RESIDUAL EFFECTS OF NO-TILL CROP RESIDUES ON CORN YIELD AND NITROGEN UPTAKE

The residual effects of crop residues on N availability and crop growth are largely unknown. A field experiment was conducted from 1986 through 1988 at Lincoln, NE, to determine the residual effects on no-till corn (Zea mays L.) production and N uptake of 0, 50, 100, and 150% of the amount of crop residues produced by the previous crop during the previous 5 yr. These effects were evaluated with and without tillage (disking), N fertilizer (60 kg N ha(-1)), and hairy vetch (Vicia villosa Roth ssp. villosa, 'Madison') winter cover crop. Increasing the previous crop residue rate increased organic C, total N, and NO3-N in the upper 30 cm of soil as much as 10, 12, and 66%, respectively. Growth and N uptake by corn (3 yr average) generally increased as previous residue rate increased. Corn grain and stover production was 17 and 25% greater for the highest compared with the lowest previous residue rate. Uptake of indigenous soil N, but not fertilizer N, also increased as previous residue rate increased. Cover crops generally increased growth and N uptake with no fertilizer, but had little effect with N fertilizer. Soil properties, crop growth, and N uptake generally were not affected by tillage or interactions among the variables. These results indicate that increasing no-till crop residue rates increased the capability of this soil to provide N to growing crops for many years. It appears this effect is somewhat self perpetuating.