovered viable seeds showed a consistent decreasing trend with feedlot lactating cows > growing heifers > feedlot male calves > dry cows. Averaged over the four cattle groups, the most persistent seeds were P. aviculare with 52% viability of fed seeds, the least persistent fed seeds were those of R. crispus with 32% viability . The power model provided adequate fits to viability data over time . Seed viability declined with time after seed intake, however, the rate and magnitude of reductions varied across weed species and cattle groups . There were few changes in seed viability during the initial times for growing heifers and dry cows, whilst viability loss was more rapid in other cattle groups . We also estimated the half-life of seeds fed to different cattle groups using Eq 5. The half-time, tV50, varied from 62 h for R. crispus in lactating cows and feedlot male calves, vertical grow rack to 82 h for P. aviculare in dry cows . All weed species had a longer half-life when fed to dry cows and growing heifers, as shown by larger tV50 values .

Seed mortality was fastest in feedlot male calves, where seeds had a half-life of 64 h. Although this parameter indicates higher seed mortality in feedlot male calves than growing heifers, but the total recovered viable seed was greater in growing heifers . The relationship between seed recovery and viability was curvilinear and showed a predictable pattern over time. Recovery was highly variable for the first two sampling days, ranging from 2% to 50%, and these seeds had viabilities as high as 70% to 100%. Conversely, for sampling 3 and 4 days after intake, the daily seed recovery was less variable but did not exceed 20%, while seed viability was highly variable and ranged from 0% to 70%. By four days after seed intake very few seeds were recovered and the majority were dead . A significant positive correlation was found between seed viability and ruminal pH with r = 0.86 . The pH was higher in dry cows and growing heifers than in feedlot male calves and lactating cows, and was also associated with higher seed viability.This study showed that seed recovery and viability, as well as passage time through the digestive tract, can differ markedly between cattle types of the same livestock species. However, not all weed species showed a similar response. The passage time and ruminal retention time of feed are determined principally by the frequency and amount of feed consumed, forage physical form, concentrate/forage ratio and forage fiber content. Bodmer & Ward found a positive linear relationship between seed survival and animal body size, however, our higher seed recovery observed with growing heifers and feedlot male calves with small body sizes, rather than with dry cows with large body sizes. It seems that the amount of feed intake is more important than the body size.

The amount of feed intake for lactating cows was approximately twice as much as that of the other cattle groups . Increasing the amount of feed reduced the retention time while accelerating the flow through the reticulo-rumen, which in turn resulted in high seed output rate as observed in lactating cows . Furthermore, diets with a high digestibility, i.e. with higher concentrate/forage ratios and lower levels of neutral detergent fiber , and acid detergent fiber pass more quickly through the digestive tract of ruminants. For example, in lactating cows, such higher digestibility can result in higher seed recoveries than in other cattle groups . In our study, although concentrate/forage ratio was much lower in growing heifers, seed recovery in this group was higher than in feedlot male calves . Only 10% of ingested seed was recovered with low-digestibility diets compared to 28% with high-digestibility diets in sheep. Wheat straw, which constituted 34% of the diet in dry cows , can encourage chewing and increase ruminal retention time due to its high fiber content. The recovery of seeds also varied among weed species, which can be attributed to their differences in physical characteristics . Gardener et al. found a strong positive correlation between the specific gravity of seed and the rate of passage through the digestive tract of cattle, however, seed size was only weakly positively correlated with the passage time. We found lower seed recovery in R. crispus than S. halepense despite the two species having seeds of the same size . However, this difference in recovery can be explained by the differences in specific gravity between the two seed types, in that S. halepense seeds have a higher specific gravity than those of R. crispus and thus were recovered in higher numbers. Small seeds are expected to have a pattern similar of rate passage to that of the liquid fraction in a fermentational bag, whereas large seeds are expected to have the pattern similar to that of particulate matter. Thus, specific gravity has a greater influence on the rate of passage of small particles than that of the sieving effects of the mass of reticulo-rumen. In all cattle groups, the highest seed recovery occurred two days after seed intake. Gökbulak also reported a similar peak time in Holstein heifers for seed recovery from three perennial species and two forbs species. The length of time for 50% recovery of tropical pasture seeds after intake average over the ruminants has been measured to be about 51–71 h and in cattle it was 34–51 h. The recovery rate for undamaged seed depends on the chewing style, which varies between ruminants, with sheep and goats causing more damage to seeds than cattle. These results demonstrate that a wide range of seed excretion rates is likely to happen because of differences in animal diet and seed characteristics. Several studies have demonstrated that the viability of excreted seeds declines with the length of time seeds spend in the digestive tract. The seed coat and degree of seed hardness and dormancy are important factors in determining the viability of seeds passing through the digestive tract. Initial seed germination was lower in the three species with higher viability than in R. crispus, which had an initial germination as high as 87%. Impermeable seed coat of C. campestris prevents germination leading to physical dormancy in this species, which may help it to survive the passage. These results suggest that seeds with higher dormancy could probably be more resistant to digestion. However, commercial vertical hydroponic systems to test this hypothesis one needs to use seeds that vary in the degree of dormancy only but no other traits e.g. seeds from the same species but with different dormancy levels.Feedlot male calves and lactating cows caused higher seed mortality than dry cows and growing heifers , whereas total recovered viable seed was highest in lactating cows followed by growing heifers . Ruminal pH varied from 6.2 for feedlot male calves to 7.4 for dry cows at 0700 h before the morning meal . A high feed intake as ad libitum, especially with a high level of concentrate, can cause fluctuation in ruminal pH, ammonia and volatile fatty acids concentrates. Furthermore, a high proportion of wheat straw in dry cow diets can increase total chewing time, which in turn can lead to an increase in buffering conditions in the rumen. The level of NDF has a positive effect on increasing chewing activity and rumen buffering. These factors might have led to more seed loss observed in feedlot male calves and lactating cows over the third and fourth days after the seed intake.

It seems that the timing of seed excretion is the preliminary factor affecting the seed survival whilst other factors such as pH and NDF became important once seeds persist in the digestive tract for a longer period. For example, lactating cows and growing heifers excreted a high amount of seeds within the first two days after feeding: this rapid excretion rate resulted in high total survival rate . As lactating cows exhibited the highest recovered viable seeds , this group of Holstein cattle is more likely to infest cropland with manure rich in weed seeds than other cattle types. However, this hypothesis is based on the assumptions that weed seeds are distributed uniformly across all the feed types offered to cattle. Common practice in formulating cattle diets is based solely on the nutrient requirements of the herd and on production goals. However, if the manure of the cattle is to be used on farmlands, the risks associated with the spread of weed seeds from that manure also need to be considered.Horseweed and hairy fleabane are summer annuals belonging to the Asteraceae family. The temperature and light requirements for germination, soil type preference, and depth of soil emergence of these two species are fairly similar. The optimal temperature for germination of both species ranges from 65ºF to 75ºF, and they can germinate under moderate water stress. However, hairy fleabane can germinate at lower temperatures than horse weed . Some germination of hairy fleabane has been recorded at temperatures as low as 39.5ºF . Although both these species can germinate under complete darkness, greater germination occurs under light . Nanudula et al. found greatest germination of horseweed under a 13-hour day length. Based on these characteristics, conditions are ideal for horseweed and hairy fleabane germination in mid to late fall and late winter in the Central Valley. Therefore, we often see seedlings emerge multiple times during the year in the Central Valley . Under some conditions, horseweed seeds can germinate year-round .Seedlings that germinate and emerge in late fall can overwinter as a rosette and then bolt in spring. Emergence of these two species is greater and more rapid in coarser than in finer soils , and germination is greater in soils with a neutral to alkaline pH range than in acidic soils . However, horseweed has been observed in great numbers in the acidic to neutral soils of the southeast Central Valley. Seedling emergence is primarily from the soil surface, and no seedlings emerge from depths greater than 0.2 inch . The seeds and seedlings of these two species look very similar and are very difficult to distinguish. The characteristic features, at the seedling stage, that may help in distinguishing the two are that the leaves of horseweed are dull green, oval, and have fine, short hairs, whereas the leaves of hairy fleabane are gray-green, narrower, and more crinkled . Seedlings of these two species can also be confused with common winter annual weeds such as common chickweed and shepherd’s-purse . Horseweed and hairy fleabane plants are difficult to distinguish from each other until about the 12-leaf stage. Once the plants bolt it is easy to differentiate the two species. Horseweed bolts, sending up a single, or primary, vegetative stem that is erect with dark green leaves that are up to 4 inches long and are crowded together with an alternate arrangement on the stem . The stem is smooth or covered with shaggy hairs. Hairy fleabane, unlikehorseweed, develops multiple lateral branching without a central stem and has leaves that are much narrower with stiff hairs. The distance between the leaves is greater in hairy fleabane than in horseweed . At maturity, horseweed is usually much taller than hairy fleabane. Horseweed can be 10 feet tall, whereas hairy fleabane is usually 1.5 to 3 feet tall . Both species usually start flowering in July and produce small, yellowish flower heads at the terminal end of branched stems . Occasionally, in Tulare County, hairy fleabane has been observed to flower as early as mid-March. However, the factors responsible for this earliness are not known. Horseweed plants can produce more than 200,000 tiny, narrow tan-colored seeds . In some cases, horseweed seeds have been found up to 300 miles away from where they were produced .

