NO-TILL CORN RESPONSE TO CROP-ROTATION AND IN-ROW RESIDUE PLACEMENT

Enhanced corn (Zea mays L.) yield responses to rotation in no-till sys tems mw be due to the types and amounts of surface-placed plant residu e, Research in 1989, 1990, and 1995 evaluated no-till corn yield respo nse to various preceding crops and examined whether in-row residue rem oval affected no-till corn response to rotation crops. The soil was an imperfectly drained loam (medium, mixed, weakly to moderately calcare ous Typic Hapludalf). The preceding crops were: corn harvested for gra in or whole-plant silage; hard red spring wheat (Triticum aestivum L.) ; barley (Hordeum vulgare L.); red closer (Trifolium pratense L.) cove r crops, following barley, that were killed of spraying either 3 wk (e arly-kill) or 1 d (late-kill) prior to corn planting; canola (Brassica napus L.); and soybean [Glycine max (L.) Merr.]. In-row residue was e ither retained while planting or cleared using planter-mounted, notche d-disk row cleaners, Clearing in-row cover crop residue increased earl y-season corn growth and was associated with yield increases of 0.61 M g ha(-1) (5%) following early-killed red clover and 0.43 Mg ha(-1) (6% ) (P = 0.10) following late-killed red clover, In 2 of 3 yr; corn yiel ds following party-killed red clover were similar to following soybean and greater than following grain corn, provided that in-row residue w as cleared, Following the other crops, grain yield response to clearin g in-row residue was smaller and less consistent over years. Preceding cropping affected early season corn growth, with the largest plants a t 5 wk after planting following either soybean or silage corn and the smallest following either red clover or grain corn, In 2 of 3 yr, when preceding crop effects on grain yield were statistically significant, yields following either soybean or spring wheat were more than 1.05 M g ha(-1) (16%) higher than after grain corn, That yield increase occur red regardless of in-row residue placement, Removing corn stover by ha rvesting as silage increased corn yield by 0.86 Mg ha(-1) (12%) over y ield following grain corn, During 1995, corn yield following silage ce nt was less than after soybean, canola, barley, or wheat; thus, no-til l coin yield response to rotation is not exclusively due to the presen ce of surface-placed stover. In-row residue placement and preceding cr opping practices affected in-row soil temperature, but this could not totally account for the treatment effects on early-season corn growth and yields.