RESIDUAL EFFECTS OF CROP RESIDUES ON GRAIN PRODUCTION AND SELECTED SOIL PROPERTIES

Returning crop residue improves water conservation and storage, nutrie nt availability, and crop yields, We have little knowledge, however, e r, of the residual impacts of crop residues on soil properties and cro p production. We hypothesized that residual impacts of crop residues v ary with the amount of residues used. A 10-yr study near Lincoln, NE, evaluated the residual effects of an earlier 8-yr study of various cro p residue amounts on crop growth and selected soil properties. From 19 78 through 1985, crop residues were returned at 0, 50, 100, and 150% o f the quantity produced by the previous crop (averaging 0 to approxima te to 6 Mg ha(-1) yr(-1)). Continuous corn (Zea mays L.) was produced 1986 through 1995 on these plots, except sorghum [Sorghum bicolor (L.) Moench] was substituted in several years. To study management effects on residual responses, plots were subdivided with or without tillage, N fertilizer (60 kg N ha(-1)), and hairy vetch (Vicia villosa L.) cov er crop. Residual effects of the 150% residue amount increased grain p roduction 16% compared with the 0% amount (4900 vs. 4250 kg ha(-1), re spectively), and were not affected by time or other management practic es. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclave-mineralizable N ha(-1)) and Bray soil P (16.7 to 20.3 kg ka(-1)). These results are among the first to show that residual effects of crop residue are prolonged (half-life of app roximate to 10 yr) and probably result from changes in soil properties that enhance soil nutrient availability.