Although currently there are no standards in the United States to separate government-approved biotechnology traits, 1 percent adventitious presence has been suggested as the standard for adventitious presence of biotechnology-derived traits in non-transgenic varieties of seed crops in export markets. Handling of RR alfalfa seed may also require additional checks in place to prevent co-mixing of transgenic and conventional seed, depending on the market destination of the seed. For a review of crop identity preservation, see Sundstrom et al. 2002.Hundreds of alfalfa varieties have been developed for use in North America using conventional breeding methods of crossing and selection. These varieties are adapted to the major alfalfa production zones and contain important genes for high yield, resistance to diseases, insects, and nematodes. Growers have been the beneficiary of decades of plant breeding by public institutions and private companies and competition between seed companies for their business. Several alfalfa seed companies will likely be marketing RR alfalfa varieties to satisfy a range of market conditions. Although Forage Genetics International has developed the initial RR alfalfa cultivars, other alfalfa breeding companies will have access to the trait. Fall dormancy is a major criterion for variety selection. In the first few years of release of the RR technology, the selection of varieties is likely to be limited to varieties within a small range of fall dormancies, vertical farming systems for sale with other fall dormancy classes to follow in subsequent years.

With the introduction of the RR trait, variety selection will include consideration of yet more “value-added” traits that should be considered in addition to yield and other traits. Generally, the protocol for selection of RR lines does not differ significantly from the selection of conventional lines. Fall dormancy group, yield potential, disease and insect resistance, and forage quality should all be considered, in addition to the value of the herbicide resistance. Calculations of potential benefits from the weed control technology should be compared to the added cost of the seed, relative costs of herbicide strategies, and potential limitations of the technology.Recommendations for seeding rates vary significantly across the United States. California currently recommends a range of 15 to 25 pounds per acre of seed, depending on seeding method and soil preparation. Although the price of seed is typically less than 2 percent of the total cost of production for growers, as the value and cost of seed increases, the relative economic impact of seeding rates and method increases. Precise seeding methods combined with proper soil preparation allow good control of seeding depth, seed placement, and soil-seed contact. Irrigation and early weed control during stand establishment reduce the probability of stand failure. These practices may enable growers to lower seeding rates, and thus manage cost of seed for higher-value genetics.Enhancing Weed Control Options Current technology controls most but not all weeds. Certain weeds, such as Canada thistle , dandelion , dodder, nutsedge, bermudagrass, , and quackgrass are particularly problematic. Annual weeds such as barnyardgrass , pigweed, lambsquarters, foxtails , nightshades, downy brome , and mustards can be troublesome at certain times. A subset of these weeds can be controlled by a combination of currently available herbicides in tank mixes or multiple applications, but Roundup controls a broader weed spectrum and may be more efficacious than most currently available herbicides or herbicide combinations .

Weed Control Flexibility While many available weed control options have fairly well-defined requirements and restrictions as to application timing, temperatures, and environmental influences, Roundup strategies are likely to provide a more-flexible option to growers. Although timing with Roundup applications is to some degree still important, it may not prove as important as it is with some of the alternative methods. The high degree of flexibility and broad-spectrum weed control are the principal benefits of RR alfalfa. Potential Economic Benefits Roundup Ready technology has the potential to provide more-reliable stand establishment and improve alfalfa yields and forage quality due to reduced weed contaminants. The value of alfalfa per ton may be improved, since pure alfalfa is usually worth 20 to 50 percent more than weedy hay. Other possible benefits include extended life of stands and improved crop safety compared to other weed control options. However, as of this writing, the economic benefits of the RR technology are not entirely clear, since the pricing structure has not yet been determined. Animal Feed Safety and Animal Health Contamination with poisonous, antinutritional, or simply unpalatable weed species is a common hazard of livestock feeding. Veterinary diagnostic labs and veterinarians each year report many cases of horses, cows, and sheep that are killed or sickened after consuming alfalfa that has been contaminated with such weeds. Some weeds simply lower animal performance or milk production, but others can kill. Roundup Ready alfalfa provides a simple option to minimize the risk of consumption of poisonous or unpalatable weeds by livestock, and it has the potential to improve animal welfare and production by increasing the feeding of pure, weed-free, high-quality alfalfa hay. Water Quality In addition to the benefits in terms of crop productivity, crop quality, animal production, and value, RR technology may replace some herbicides that have the potential to contaminate water supplies. Several herbicides used in alfalfa during the winter period have been detected in wells in California’s San Joaquin Valley . To the extent that it replaces those options, RR technology could lessen this environmental concern, since there is little evidence of off-site environmental impacts from glyphosate . Preventing Spread of Noxious Weeds Although all successful weed control strategies share this characteristic, RR alfalfa could improve the ability of growers to slow or stop the spread of noxious weeds in hay. The U.S. Forest Service and other agencies have encouraged the use of certified weed-free hay to be brought into natural areas for livestock and pack horses to prevent the spread of noxious weeds into environmentally sensitive areas. Roundup Ready technology could aid in that effort by creating “weed-free” alfalfa hay.Weed Control Limitations Although the spectrum of weeds controlled by Roundup is impressive, certain weeds are not completely controlled by Roundup. These include cheese weed , burning nettle , filaree , and others. In addition, Roundup has no residual activity that controls weeds for longer periods, as some conventional herbicides do. Roundup Ready technology should not be viewed as a panacea, vertical farming equipment but as a component of an overall weed control effort on a farm. Weed control strategies that incorporate cultural methods and rotation of herbicides will be needed to combat weeds not completely controlled by Roundup in order to prevent weed shifts. Herbicide Resistance One environmental concern about RR technology is the development of herbicide resistance in weed populations. This becomes more of a concern as the acre treated with Roundup increases. Since RR technology already encompasses many crops , it is very likely that tens of millions of acres will be treated with Roundup each year nationally.

Evidence for Roundup resistance has already been identified in natural populations in some species, such as ryegrass  and horse weed . It is possible that this might occur in other species. This problem is not unique to Roundup but is common for other classes of herbicides as well. The development of weeds with resistance to Roundup is thought to be less likely than for other herbicides, as Roundup has no soil residual activity, and Roundup has a unique mode of action. Herbicide strategies that incorporate integrated cultural methods and rotations of herbicides are needed to prevent herbicide resistance. This is especially important to control volunteers of subsequent herbicide resistant crops. Weed Shift A weed shift is a change in the relative frequency of weeds in a population in response to a management practice. In the case of herbicides, weed shifts occur when a herbicide does not kill the entire weed spectrum encountered in a field. The density of the weed species that is not controlled increases over time, resulting in a weed shift. While Roundup is perhaps the most broad-spectrum foliar herbicide available, it is not equally effective on all weeds. Roundup is less effective for the control of many common weeds, such as cheese weed, burning nettle, filaree, and purslane. Over time, if Roundup is used repeatedly as the only weed control measure, the prevalence of these weeds is likely to increase. This has already been observed in a trial in San Joaquin County, where burning nettle was not adequately controlled with Roundup , and the population of this weed has increased significantly over a 3-year period. As with herbicide resistance, the best practice to prevent weed shifts is to avoid using the same herbicide year after year and to rotate herbicides and crops, as well as using non-herbicide strategies to control weeds. Gene Flow to the Environment As the RR gene is new to alfalfa, its effect on the environment must be studied in the context of gene movement and persistence in plants. Genes introduced through biotechnology are passed on from generation to generation and to and from close relatives as any other gene in plants. It is important to establish strict management protocols to ensure varietal purity and minimize gene flow to and from unwanted sources, also known as adventitious presence. Gene flow is affected by sexual compatibility, flower characteristics, pollen viability and quantity, proximity of neighboring plants, pollinator activity, and environmental conditions. In the United States, there are no sexually compatible wild relatives to alfalfa; feral alfalfa is the only plant it can successfully cross with.The potential environmental impact of the gene flow from RR alfalfa to feral alfalfa must be understood in terms of “fitness.” Alfalfa generally is not considered by weed scientists to be an invasive weed, but it does occur along roadside ditches and in agricultural areas. If the RR gene is transferred to feral alfalfa, it is not clear that these plants would have any natural advantage over conventional alfalfa, or any greater weedy characteristics, except where Roundup is sprayed. Research is currently being conducted by University of California scientists to determine the proper weed management programs to prevent outcrossing and to control feral alfalfa. As our alfalfa removal studies have shown, several commercial herbicides are currently available for removal of RR alfalfa. For the 22 million acres of alfalfa in the United States, the issue of crossing RR alfalfa with feral relatives may not be a major issue, since these fields are typically harvested in the prebud to midflower stage of development, thus little pollen flows and few viable seeds are set . The issue of gene flow is primarily a concern in seed production, where pollen flow is necessary for seed set. Currently, less than 0.5 percent of the alfalfa grown in the United States is grown for seed. Market Acceptance of Roundup Ready Hay Roundup Ready alfalfa will be the first genetically enhanced alfalfa product to be marketed commercially. It is anticipated that the first commercial crops will be grown in 2005. In most parts of North America, the majority of alfalfa is fed on-farm, but in the western United States, the majority of hay is offered for sale to dairy, with the remainder to horse, beef, and export customers. Nationwide, most alfalfa is consumed by the U.S. dairy industry, where it is considered the premier forage crop. For example, in California, dairy cows consume greater than 75 percent of the state’s alfalfa crop. Thus, consumer acceptance of RR hay is highly dependent upon the acceptance of the dairy industry, which in the last decade has absorbed four to six new technologies related to genetically modified crops. Because of this, most experts believe that the dairy industry will, by and large, accept RR alfalfa. The horse industry may provide initial resistance, since individual preferences come to the forefront, but some buyers may be attracted to the “weed free” aspect of RR alfalfa. The organic market for hay is small and will likely reject RR alfalfa, as it does other biotech crops. Except for some specific markets such as organic, most alfalfa experts do not foresee significant market resistance to RR hay, with the exception of the export market. Exports The United States exports about 4 percent of its alfalfa to Japan, Korea, Taiwan, Mexico, and Canada. About 80 percent of U.S. alfalfa hay exports are destined for Japan , with approximately one-quarter shipped through California and three-quarters shipped through Oregon and Washington ports .

