In wheat growing regions of the Intermountain West, Kochia scoparia (kochia) is a major invasive pest that can significantly reduce yields. Alternative techniques, such as employing agroecological practices, are needed to address kochia and many other problem weeds that are becoming resistant to traditional chemical management. Agroecology incorporates many of the processes associated with natural succession in the management of crops. These tactics, however, are rarely employed in the semi-arid Intermountain West, mainly over concerns on water demands. However, the use of these techniques that maximize competition in the suppression of weeds have often been employed elsewhere with varying levels of success. Therefore, a two-year field study was conducted to determine crop planting date and seeding rate, and cover crop effects on the suppression of kochia and other problem weeds in irrigated wheat production systems in Utah. Spring wheat was planted on two planting dates (early and late spring) and at two seeding rates (100 lbs/A and 150 lbs/A) along with a cover crop (Trifolium pratense ‘dynamite’ red clover) and a combination cover crop and low efficacy herbicide management treatments. For comparison, a standard herbicide and untreated control were included as management treatments in the study. During the growing season, quadrat samples were used to measure cover and transect counts were used to estimate wheat stands. Collection of plant shoot growth for biomass at the end of the season was done using quadrat samples. Total plot yield data was collected at the time of wheat harvest as well.
Results/Conclusions
Preliminary findings indicate that crop planting date and weed control method significantly influenced weed biomass at harvest (p=0.00051, p=4.37e-08) and control method continued to influence weed biomass after crop harvest (p=1.834e-11). Wheat stand was negatively influenced only by planting date and rate (p=<2e-16, p=0.012) and grain yield by year and planting date (p=0.0415, p=0.0002), but not by the control method. Our results show that cover crops have no competitive effect on wheat yield, while effectively suppressing weeds, including kochia. By planting earlier in the season the crop is provided a competitive advantage over undesired plants. Through using cover crops thereby increasing the diversity and population size of the system, the increased competition better allows for exclusion or suppression of weeds, including kochia. Agroecological approaches can be used to successfully manage weeds in cropping systems, while increasing diversity and supporting ecological plant and soil relationships.