Evaluating weed management decisions that influence cover crop adoption in the Upper Midwest

Abstract

The use of pre-emergence residual herbicides has proven to be an effective strategy for controlling problematic late-emerging weed species in annual crops. However, the use of residual preemergence (PRE) herbicides has the potential to negatively affect other crops within an annual two-crop rotation, such as fall-planted cover crops. The intent of this study was to determine if residual PRE herbicides would affect the emergence and growth of fall-planted cover crops. Four PRE herbicides, dimethenamid-p, a packaged mixture of dimethenamid-p + saflufenacil, a packaged mixture of acetochlor + clopyralid + mesotrione, and a layered treatment of dimethenamid-p 30 days after first application of dimethenamid-p were applied before silage corn planting. Following silage corn harvest in the fall, three cover crops, winter cereal rye (S. cereale ), winter camelina (C. sativa ), and red clover (T. pratense) were planted with a no-till drill at three locations in Minnesota that differed in soil type and climate. Plant measurements were obtained for each cover crop at burndown in the spring to assess establishment, growth and biomass. Cover crop height, plant density, and ground coverage in the spring were influenced by an interactions between cover crop species, herbicide, and location . However, there was no difference in the total biomass accumulation at termination the following Spring. These results indicate that application of these residual PRE herbicides for control of late-emerging weed species did not interfere with cover crop biomass production as long as soil moisture was at or above normal during the growing season.