Although selection and/or identification of allelopathic plants from medicinals plants are much easier than other group of plants, isolation and identification of strong allelopathic substance is laborious, time consuming and need very sophisticated equipment’s. Hence, to date very few works have been conducted to isolate and characterize the allelopathic substances from allelopathic medicinal plants. A list of allelopathic substances isolated from different medicinal plants is given in Table 2. These substances showed strong phytotoxic potential against different target plant species under laboratory condition. However, their phytotoxic potential under field condition not yet reported. It is well known that even a substance showing strong phytotoxic activity on target plants in laboratory experiments, may not perform satisfactorily in the field conditions due to the influence of several soil factors like soil pH, organic carbon, organic matter and available nitrogen. Therefore, more emphasis should be given on evaluating the bio-activity of allelopathic substances or the allelopathic plant extracts in both laboratory and field condition.
If the extracts or the isolated compound shows strong activity in both conditions only then it could be recommend for new natural herbicide development. is a recently registered sulfonylurea herbicide for broad leaved weed control in white bean in Ontario . Therefore,cannabis grow equipment halosulfuron needs to be used along with a graminicide to provide broad spectrum control of problematic weeds in white bean.S-metolachloris a chloroacetanilide herbicide that is registered in white bean to control of key weeds in Ontario including Echinochloa spp., Setaria spp., Panicum spp., Digitaria spp., Solanum spp.and Amaranthus spp. .S-metolachlor tank mixed with halosulfuron cancontrol troublesome grass and broad leaved weeds in white bean.The S-metolachlor label has a dose range of 1050 to 1600 g∙ai∙ha−1 and the halosulfuron label has a dose range of 25 to 50 g∙ai∙ha−1. Earlier research has primarily focused on halosulfuron at 35 g∙ai∙ha−1 for weed control in white bean. Limited information exists on the effect of Smetolachlor plus lower doses of halosulfuron particularly at the lowest labelled dose of 25 g∙ai∙ha−1 for weed control in white bean.
Studies are needed to determine the appropriate application dose of halosulfuron alone or in tank mix with S-metolachlor for broad and comprehensive weed control in white bean. This information will allow producers to reduce their input costs and minimize crop losses from weed interference in white bean.The purpose of this research was to evaluate how doses of S-metolachlor and halosulfuron should be adjusted to control specific problematic weeds in white bean production.Agricultural practices have caused major changes in the composition and species richness of weed communities in the field.Arable weed species play an important role in supporting biological diversity in agro- ecosystems . Weed species that thrive in the field edges and may colonize cropped plots include Avena sterilis and Galium aparine , Conyza canadensisand Senecio vulgaris . In other studies, plant populations in field edges have not resulted in weed infestations in the adjacent crop in many studies.There is evidence that herbicide efficacy, increased crop competition and changes in cropping patterns have resulted in a gradual decline in weed abundance and diversity over recent decades.Herbicide use is a widespread practice detrimental to weeds and continued use of a single herbicide often results in weed composition shifts from highly susceptible species to those having greater tolerance to the herbicide . The most used herbicide in arable crops in Argentina is glyphosate which provides application flexibility, lacks of rotational restrictions and controls a broad spectrum of weeds.However, as a result of repeated use, species difficult to control with glyphosate have become more common in many countries and in Argentina as well.
Weed diversity may be concentrated in the crop edges, especially in the weed communities of conventional cereal fields . In Argentina, crop edges are narrow areas that are taken out from agriculture. In crop edges, insecticides, fungicides are not used and occasionaly, herbicides are applied. In the field plot, the most used herbicide is glyphosate-alone or in combination with residual herbicides . The objective of this study was to analyze weed abundance and diversity as well as the frequency of weeds tolerant or resistant to glyphosate in field plots and edges in the soybean central region of Argentina. Overall, MRPP indicated variations in species composition between edges and field crops. Two weed communities were identified according to season: Spring-summer and winter.Variations in weed species composition between seasons were also observed in another study .