Given the high germination rates for all cultivars, the consistently greater index for M-209 reflects a greater degree of apparent vigor for that cultivar. Greater than 75% of seedlings emerged from 2.5 cm, 5.1 cm, and 7.6 cm planting depths after 8 DAP, 10 DAP, and 14 DAP, respectively. Consequently, below-soil elongation data reported are for up to those dates only. Total below-soil elongation over time of each cultivar followed a similar pattern for each seeding depth: M-209 tended to the most rapid elongation, followed by M-205, M-206, and M-105, respectively, in decreasing relative elongation rates. For each cultivar, total elongation by 8-10 DAP was no different regardless of planting depth , suggesting that total cultivar elongation ability was independent of effects of planting depth under the study conditions. Turner et al. similarly found that depth did not play a role inelongation rates of either coleoptiles or mesocotyls of semidwarf or conventional rice in well watered soils. M-205 and M-209 total elongation rates were unchanged from 10-14 DAP at 7.6 cm depth, while M-105 and M-206 total elongation rates slowed by 69% and 71%, respectively. Coleoptile elongation was also similar for each cultivar at 8 DAP for all planting depths, yet by 10 DAP at 7.6 cm depth, differences between cultivars became more apparent . Interestingly, industrial drying rack coleoptile elongation slowed for all cultivars after 10 DAP at 7.6 cm depth, regardless of coleoptile length or the relative soil depth of coleoptile tips.

M-205 coleoptile length at 7.6 cm planting depth only increased 2% from 10 to 14 DAP, yet its mesocotyl length increased more than threefold over the same period, resulting in a nearly linear total elongation. Mesocotyl elongation rates increased for all cultivars after 8 DAP at the 5.1 cm and 7.6 cm planting depths . Irrigation occurred at 8 DAP, therefore it is possible that increased plantavailable water enhanced cellular expansion after that date, however it is also possible that a decrease in available O2 subsequent to soil saturation may also have contributed to the rapid increase in mesocotyl elongation. Rice coleoptile elongation is well known to be enhanced by hypoxic or anoxic environments due to heightened α-amylase activity and fermentative metabolism , yet research detailing mesocotyl elongation in response to hypoxia is less common. Raskin and Kende found that hypoxia increased elongation of both coleoptiles and mesocotyls, though Huang, Greenway, and Colmer only observed mesocotyl elongation enhancement under anoxia that was present at imbibition, as opposed to anoxia imposed several days afterward. In this study, mesocotyl lengths were far more variable than coleoptiles between cultivars at any depth, and between depths for a given cultivar and DAP. For example, observed mesocotyls were far shorter at 8 DAP for all cultivars at 5.1 cm and 7.6 cm depths, compared to the same DAP at 2.5 cm planting depth . However at 10 DAP mesocotyl elongation was similar for all cultivars at both 5.1 cm and 7.6 cm depths. Beyond 10 DAP, mesocotyl elongation for all cultivars at 7.6 cm depth proceeded relatively linearly, with M- 205 having the most rapid elongation at 0.31 cm / day, and M-206 having the slowest at 0.05 cm / day.

M-209 had significantly greater total and coleoptile lengths than the other cultivars, , yet M-205 and M-209 had no differences in final mesocotyl lengths , though both of those were significantly longer than the other cultivars’ mesocotyls. It has been previously reported that semidwarf rice cultivars do not establish well under deeper seeding, compared to conventional-stature cultivars. Earlier research demonstrated a correlation between mesocotyl length and vigor in semidwarf and taller cultivars . Semidwarf cultivars tended to have shorter mesocotyl length, as well as reduced stand establishment and reduced early-season growth rate when seeded at greater depths. However, McKenzie et al. found that crosses of a semidwarf line with a conventional line showed no difference in seedling length between semidwarf and taller descendants, but all seedlings were significantly longer than the semidwarf parent. More recently, Ju et al. found that several semidwarf cultivars had higher rates of mesocotyl elongation than conventional lines, and two long-mesocotyl semidwarf lines had the highest emergence percentages from up to 6 cm soil depth. In the present study the final mesocotyl lengths for all cultivars at the deepest planting were 1 cm or greater. The relative proportion of mesocotyl length to total length by 14 DAP at 7.6 cm depth was 0.19 – 0.2 for all cultivars except M-205, which hada mesocotyl – to – total length ratio of 0.25. It is unclear why M-205 had a greater proportional mesocotyl length, though the present results suggest that the increased mesocotyl elongation rate may provide some vigor advantage over M-105 and M-206.Rice seedlings began to emerge by 4 DAP at 1.3 and 2.5 cm depth plantings, and by 5 DAP at all deeper plantings. However, at 7.6 cm depth only M-209 had any emergence until 8 DAP. M-205 and M-209 tended to emerge earlier and more rapidly than the other cultivars, across planting depths . In 2.5 cm plantings, M-105 and M-206 had more rapid emergence rates around T50, although at deeper plantings, M-205 and M-209 generally had larger b and smaller T50 values, indicating early and rapid emergence from 3 cm or greater planting depth for those cultivars. Overall, M-205 and M-209 had the lowest time to 50% emergence for all depths except surface plantings.

Plotting the reciprocal of e against planting depth revealed consistently greater emergence rates for M-205 and M-209. These values decreased linearly with depth for all cultivars, however the slopes of M-205 and M- 209 were less steep than for M-105 and M-206 . Traits conveying higher seedling vigor would be expected to contribute to earlier and more rapid crop emergence , thus contributing to synchronous stand emergence and development. By these measures, high vigor traits seen here in M-205 and M-209 should facilitate early-season crop and weed management . There were no significant differences in total emergence between cultivars seeded on the soil surface, but differences in total emergence became apparent between cultivars when seeded atany below-surface depth . Total emergence was greater than 95% for all cultivars at 1.3 cm and 2.5 cm planting depths, and all cultivars showed decreasing total emergence as burial depths increased . Reductions in total emergence from 1.3 cm to 7.6 cm depths were greatest for M-105 and M-206 at 79% and 76% respectively, followed by M-205 and M-209 at 56% and 38%, respectively. Relative growth rates of emerged seedlings were similar over time, however M-205 and M-209 were taller than the other cultivars at 0 cm, 6.4 cm, and 7.6 cm depths from 2 WAP onward . Total 8 WAP height responses to seeding depth were varied. Between 5.1 cm and 7.6 cm M- 105 and M-206 heights decreased 8.8%, and 4.9%, respectively. In contrast, M-205 and M-209 plant heights increased 5.2% and 5.7%, respectively, drying rack cannabis between 5.1 cm and 7.6 cm depths. Seeding depth had no effects on the length of time to first tiller appearance for any cultivar, though M-205 and M-209 had somewhat higher tiller numbers at each depth over time. At all depths M- 205 and M-209 increased tillers at greater rates than the other cultivars, yet tillering at 8 WAP was only significantly different at 6.4 cm and 7.6 cm depths . It is interesting that tiller initiation and total tillers were largely unchanged across depths, and that M-205 and M-209 saw tillering increases at the greatest depths. Reductions in tillering and plant height with increased crown soil depth are well documented in other cereals. Hucl and Baker found slight but non-significant reductions in rate of tiller emergence and total tillers plant-1 with increasing crown depth from 3 cm to 6 cm in Canadian spring wheat, and studies on European wheat and barley cultivars saw decreases in full-season tillering and height at depths greater than 5 cm . In contrast, other studies found slight increases in wheat tiller number from 3 cm to 6 cm planting depths , and from 5 cm to 10 cm planting depths , although tillering decreased with greater planting depths in both cited studies. It is possible that the observed tillering and height accumulation advantages of M-205 and M-209 would be transient if this study progressed to heading or grain harvest. By way of example, cultivar-specific advantages in above ground growth rate early in the season would be expected to be overcome by the time of heading, as final plant height is generally a fixed characteristic of a cultivar .

