INTERROW CULTIVATION TO REDUCE HERBICIDE USE IN CORN FOLLOWING ALFALFA WITHOUT TILLAGE

Information on integrated weed management systems for conservation til lage systems is needed so that producers can minimize the environmenta l impacts of crop production without sacrificing profitability. Our ob jective was to evaluate reduced levels of reemergence herbicides in co mbination with interrow cultivation for weed control in corn (Zea mays L.) planted into an untilled, deteriorated alfalfa stand treated with glyphosate [N-(phosphonomethyl)glycine] the previous fall. Fall appli cation of glyphosate controlled 97% of the perennial vegetation withou t additional treatment the following spring. Atrazine hyl-N'-(1-methyl ethyl)-1,3,5-triazine-2,4-diamine] at 1.1 kg a.i. ha-1 or cyanazine (2 -[[4-chloro-6-(ethylamino)1, 3,5-triazin-2-yl]amino]-2-methylpropaneni trile) at 2.2 kg a.i. ha-1 applied within 1 d after corn planting grea tly reduced weed densities compared with no herbicide use, but did not control annual weeds as well as a standard treatment (atrazine at 2.2 kg ha-1 plus 2.8 kg a.i. ha-1 metolachlor hylphenyl)-N-(2-methoxy-1-m ethylethyl)acetamide]). In most cases, one or two interrow cultivation s following atrazine or cyanazine increased control of annual weeds to > 90%, which was similar to the standard treatment. Corn grain yields were affected by varying environmental conditions during the three ye ars of research, but in the two years without drought, integrating cul tivation and reduced levels of herbicide resulted in corn yields equal to the standard herbicide treatment. This research indicates that int egrating interrow cultivation with reduced levels of herbicide is a so und weed management option for corn planted into untilled, fall-contro lled alfalfa stands infested with perennial weeds.