Residual Effects of Crop Residues on Grain Production and Selected Soil Properties

Returning crop residue improves water conservation and storage, nutrient availability, and crop yields. We have little knowledge, however, of the residual impacts of crop residues on soil and crop production. We hypothesized that residual impacts of crop residues vary 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 crop residue amounts on crop growth and selected soil properties. From 1978 through 1985, crop residues were returned at 0,50, 100, and 150% of the quantity produced by the previous crop (averaging 0 to =6 Mg ha-' yr-I). 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-'), and hairy vetch (Vicia villosa L.) cover crop. Residual effects of the 150% residue amount increased grain production 16% compared with the 0% amount (4900 vs. 4250 kg ha-', respectively), and were not affected by time or other management practices. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclavemineralizable N ha-') and Bray soil P (16.7 to 20.3 kg ka-'). These results are among the first to show that residual effects of crop residue are prolonged (half-life of = 10 yr) and probably result from changes in soil properties that enhance soil nutrient availability. ESULTS FROM NUMEROUS STUDIES have shown that R various amounts of crop residues affect soil properties and crop yields (Black, 1973; Larson et al., 1972). Usually those studies showed that returning increased amounts of crop residues to the soil increased soil organic matter content, microbial activity, nutrient availability, water infiltration and storage, and crop yields (Unger and McCalla, 1980; Fribourg and Bartholomew, 1956; Prasad and Power, 1991). Effects of crop residue amount were sometimes modified by other management practices such as type of tillage, fertilization, and use of cover crops (Maskina et al., 1993). Understanding the effects of crop residues on soil properties and crop yields may be of greater importance USDA-ARS, 119 Keim Hall, Univ. of Nebraska, Lincoln, NE 685830934. Received 6 Jan. 1997. *Corresponding author (jp32349@ navix.net). Published in Soil Sci. Soc. Am. J. 62:1393-1397 (1998). in the future because of interest in using crop residues for production of paper products and ethanol. This is in addition to the conventional use of crop residues for fodder and bedding. Unfortunately, we presently have little information to evaluate the long-term impact of returning crop residues on soil productivity. We presently do not know the magnitude or duration of the effects of crop residue management practices on soil properties and crop production after we cease to use these practices. Therefore, we conducted an experiment to evaluate the duration and magnitude of the residual effects of various amounts of crop residues on soil properties and crop yields after we ceased returning crop residues in various amounts. This experiment involved production of corn (sorghum in years when planting was delayed) using N fertilizers and no-till practices, to be consistent with practices used in earlier experiments (see below). It is conceivable that the management practices used for crop production could alter the type of response we obtained to the residual effects of using various crop residue amounts. Therefore, a second objective of this experiment was to determine how residual effects of previous crop residue amounts were impacted by tillage method, N availability, and use of winter cover crops.