However, in this study we saw that M-205 and M-209 had greater rates of below ground elongation overall, as well as greater above ground height and tiller number over time at the deepest plantings. This suggests that these cultivars, though able to mobilize seed reserves to elongate and emerge more quickly, did not suffer for their early vigor in comparison to the less vigorous cultivars in the study. The data on height and tillering responses observed in this study are insufficient to predict whether these cultivars would respond similarly in the field; however, further studies on the effects of increasing crown soil depth on these cultivars’ growth and development at a field scale should shed light on these characteristics, and their potential effects on yield. Leaves per plant only differed where tiller number was significantly different. No differences were found in leaves per tiller across all cultivars and depths . Dry weights at each depth were only significantly different between cultivars at 0 cm, 6.4 cm, and 7.6 cm depths , and likely reflected the combined effects of final height and tiller number. Cultivar dry weights across were no different between 1.3 cm and 5.1 cm plantings. Between 5.1 cm and 7.6 cm planting depths, M-105 and M-206 dry weights were reduced by 45% and 50%, respectively, whereas M-205 and M-209 dry weights increased by 31% and 58%, respectively.Direct comparisons between below-soil elongation and parameters of emergence and development were not possible in these studies. However, our observations of differences between cultivars in seedling organ elongation and early-season growth parameters generally agreed with previous research linking elongation to rates of emergence, height, or tillering . As new cultivars are developed, seedling organ elongation rates might be used to by breeders to identify seedlines that are well-suited to the stresses of deep dry seeding. Our combined findings suggest that the observed vigorous characteristics of M-205 and M-209 seedlings should allow them to emerge rapidly and evenly several days after planting, if drilled to depths greater than 3 cm the field. This in turn would facilitate the usage of a stale seedbed technique without a delay of planting, and allow the application of non-selective herbicides to control early-emerging and resistant weeds without damaging emerging rice. In addition, if M-205 and M-209 demonstrate vigorous early growth and tillering in the field, that may hasten canopy closure, potentially conferring an additional competitive advantage over later-emerging weeds.Mechanized direct-seeded cultivation of rice is growing as a proportion of total area planted to rice around the world . Direct-seeded rice systems generally fall into the broad categories of dry-seeding or water-seeding. Dry-seeded rice can be broadcast onto dry soil by seed spreader or sown directly into soil by mechanical drill, whereas water-seeded rice can be broadcast into flooded fields by seed spreader or aircraft . Although direct-seeding of rice can significantly reduce time and labor investment in the planting stage, the various establishment methods described generally ensure that rice and weeds germinate and emerge synchronously , and weed management thus becomes largely dependent on chemical interventions . Herbicides can further reduce time and labor costs for weed management, however injudicious application techniques or over reliance on very few key active ingredients often result in the development of herbicide-resistant weed biotypes . As mechanization continues to be adopted in the rice sphere, integrated approaches to weed management are becoming more and more crucial. Rice grown in the Central Valley of California, USA comprises approximately 200 000 ha of irrigated fields. The region, which is among the highest-yielding in the world for rice production , is characterized by hot, dry, summers with abundant sunshine, and supports a single crop per year . California rice growers predominantly use a WS system, wherein pre-germinated seed is sown by aircraft into flooded fields. Rice seed sink to the soil surface and root down, emerging from the water after several days.

The restoration of urban creek ecosystems is tremendously challenging: human community needs , heavy pollutant inputs, hydrologic alterations, and frequent disturbance complicate management and make many noble restoration goals infeasible . One significant challenge that many restoration projects face is that of invasive non-native plant species , an issue that can be particularly pronounced in urban areas due to the connectivity of urban centers in an increasingly globalized world . Restoration of native flora is frequently cited as a goal in restoration projects , but can be exceedingly difficult. Removing invasive species without effectively establishing other desired species leaves a “weed-shaped hole” that non-natives can quickly re-colonize , . Though the hope behind earnest non-native removal efforts is that native species will re-colonize the area once niche space becomes available, the evidence that this occurs without further intervention is limited , particularly if the native species have been extirpated from the area and thus propagule material does not exist. Funk et al. propose the concept of “limiting similarity” to reduce the possibility of re-invasion by non-natives . The idea is that non-invasive native species that have similar functional traits to non-natives are expected to be better competitors and prevent the reinvasion of non-native species . ‘Functional traits’ are species’ attributes relating to how the species takes up resources and its effect on the resource pool in the ecosystem .

The limiting similarity concept encourages practitioners to fill the ‘weed-shaped hole’ with native species that will prevent non-native invaders from accessing resources in the ecosystem. Nitrogen is a critically important resource in ecosystem management. Nitrogen deposition has been implicated in facilitating invasion of nutrient poor California ecosystems by non-native plant species, rolling benches for growing particularly near urban areas with abundant fertilizer use and combustion-powered machinery . Furthermore, nitrogen has the potential to cause eutrophication of downstream waterways if it is provided in excess by urban runoff . This work builds off of Cadenasso et al. in that I suggest urban riparian restoration plantings as a method to prevent nitrogen pollution of the watershed. In this article I operationalize limiting similarity in the context of a working, volunteer-based restoration project on the University of California – Berkeley campus. Plant functional traits were measured to filter the regional species pool to a set of native plant species best suited to achieve desired project goals, namely to prevent re-invasion by non-native ivy species , and to prevent nitrogen pollution of the creek and riparian habitat. Within the broader trait-filtering framework, I hone in on the selection of native species with high rates of nitrogen uptake, as determined by a stable isotope tracer analysis. Enhancing riparian nitrogen uptake has the potential to both slow the rate of nitrogen delivery to the stream and help prevent re-invasion of riparian habitat by nonnatives . Finally,this research serves as an example of the sort of collaboration encouraged by Palmer , in which campus scientists inform the work of an ‘on-the-ground’ restoration program, which can then provide feedback with regard to the success of different approaches.

Strawberry Creek is an urbanized watercourse that runs east to west through Berkeley , California, from the Berkeley Hills to the San Francisco Bay . The creek has two forks that converge near the west entrance to the UC Berkeley campus . The 4.7 km^2 watershed drained by the creek is relatively undisturbed in the hills east of the campus, but is for the most part heavily urbanized, with impervious surfaces becoming the norm as the creek flows west through the flat lands of Berkeley . The creek flows in underground culverts for the majority of its path, including immediately east and west of the UCB campus. This study focuses on the reaches of the creek within the confines of the UCB main campus, to match the spatial scope of the work done by the partner restoration program. The establishment of the university along the banks of Strawberry Creek led to substantial degradation of its aquatic and riparian habitat. Trash dumping, sewage discharges, and campus lab waste made the creekatoxic siteformostofthe20thcentury . The creek’s course and riparian habitat were substantially modified to prevent flooding of campus buildings, which has led to significant incision and channelization .In the late 1980s,the Strawberry Creek Restoration Program was born, which led to substantial water quality improvement and native fish reintroduction to the creek . Understory habitat at Strawberry Creek is dominated by English and canary ivy , both non-native, invasive species. In recent years, the SCRP has shifted its focus to student-led, volunteer-driven understory vegetation management; perhaps the program’s biggest impact has been the removal of vast swaths of ivy from the shores of the creek. Other invasive species like periwinkle and panic veldtgrass have also been removed, which has resulted in largely unoccupied understory habitat for substantial stretches of Strawberry Creek.

