Maize Residue Removal and Cover Crop Effects on Subsequent Soybean Crops.

Residue removal and cover crop treatments often differentially affect cash crop yield across geographical regions. Objectives were to examine maize residue removal and cover crop treatment effects on soybean grain yield and seed components (moisture at harvest and mineral nutrients) near Brookings, SD. A field study consisting of three maize residue removal treatments superimposed on a 2-yr maize-soybean rotation was established in 2000 under no-till soil management. Maize residue removal treatments [designated LRR (low residue removal; grain harvest only), MRR (medium residue removal; stalks chopped after grain harvest, windrowed, and removed), and HRR (high residue removal; cutting stalks and removing fodder as silage)] were main plot treatments. Sub-plot treatments were the absence or presence of cover crops (fall planted slender wheat grass in corn and hairy vetch/oats in soybean; terminated with herbicide in spring). Data from the 2009 through 2012 growing seasons were evaluated. Only during the comparably hot and dry 2012 growing season did residue removal affect yield with the LRR treatment resulting in greater soybean yield than MRR and HRR. Maize residue remaining in the field under the LRR treatment may have reduced soil water evaporation, increased soil water availability, and improved soybean productivity during the 2012 drought year. Grain moisture at harvest was greater while grain N and S concentrations were less in soybeans grown under LRR than under MRR or HRR across all years of the study. Greater residue amounts under LRR likely kept soil temperatures cooler which, in turn, would have slowed soybean plant development and reduced seed N and S uptake compared to the MRR or HRR treatments. There were no significant 2-way residue management by cover crop treatment interactions, suggesting that dependent variables responded similarly to residue management treatments regardless of the absence or presence of cover crops.