Response of four spring-seeded cover crops to residues of selected herbicides

Abstract

Yu, L., Van Eerd, L. L., O'Halloran, I., Sikkema, P. H. and Robinson, D. E. 2015. Response of four spring-seeded cover crops to residues of selected herbicides. Can. J. Plant Sci. 95: 303–313. Although herbicide labels provide crop rotation restrictions, information is limited on the influence of herbicide residues on cover crops. Field experiments were conducted in 2011/2012 and 2012/2013 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and growth of buckwheat (Fagopyrum esculentum Moench), annual ryegrass (Lolium multiflorum Lam.), sorghum sudangrass [Sorghum bicolor (L.) Moench×Sorghum sudanense (P.) Stapf], and spring wheat (Triticum aestivum L.) spring-seeded cover crops planted 1 yr after application. Imazethapyr (100 and 200 g ha−1) was applied pre-emergence (PRE) to processing peas (Pisum sativum L.), while S-metolachlor/atrazine plus mesotrione (2880+140 and 5760+280 g ha−1) and saflufenacil/dimethenamid-P (735 and 1470 g ha−1) were applied PRE to sweet corn (Zea mays L.). Imazethapyr residues from 200 g ha−1 caused 75 and 48% visible injury in buckwheat and sorghum sudangrass, respectively. Plant light attenuation, shoot dry weight, and nitrate-nitrogen content were reduced up to 82, 64 and 67% in buckwheat, and 40, 11 and 24% in sorghum sudangrass, respectively, by residues from imazethapyr. S-metolachlor/atrazine plus mesotrione residues caused up to 53% visible injury to annual ryegrass and reduced plant light attenuation, shoot dry weight, and nitrate-nitrogen content by as much as 59, 48, and 55%, respectively. There were no observable adverse effects of visible injury, light attenuation, shoot dry weight, and nitrate-nitrogen content on spring wheat regardless of herbicide or rate. These results indicate that buckwheat and sorghum sudangrass should not be grown in the year following imazethapyr, and that annual ryegrass should not be grown in the year after application of S-metolachlor/atrazine plus mesotrione. However, no restrictions are needed for growing spring wheat following these herbicides.