To date, re-colonization of this habitat by native plant species has not occurred, and re-invasion of these habitats by weedy species occurs frequently . Ivy frequently returns to sites from which it was removed, usually as a result of incomplete removal of root biomass. The SCRP has recently increased its native plant output in an attempt to reintroduce native species to the banks of Strawberry Creek; the Program’s interest in discovering which native plant species will do best in this urbanized ecosystem guides this research. Volunteers with the SCRP helped clear nonnatives and plant native species at all of the sites mentioned below.Nine functional traits were measured on 38 plant species native to Alameda County, following from the methods in Cornelissen et al. . The regional species pool was narrowed to 38 species through a variety of considerations, most notably through the elimination of native species for which I did not have access to propagule material or species that did not grow well in the SCRP’s on-campus nursery . The 38 species were almost entirely understory species, a function of the SCRP’s focus on understory management. Species were selected from a variety of different habitat types to minimize the possibility of ‘pre-selecting’ species assumed to do well at Strawberry Creek. In addition to the native species, functional traits were measured on two non-native species: canary and English ivy. These species were included to discern the relative differences in traits between the native and nonnative species, an important prediction of limiting similarity. Ages and propagation methods were standardized across functional groups, to the extent practicable ; the SCRP’s long-standing nursery program had some gaps in records, making it difficult to determine the exact age or geographic origin of some individuals.The selected traits relate to diverse aspects of species morphology . When possible, ratios were used instead of raw values to minimize the effect of any age differences. All trait measurements were taken on plants grown in nursery settings . Trait measurements were taken on five replicate individuals for each plant species, cannabis dry racks then averaged across the replicates. The five replicates were spaced across five blocks in the nursery and species position within each block was randomized to minimize neighbor effects or the effects of divergent growing conditions.Plant nitrogen uptake is a focal point of this research, but was treated differently from the traits listed above. I aimed to discover how nitrogen uptake rates vary across species of different growth forms and geographic origins . A nitrogen-15 stable isotope tracer analysis was conducted to address these questions. For this analysis, five species representing four functional groups were given 15N-labeled ammonium chloride injections . These species were also included in the broader trait-based filtering study. Individuals used for the nitrogen uptake analysis were all of the same age and were all sourced from the Strawberry Creek watershed.

Our interest in controlling these factors, in addition to cost constraints, motivated the choice to evaluate nitrogen uptake only on representative species from each functional group, rather than test all species. As above, propagation methods were standardized within functional groups. In addition to four native species, the nitrogen uptake rate of canary ivy was also analyzed,to allow for the comparison of native and non-native uptake rates. Five replicate individuals of each species were given 15N injections. This work follows from James & Richards in terms of quantity of nitrogen delivered to the system. I assumed that in an urban setting, nitrogen will most likely be delivered to the riparian corridor in ‘pulse’ events carrying large amounts of nitrogen, e.g. rainstorms. However, I modified the methods in James & Richards to adjust for the size of the SCRP’s planting containers and different percent enrichment of 15N. In total, I added 2 mg of 15N in a 176.7 mL solution with de-ionized water to each plant. The solution was delivered via 18 injections in a circle around the base of the plant,to a depth of 10 cm.I attempted to label all parts of the soil column uniformly, injecting the solution into the soil at a slow and steady pace as I moved the syringe up through the soil column . The plants were harvested 13 days after injection.I chose to wait for a relatively long period of time between injection and harvest because this analysis was carried out in the non-growing season . The decision to perform the injections in the winter was pragmatic, based on this project’s timeline. Plants were kept dry for the week prior to injection and were not watered for the 13 days following injection. After the 13 days had passed, the plants were harvested and all plant biomass was dried and weighed. Leaf samples and root samples were collected for each plant; each sample was then ground and homogenized. Roots and leaves remained separate throughout this process. Approximately 5.5 mg of each sample was then weighed into tin capsules, yielding 50 samples: 5 species x 5 replicates x 2 samples/individual. These samples were combusted in an elemental analyzer, and isotopic ratios were analyzed by a mass spectrometer, yielding leaf and root 15N content for each individual plant.The California rice [Oryza sativa L.] growing region comprises approximately 200 000 ha in the Sacramento Valley. The region, which is among the highest-yielding in the world for rice production , is characterized by hot, dry, summers with abundant sunshine, and supports a single crop per year . The rice cropping system is almost exclusively water-seeded, wherein pre-germinated seed is sown by aircraft into flooded fields. Seeds sink to the soil surface and peg down roots, emerging from the water after several days. Floodwaters are generally kept to 10 to 20 cm depth for the entire season. Water seeding was widely adopted in the region in the 1920s as a means to suppress competitive grass weeds , and has been the predominant method of rice cultivation in California ever since . Continuous use of water seeding has resulted in a small spectrum of weed species that are well-adapted to the system, and are very competitive with rice . California rice has a limited number of available herbicides, due to the high cost of development and registration , as well as strict regulations based on concerns of herbicide drift from aerial applications that may damage neighboring orchards . Herbicide resistance has been a major biologic and economic issue in rice for decades . The lack of diversity of registered active ingredients means that once resistance to a particular mode of action arises, it can spread rapidly within and among fields as there may be few alternative herbicides to control the resistant populations. Efforts to promote herbicide resistance mitigation in CA largely focus on rotation of the limited number of available herbicides, while the cropping strategy itself has remained largely static.Most cultural methods for weed and resistance management in California are modifications of the dominant water seeded system . One such method used by some growers is a stale seedbed. In this method, rice seedbeds are prepared as usual and flushed with water to promote weed germination. Non-selective herbicides are used as a burndown treatment , and afterward the fields are flooded and seeded as usual. This method can be a useful strategy to manage weeds that are resistant to rice herbicides, as well as reduce weed seedbanks overall. However, due to the time needed to reflood and seed fields, stale seedbed use can delay rice planting, shortening the growing season and potentially depressing yields .

This one application will provide 4 to 6 years of adequate sulfur nutrition to the new pasture plants. Visible symptoms of sulfur deficiency include stunting and yellow color, although these symptoms also commonly indicate nitrogen deficiency. If you suspect sulfur deficiency after pasture establishment, cut the top 4 to 6 inches off of leaves at early bloom and submit a plant tissue sample to a lab for analysis. If grass tissue results indicate a sulfur level of less than 0.10 to 0.15 percent, you may have a sulfur deficiency. Common solutions are broadcast applications of soluble sulfur fertilizers such as ammonium sulfate or gypsum.The overriding characteristic common to newly established, dryland plant species is their low seedling vigor and slow growth and maturation. Typically, dryland perennial seedlings are so slow to get started that even several months after seedling their slim, vertical stalks are difficult to see. Since perennial seedlings mature slowly and are particularly susceptible to stress, a grower may not consider the stand to be “established” until it is 3 years old. Potential causes of pasture damage or loss may include lack of moisture and consumption by any number of animals, including cattle, deer, rabbits, ground squirrels, mice, and insects such as grasshoppers. Proper timing of cultural practices, seedling methods, and weed control help improve soil moisture conditions, cannabis drying racks but grazing must be light and controlled during pasture establishment to avoid excessive seedling losses.

Try not to allow grazing in the year of establishment, at least until the seedlings have completed their growth for the first growing season. Timingwill vary depending on elevation and site conditions, but this usually means no grazing before July 1. Under favorable growing conditions, the seeded plants will have developed numerous leaves and produced a seed head. After the plants produce a seedhead and go dormant , livestock can graze them down to 3 to 4 inches in height. If growing conditions are poor and the plants do not produce a seedhead, do not allow grazing at all. Regardless of growing conditions, many people merely plan not to graze a newly established pasture in its first year, just to be on the safe side. Proper grazing management is hard to determine during that first year. Often, the greatest benefit to the pasture from grazing is that grazing animals remove weeds such as annual mustards and grasses. Consider any grazing during the first year to be a prescribed clean-up operation rather than an extensive feeding on perennial seedlings. The key is to avoid grazing either too early in the summer, too close to the ground, or in muddy conditions. Grazing in late fall or winter should be avoided if muddy conditions exist, since the pasture will have developed very little sod by then to stabilize the soil and prevent soil compaction or erosion. Although livestock grazing can be controlled during seedling establishment, it is often impossible to control grazing by wildlife. Small plantings usually are the most susceptible to wildlife damage since it only takes a few animals to completely defoliate a small stand. In areas with large numbers of deer, rabbits, ground squirrels, or elk, you can seed areas of five or more acres at a time to reduce the chance of a complete loss of stand from wildlife grazing, although some areas of your planting may still be severely damaged.

Along with wildlife, insects such as grasshoppers, Mormon crickets, and black grass bugs can cause significant damage to new seedlings. During a year with high insect populations, you may have to apply some sort of control. In most cases, insecticides provide the best control for insects feeding on new seedlings, since a large insect population can destroy a stand in a matter of a few days. You will have to choose the most appropriate insecticide to use based on the particular insect pest and local site conditions, so you will do best to consult an agricultural specialist in the area before you apply a treatment. The second season after seedling, your management efforts should still focus on pasture stand establishment and you should continue to follow similar grazing guidelines to those you used the first year. Try to delay grazing until the plants have had the opportunity to complete their full growth for the season. Once drought conditions and cool temperatures have forced the plants into dormancy, graze them to a height of 3 to 4 inches and avoid grazing in muddy conditions. If growing conditions are favorable during the first two years, plants generally are well established by the third spring and you can proceed to manage the field as an established perennial grass pasture. If the first two years are marked by drought conditions, allow a third year of restricted grazing. This timeline is most applicable to introduced species such as crested or intermediate wheat grasses that have good seedling vigor and grazing tolerance. Native species that grow slowly and are sensitive to grazing may need three to five years to become completely established.Be cautious and conservative when you manage livestock grazing on dryland pasture, since desirable, dryland plants are quick to be degraded and slow to recover.

