Safflower seedlings remain in the rosette stage for 3 to 4 weeks after emergence and the canopy closure occurs late in the season; hence, early-emerging weeds species can easily outgrow and shade the crop . Trifluralin, EPTC, ethalfluralin, and S-metolachlor are the preemergence /preplant incorporated herbicides labeled for use in safflower. Trifluralin was the first herbicide labeled for use in safflower . It is effective on some annual grasses, but does not adequately control Brassica species,kochia, and Russian-thistle. These weed species are particularly troublesome in safflower production areas of this region, including Montana .Furthermore, the need for soil-incorporation of trifluralin, ethalfluranlin, andEPTC for optimum weed control often limits their use in no-tillage semi-arid cropping systems of this region. Smetolachlor applied PRE controls annual grasses and few broadleaf weeds such as pigweeds .During 1980s, sulfonylurea herbicides such as chlorsulfuron, metsulfuron,and thiameturon were tested, particularly for post emergence broadleaf weed control, in safflower.
Previous studies found that safflower exhibits variable tolerance to these SU herbicides, and moderate to severe injury may occur if applied to safflower plants less than 15-cm tall.This is a major limitation in using these SU herbicides for early-season POST weed control, cannabis grow tray especially for weeds such as kochia and Russian-thistle, which can emerge very early in the spring before or with safflower seedlings in the US Great Plains. Thifensulfuron is the only POST herbicide currently labeled for broad leaf weed control in safflower in the US . However, the widespread occurrence of ALS-resistant kochia and Russian-thistle in Montana and several other states in the US Great Plain srenders thifensulfuron in effective for controlling these weed biotypes in safflower.Therefore, there is a need to investigate alternative herbicide programs for improved broadleaf weed control in safflower, especially kochia and Russian-thistle, and to facilitate registration of new products for use in safflower.The objective of this research was to investigate effective PRE soil-residual herbicide programs for improved crop safety and season-long broad leaf weed control in safflower.
All data were subjected to ANOVA using the MIXED procedure in SAS 9.3 . Data on crop injury and weed control were arcsine-transformed and weed density data were square-root-transformed before analysis to improve homogeneity of variances and normality of residuals. Non transformed means are presented in tables based on the interpretations from the transformed data. Year, herbicide treatment, and their interactions were fixed effects, and replication and interactions involving this variable were random effects in the model. Data were pooled across locations whenever year by herbicide treatment interaction was not significant. Means were separated using Fisher’s protected LSD test at P < 0.05. The 2016 growing season was slightly wetter compared to the 2015 growing season. However, the treatment by year interaction was not significant on safflower visual injury, weed density, percent weed control, or safflower grain yield; therefore, data were pooled over years. Organic rice has started to gain popularity as the safer and healthier alternative,especially in developed countries .
Demand for organic rice is increasing with up to 50,000 acres produced in the USA . In US, organic rice farmland has increased almost six times since 1995 to now . However, current organic rice production in US is unable to meet the current market demand. Organic rice buyers in the US are importing large percentages of their rice from Cambodia.Major challenges in organic rice production include nutrient optimization,weed management and variety selection . Weed competition is one of the prime yield limiting biotic constraints in rice . Uncontrolled weed can reduce rice yield by 44% to 94% . Weeds even can cause total crop failure .Through selection of weed competitive cultivars, the weed emergence and its subsequent growth can be suppressed . Thus, varietal selection can be alternative to weed management in organic rice. Likewise, flooding and cover cropping are tools in integrated weed management for organic rice production.