VEGETATION MANAGEMENT AND INTERRILL EROSION IN NO-TILL CORN FOLLOWINGALFALFA

No-till corn (Zea mays L.) following alfalfa (Medicago sativa L.) is r ecommended for reducing soil erosion; however, killing alfalfa in the fall may result in insufficient crop residue cover for Conservation Co mpliance soil erosion goals. We hypothesized that soil conservation ef fectiveness was related to burn-down spray date and final harvest date influence on cover. A Wisconsin held study to test this hypothesis in cluded fall and spring burn-down spray dates in combination with eithe r August or September final alfalfa harvests. Soils included Piano and Saybrook silt loams (fine-silty, mixed, mesic Typic Argiudolls) on 2 to 9% slopes and Palsgrove silt loam (fine-silty, mixed, mesic Typic H apludalf) and Reedsburg silt loam (fine-silty, mixed, mesic Aquic Pale udalf) on 7 to 14% slopes. Simulated rainfall (72 mm h(-1) for 1 h) wa s applied following corn planting. The fall spray-September harvest QS -SH) averaged 25% residue cover, measured after planting, with soil lo ss of 257 g m(-2). The spring spray-August harvest (SS-AH) averaged 79 % residue cover and 24 g m(-2) soil loss. Of the 72 mm of rain applied on each of the treatments, 34 mm ran off the two FS treatments, 23 mm ran off the SS-SH treatments, and 19 mm ran off the SS-AH treatments. Treatment runoff amounts and final infiltration rates related in part to surface macroporosity and surface sealing. Fall herbicide applicat ion resulted in too little residue cover to adequately reduce soil ero sion.