Do not start a problem that may persist for years, just in order to get a little extra grazing in one year. Be especially careful when you graze livestock during drought cycles that persist beyond a single growing season. Under severe conditions, improper grazing can lead to the loss of desired plant species, which will then be replaced by weeds. Weeds make pasture rejuvenation difficult and often lead to permanent changes in vegetation. Historical practice indicates that the best approach is to vary the season of use and to leave half of the forage growth ungrazed. For example, forage used in the spring this year should be grazed later in the growing season next year. This provides a long period of uninterrupted growth during which the plants can replenish their root reserves. When grazing in late spring and early summer, leaving half of the current year’s growth is a conservative practice that preserves the plants’ energy reserves in their roots and stems. If grazing is delayed until late summer or fall, pastures can be grazed down to a 3- to 4-inch stubble height without causing harm. In practice, these recommendations are best suited to producers who have enough pastures to permit a rotation that grazes some fields early one year and late the next year.But if you only have a single pasture to work with, vertical growing weed it is best to defer grazing until early summer in order to prevent weed invasion and allow the plants to recover their energy reserves. If the area receives ample precipitation, a single-unit pasture can occasionally be grazed in early spring, but always make sure to leave half of the current year’s growth and stop the grazing before soil moisture is depleted. When wheat grass pastures are grazed in early summer, it may be possible to graze them again lightly in the fall or early winter. If you do allow fall or early winter grazing, begin after the onset of winter dormancy and stop before the initiation of spring growth . Depending on what type of livestock are grazing, you may need to supplement their feed with hay in order to provide adequate nutrition during fall and winter grazing periods. Early spring grazing usually is not appropriate for degraded ranges or areas that are susceptible to invasion by annual weeds. In field trials conducted on Siskiyou County pastures that had high annual weed pressure, early spring grazing resulted in a more extensive invasion of undesirable annuals than in pastures subjected to late spring or summer grazing . This research suggest that canopy removal in early spring allows greater exposure to sunlight and seed-to-soil contact to encourage the establishment of annual weeds that out-compete later maturing perennials. For this reason, it is probably best to avoid early spring grazing.

Even if you do not graze your pastures, you sometimes have to remove plant cover using non-grazing management practices to prevent insect and disease problems and fire hazard concerns. The decision whether to mow or burn depends on how you want the pasture to look as well as several site characteristics. If unmanaged, perennial grasses create large amounts of dry, dead grass , posing a fire hazard. You can leave some plant material intact to help prevent invasion by non-native annuals and weeds, but if you leave too much it can lead to insect and fire problems. When practical, try to mow and bale excess forage and so reduce the accumulation of thatch and accelerate its decomposition. The best time to mow is after perennial grasses produce seed. You may also want to use controlled burning to remove accumulated thatch. Burning is a risky endeavor, though, and must be coordinated with the local fire department or the California Department of Forestry and Fire Protection . The best time to burn is after completion of perennial grass growth, but the exact timing of the burn depends on permit restrictions as well as site characteristics and other vegetation growing on the site. The influence of soil properties on herbicide efficacy has been widely studied as well as the influence of spray water quality on herbicide performance. However, limited studies on the effects of irrigation water quality on herbicide dissipation have been completed. This study was conducted to evaluate the effects of water pH and salinity on the dissipation of saflufenacil, indaziflam, and penoxsulam in two representative California orchard soils.The experimental protocol is a modified version of the method published by Sheppard et al.. The experiment was a completely randomized design with each herbicide being tested in both soil types at every water treatment and replicated three times. The amount of soil used in this experiment was determined by the bulk density of the soil and the assumption of a 25 cm2 spray area and a 2 mm soil depth. Each loam experimental unit contained 5.4 g of soil and each sand replicate contained 6.1 g of soil. Soil was first treated with herbicide by weighing appropriate amounts of each soil into a weigh boat, pipetting 1 mL of herbicide solution onto the soil, homogenizing by vigorousmixing, then letting the mixture sit for 24 hours until completely dry. The treated soil was then transferred into a 50 mL centrifuge tube equipped with a 0.22 µm Nylon filter . Soil was brought to field capacity by adding 1.220 mL of water treatment to loam soil or 0.780 mL of water treatment to sand soil, covered with parafilm, and left in the dark, at room temperature for seven days. After the resting period, the parafilm was removed and the samples were centrifuged at 6000 m s-1 for 15 minutes using a Sorvall Legend XTR centrifuge . After the initial centrifugation, an additional 1 mL of the respective water treatment was added to each sample then samples were centrifuged again at 6000 m s-1 for 15 minutes. This process was repeated once more for a total of two 1 mL water treatment aliquots washed over every sample after the field capacity water was removed. A separate pilot study completed to establish the number of water treatment washes needed to remove the unbound herbicide from the sample indicated that two 1 mL washes was adequate for the purpose of the experiment . The centrifuge filter was removed and discarded while all water from initial incubation plus the two 1 mL aliquots were collected from the centrifuge tube and filtered using a 0.22 µm Nylon syringe filter. The filtered solution was collected in an HPLC vial and analyzed using high performance liquid chromatography .Analyses were performed with an Agilent C-18 Poroshell 120 column in an HPLC system equipped with a diode array detector. Mobile phase A consisted of ultrapure water and mobile phase B consisted of acetonitrile with 0.1% formic acid. Chromatography was accomplished using an isocratic elution of 60% mobile phase A and 40% mobile phase B. The method run time was 9 minutes. All samples were observed at 270, 268, and 205 nm which corresponded to the absorbance of saflufenacil, indaziflam, and penoxsulam, respectively. The approximate retention time of saflufenacil, indaziflam, and penoxsulam were 4.9, 2.5, and 2.6 minutes, respectively . Samples were background corrected and converted into units of percent removal from soil using 5-point calibration curves .

A popular species may have several desirable characteristics, but if it is not well-adapted to the site, there is little chance for successful establishment. Annual precipitation is the most common determining factor for which species will successfully establish and persist on a given site. Do not select a species that requires more annual precipitation than is typical for the site. Table 2 lists minimum recommended amounts of average annual precipitation for several common dryland species. Another important site factor affecting species selection is soil type. In the intermountain region, key soil attributes include texture, depth, and alkalinity. Table 2 shows which soil characteristics are suitable for each listed dryland species. You can get information on local soil characteristics from the Natural Resources Conservation Service soil survey in conjunction with on-site evaluations, either performed by you or with assistance from a farm advisor, hired consultant, or NRCS conservationist. You will find more information on important soil attributes in the Site Selection section.Seed prices and seed supplies vary from year-to-year depending on production and demand. Typically, native species are more expensive and in shorter supply than common introduced species such as intermediate or crested wheat grass. Seed cost can be a considerable factor on large projects, and it is not uncommon for a native seed mix to cost more than $100 per acre. Although seed can be expensive, vertical racking it is important that you not use less than the recommended seedling rate in order to meet a budget.

When considering costs, always remember that any dryland planting is at the mercy of the weather during the year of establishment. Dry spring weather is not unusual, so when it comes to the cost of seed, decide how much money you are willing to risk in that particular year and bear in mind that a repeat seedling may be necessary in future years.Introduced wheat grasses are the most commonly seeded species in the inter mountain region. They tolerate grazing well, adapt to many soil types, and have good seedling vigor, and the seed is almost always available in adequate supply and at a reasonable price. If you are looking for a reliable, affordable choice, choose the best-adapted wheat grass for your area. On sandy loam soils where precipitation averages 14 or more inches per year, intermediate wheat grass is usually the best choice. On drier sites, pubescent wheat grass is often preferred. Most wheat grass species can be mixed with drought tolerant forbs and shrubs. Table 3 presents some typical seed mixes that are based on introduced wheat grasses and used with the objective of improving livestock forage.There is a long-running debate over the benefits of planting introduced versus native plant species. In the early years of range improvement, introduced species were used almost exclusively for rangeland seedlings. Introduced species have several general advantages over their native counterparts in terms of seed cost, ease of establishment, and tolerance to grazing. For example, when native and introduced grasses were seeded in trials conducted in Siskiyou and Lassen Counties, introduced wheat grasses nearly always outperformed native grasses by a substantial margin with regard to seedling survival and establishment .

The advantages of high seedling vigor and ease of establishment are especially important on sites that are prone to invasion by noxious weeds such as cheat grass, medusahead, or yellow starthistle. Restoration ecologists continue to work on methods to improve seedling techniques for native species, but for now, introduced species have a significant advantage over native species with regard to establishment success.Proponents of native species point to the inherent benefits of maintaining species that are native to a given region, even though those species may be hard to establish. Native species proponents have two common concerns about planting introduced grasses: the lack of natural recruitment of native forbs and shrubs into stands of introduced grasses, which carries with it a reduction in plant diversity and possibly wildlife habitat; and the species’ potential to spread into, and possibly outcompete, nearby native plant communities. The competitive nature of a well-established stand of introduced wheat grasses may impede the establishment of some native species. However, there is no published research clearly demonstrating that grasses native to inter mountain rangelands are measurably more compatible with native shrubs and forbs than are introduced wheat grasses, nor have introduced wheat grasses been observed spreading into intact native plant communities. In actuality, there are many places within the inter mountain region where sagebrush, juniper, and other native species have moved into established wheat grass seedlings. In any case, it is clear that a well-established stand of perennial cool-season grasses is preferable to the weedy annual grasses or other noxious weeds that typically invade range sites where pasture seedlings fail.

Seeding recommendations vary from single grass species to complex seed mixes. Mixes are an attractive choice because they address variations in soil characteristics and provide a diversity of species that offer various benefits to livestock, wildlife, and the suppression of weeds. Managing a seed-mix planting can be quite complicated, however, especially when it comes to weed control and livestock management. On a relatively small homogenous site, a single grass species or a simple mix of a single grass and a forb is often adequate. Single-species plantings are easy to manage and can supply livestock with needed forage. Single-species pastures also allow managers to choose from a wide range of herbicides that they can safely apply for weed control. They also eliminate the potential for uneven livestock grazing based on the animals’ preference of one plant species over the other. Large seedlings that feature more variation in soils may warrant a more complex species mix. Subtle differences in soil and microclimate can be enough to favor one species over another, so by seedling a mixture of several species you can often improve the odds that at least a couple of species will establish over the entire landscape. Furthermore, by planting mixes you can improve biodiversity across the landscape. When deciding on which species to include in a seed mix, choose plants with similar levels of seedling vigor, maturity dates, tolerance to grazing, and palatability. A species mix that varies too widely in these characteristics will usually yield a field where grazing preferences can lead to overgrazing and loss of the most palatable species.Seeding rates vary depending on plant species, site conditions, and seedling methods. Table 2 provides recommended seedling rates for several dryland forage species, assuming optimal site and seedling conditions. When broadcasting seed onto rough or rocky terrain, rolling benches you may want to increase the seedling rate to help compensate for an unavoidable lack of uniformity in seed placement. If weeds are a problem, you can try increasing the seedling rate to improve weed suppression after grass establishment, but you will still need to control weeds throughout the establishment phase. Although increases in the seedling rate can be beneficial, they are no substitute for proper establishment practices. Excessively high seedling rates can even result in the failure of a stand. Soil moisture is a limiting factor, and a high seedling rate can lead to high seedling mortality as plants of the desired species compete with one another for that moisture. Actual seedling rates should be based on the Pure Live Seed Percentage . PLS is a computation that reflects the germination and purity of a seedlot where a PLS of 100 percent equals 100 percent germination and purity. Referring to PLS, you can accurately compare different seed prices and know that you are sowing at the correct seedling rate. To determine the PLS for a seedlot , you multiply the seed germination percentage by its purity percentage and then divide by 100. Germination and purity percentages are listed on the seed bag along with percentages of weed seed and inert matter. Avoid buying seed that contains noxious weeds or high levels of inert matter and aim for a PLS above 80 percent.

To convert the recommended PLS seedling rate to a bulk seedling rate, divide the PLS seedling rate by the seedlot’s PLS percentage and then multiply by 100.The fall seedling period runs from September to early November. Seeding at this time takes advantage of growth during the coolest, wettest time of year, when plant water needs are low. By seedling perennial grass at this time, you can give the plants a better opportunity to become established before moisture stress occurs. There are several risks and problems associated with seedling in both early and late fall, however. Early fall seedling. A dryland pasture crop seeded early in the fall can fail if there is sufficient rainfall for germination in early fall but it is followed by an extended dry period. The seed germinate with the initial rainfall, but can then desiccate and die if no subsequent rainfall comes soon enough. Late fall seedling. The chances of more continuous rainfall are greater for seedlings made later in the fall. When you seed late in the fall, however, temperatures may be so cold that plants cannot germinate or become well established before the onset of winter. On some soil types there is a risk of frost heaving of small seedlings as a result of winter freeze-and-thaw cycles. An additional problem with fall seedlings is that winter annual weeds, particularly grasses, generally emerge at the same time as the plants you have seeded. Winter annual weeds grow rapidly, often outcompeting perennial grass seedlings, and unfortunately there are few ways to control these weeds after crop emergence . Despite the risks and the potential for weed problems, fall may be the best time to seed a dryland pasture, especially in areas where the soil is too wet for planting in spring. Seeding in late fall also works best on alkali soils, where it allows seeds to take full advantage of the diluting effect of winter moisture and waterlogged soil conditions.Tillage may or may not be necessary for a dryland seedling, depending on soil conditions, what weeds are present, and what tillage equipment is available to you. Plowing or ripping to prepare a seedbed is common for most field and vegetable crops but rare for dryland seedling because the economic returns normally do not justify the cost of intensive tillage. In addition, the soil in many dryland pasture sites is too rocky or too shallow to allow any type of deep tillage. Disking or harrowing will usually suffice. This sort of less-intensive tillage serves to loosen the soil enough to let the planter place the seed at the proper depth and cover it with soil. Disking or harrowing also help control weeds that may have emerged before the time of planting. The biggest disadvantage of tillage involves soil moisture—especially for late winter to spring seedlings. Soils at this time of year are often too wet to allow any type of tillage operation. If you feel it is necessary to till before you plant, you have to delay your planting date until the soil has dried enough to allow tillage. This may delay planting beyond the most desirable period and soil moisture may become too scarce when the grasses are trying to get established. In addition, when you till a field it loses much of its soil moisture through evaporation. That means the crop will require rainfall after seedling just to allow the seeds to germinate and to settle the seedbed. One way to minimize soil moisture losses during spring tillage and seedling is to work one day at a time, tilling only the amount of land you can plant that same day. When you prepare a seedbed and plant it on the same day, you can plant the seeds directly into the soil moisture that tillage has brought to the surface. This strategy does have disadvantages, though: you have to pack the soil immediately after tillage in order to achieve a firm seedbed, and there is the hassle associated with switching every day between tillage and seedling activities. A firm seed bed is important: it keeps the seed from being planted too deep and provides good seed-to-soil contact, so if the seed drill is not equipped with press wheels you will want to use a cultipacker behind the drill. Extensive leveling is not usually necessary in dryland seedlings simply because the field will not be irrigated and problems with puddling or dry spots are not likely.

Original equipment manufacturers have identified an emerging market for BE MHDVs, advertising them to fleet operators as an opportunity to reduce operating and maintenance costs and their ecological footprint. While environmental benefits of BEVs are broadly appreciated, they can vary substantially depending on complex interactions between vehicle behavior , the physical environment , as well as characteristics of the electrical power grid used to charge these vehicles. Due to the nuanced complexities of freight truck electrification, the MHDV market has focused BEV deployment strategies to target specific vocations that have operational characteristics that are the most conducive to electrification. Local small parcel delivery vehicles have received the most attention, due to the relatively low daily miles travelled and lower loads and less strenuous duty-cycles that do not require larger battery capacity. Signaling the attractiveness of BEV deployments in parcel delivery vocations, the United States Postal Service awarded contracts for over nine thousand BEVs and over fourteen thousand charging stations in early 2023 in support of the agency’s stated goal to make 75% of its newly acquired vehicles electric, rising to 100% in 2026 and thereafter. The United Parcel Service has a similar goal of reaching 40% alternative fuel in the company’s ground operations by 2025 and carbon neutrality by 2050. UPS currently boasts over one thousand BEVs and PHEVs on the road in support of that goal and has agreements in place to purchase thousands more. Other vocations have also begun to reap the benefits of BE MHDVs in recent months as well. In late 2022, PepsiCo received the first order of Class 8 Tesla Semi electric trucks for deployment in their beverage delivery operation.

Frito-Lay, a PepsiCo subsidiary, deployed 40 electric vans within their North American division last year. PepsiCo’s Class 8 heavy-duty trucks will operate on short and regional haul duty cycles. While the electrification of long-haul heavy-duty semitrucks has been studied closely, grow rack the significantly greater trip lengths, payloads, and subsequent greater energy demands and fuel consumption, necessitate larger and more powerful batteries for HDV electric power trains than are provided by current technology in most cases. BEV models capable of long-haul operations are on the horizon, but existing BE MHDVs have operational ranges of less than 250 miles, with a few but growing number of exceptions. Policy levers orchestrated by local, state, and national governments have also helped to accelerate much of the recent growth observed in truck freight electrification. In 2021, the California Air Resources Board finalized their Advanced Clean Trucks rule, setting a standard requirement for 50% of new medium- and light heavy-duty vehicle and 30% of new heavy-duty tractor sales to be zero-emitting by 2030 as shown in Table 1. New York state adopted a similar rule, establishing a ratcheting standard for percentage of new electric MHDV sales as a share of total MHDV sales, culminating in 100% of new MHDVs registered in the state being zero-emitting by 2045. In addition, a coalition of 17 US states plus Washington D.C. and the province of Quebec, Canada signed a memorandum of understanding in 2022 committing to reaching 30% of new MHDV sales being zero-emitting by 2030, rising to 100% by 2050. This coalition estimates the potential net economic savings of the full electrification of the national MHDV fleet to be as much as $140 billion cumulatively, across the vehicles’ lifetimes.

At the Federal level, the United States Environmental Protection Agency announced a proposed rule that applies more ambitious pollution standards to heavy-duty vocational vehicles, and CARB projects that the new rule will avoid 1.8 billion metric tons of GHG emissions between 2027 and 2055, and provide significant particulate matter and other criteria pollutant emission reductions. According to the U.S. EPA, the industry can meet the new standards by achieving 50% zero-emissions vehicles for vocational vehicles, 34% for day use tractors, and 25% for sleeper cab tractors in MY2032, with a mix of BE and fuel cell technologies. The U.S. EPA also projects significant savings for electric MHDV purchasers due to reduced operating costs, despite increased upfront costs and after accounting for available battery tax credits. The regulatory focus on, and the consideration afforded to, electric trucks in present and future plans of players in the road freight industry signal an emerging alignment on the public and business benefits of electric MHDVs. There is widespread agreement in the freight industry that electrification can be a sound business choice, with operating mode savings surpassing higher MSRPs relatively early in the ZEV’s useful lifetime. In support of their rule making, the U.S. EPA found that most zero-emitting MHDV purchasers would offset their increased upfront costs, including the cost of electric vehicle supplementary equipment like charging infrastructure, with operational savings within three years of ownership. Elsewhere, Gao et al simulated energy consumption of a Class 7 local food delivery truck and found a battery electric or Power-GenSet PHEV can reduce the overall cost for energy by 29 to 44 percent, with the noted variability attributable to on-route charging availability, payload characteristics, and other factors. However, these authors did not consider the increased cost of electric power train technology. Another study assumed a MSRP differential of around $100,000 between a conventional Class 8 diesel and battery-electric semi-truck and found a baseline payback period for the BEV of 3.24 years ±1.46 years.

The reality remains, however, that the magnitude of savings and payback periods are heavily dependent upon each vehicle’s routes, on-road operating characteristics, and the design of the freight distribution system for each electrification application. A primary analytical goal of fleet electrification assessment is to identify what makes one use-case more attractive for BE technology deployment than another. This requires knowledge of the operational configurations of the fleet and availability of an analytical tool that can assess electrification benefits. A simple, standardized technoeconomic analytical framework can leverage preexisting economic and lifecycle models, while also reducing the modeling knowledge required to evaluate the electrification merits for specific conditions. The TCOST model is designed to help identify feasible use cases that can lead to the most efficient roll out of electrification within specific sectors/businesses in the MHDV fleet. The TCOST model implements an economic analysis framework that can be applied to any freight sectors wherein fleet composition, freight loads, and on-road activity can be quantified, and then calculates economic benefits and disbenefits of BEV deployment, as well as energy use and emission reduction benefits by applying existing energy use and air quality models within the economic analysis framework. As part of this research, an example short-range to-mid-range MHDV freight use-case is assessed using TCOST for the state of Georgia. The use-case example operating profiles presented in this report indicate how specific drayage freight flows can bring into focus the characteristics that help or hinder electrification potential. The Total Cost of Ownership Spreadsheet Tool is provided as a Microsoft Excel®-based model , distilling the framework utilized in the use case evaluation down to a simple user interface with a series of inputs to customize calculations for user-defined use-cases. TCOST integrates primary data, functions, and assumptions of MOVES-Matrix for “Pump-to-Wheels” energy consumption and emissions rates, and the DOE GREET model energy consumption while also incorporating from the literature, additional information relevant to the simulations. TCOST expedites the analytical process and vastly reduces required modeling knowledge for MHDV electrification analyses, vertical racks removing knowledge barriers and facilitating more efficient and effective decision-making for freight brokers and MHDV fleet managers. Finally, TCOST is applied to the previously defined use-case to demonstrate its utility for fleet managers and planners as a simplified method for back-of-envelope calculations using a handful of user inputs to assess benefits and inform decision-making. The TCOST application to the use-case serves as an instructional model for future use of the tool.Understanding the form, trends, and operational conditions of Georgia’s freight system is important because it provides a context against which individual vocations can be evaluated. Handling over 850 million tons of freight flows annually, the state of Georgia boasts one of the most robust freight networks in the United States. The state is home to the nation’s most significant airport for air cargo with Hartfield-Jackson International , the fastest growing container port with the Port of Savannah , and the southeast hub of operations for two Class I railroads in the eastern U.S. with Norfolk Southern and CSX.

Georgia’s Interstate system is in the top ten among states for interstate miles , and Georgia has an extensive network of state highways and local roads providing enhanced connectivity. The state’s logistic industry is a critical component of the state economy; in 2018 logistics was responsible for about 7% of Georgia’s GDP and nearly 500 thousand jobs, including 239 thousand direct jobs. In Georgia, 75% of total 2018 freight flows by weight are carried by truck, with almost the entire remaining 25% of total tonnage carried by rail. An even larger share of freight value was carried by truck. Truck freight is uniquely positioned to provide door-to-door service between almost any origin and destination, enabling highly flexible delivery scheduling at low cost and on short notice. For this reason, truck mode share and total volume in Georgia are forecasted to grow substantially, in line with the growth of same-day or next-day deliveries associated with e-commerce. Truck freight flows in Georgia are expected to grow anywhere from 1.5% per year to 2.2% per year and Economy.com estimates through mid-century [19].Georgia’s truck freight system activity is geospatially centered around the Metro Atlanta region as well as the Port of Savannah. Atlanta is the second largest population center in the southeast U.S. and is a major manufacturing and commercial hub. The Port of Savannah is the second busiest container port in terms of total throughput on the East Coast. Figure 1 shows the convergence of multiple significant freight corridors in Georgia’s Atlanta region for both interstate and intrastate commodity flows. Figure 2 is from the Atlanta Regional Commission’s latest regional freight mobility plan published in 2016 and depicts truck volumes on the Interstate system and state highways in the Atlanta region. The dense truck traffic on the I-285 perimeter is primarily due to interactions between through truck movements generated outside of the metro area with destinations also outside of the region , coupled with local delivery trucks transporting goods between warehouses and distribution centers and to locations within the region. The top twelve truck count locations in Georgia are in the Atlanta metropolitan region. The restriction of activities on I-75 and I-85 inside the I-285 perimeter lead to comparatively low truck counts on those thoroughfares. The Atlanta-Savannah corridor is especially significant to the economic well being of Georgia as it connects the state’s regional economic and population center with the Southeast’s primary link to the international market at the Port of Savannah. Over 100 thousand loaded trucks complete trips between Atlanta and Savannah every year , and three intermodal trains also depart every day. These numbers have only grown since the Georgia Ports Authority completed a deepening project in Savannah harbor in 2022, which is estimated to allow a typical container ship to load an additional one thousand containers and increase import and export volumes at the Port of Savannah.The Georgia Ports Authority owns and operates inland ports of their own. Appalachian Regional Port in northwest Georgia is operated in public-private partnership with CSX. ARP has direct CSX railway connection to the Port of Savannah and easy access to the I-75 corridor, providing inland intermodal transfers about 100 miles from both Atlanta and Knoxville, TN and 45 miles from Chattanooga, TN. GPA bench marked the capacity of ARP at 50 thousand containers per year when it opened in 2018 and there are plans to double its capacity by 2028. GPA estimates each round-trip container moved by rail to and from ARP to offset 710 truck miles on Georgia’s highways and the port diverts up to 40 thousand trucks from Atlanta area roadways each year. Bainbridge Terminal in southwest Georgia primarily handles intermodal transfers for containers traveling by barge on the Apalachicola Chattahoochee-Flint waterway system in that part of the state. Construction plans for another inland port facility in Hall County, northeast of the Atlanta region, gained federal environmental approval in May 2023. GPA estimates construction to be completed in 2026.