Nutrient and phytotoxic contributions of residue to soil in no-till continuous-corn ecosystems

Summary An understanding of no-till ecosystems is essential for increased acceptance of conservation tillage practices. The primary objective of the present research was to assess the nutrient contributions of leachates from decomposing corn residue to soil in continuous-corn no-till ecosystems. A secondary objective was to estimate the phytotoxic effects of these leachates on corn seedling growth. The effects of moisture, temperature, and resident and non-resident microflora on leachates recovered from decomposing surface-applied corn residue were also studied. Leachates were analyzed for organic C, total N, PO₄^3–-P, acid and alkaline phosphatase activity, urease activity, and phytotoxic effects. Within the first 90 days of a 215-day field study 73%, 83%, and 60% of C, N, and P, respectively, were leached. In terms of nutrient concentration, this suggests two distinct phases of release of nutrients onto the soil: A high initial flux of nutrients that is followed by a low-concentration release. No phytotoxic effect of field leachates was observed. Acid and alkaline phosphatase activity was highest on days 39 and 47 whereas urease activity peaked on day 149. In laboratory studies, alterations in temperature or moisture had little effect on the leachate nutrient concentration, or phytotoxic or enzyme activity. Increasing amounts of organic C and N were extracted over time. No phytotoxic effects were expressed in the laboratory. Overall, it appears that the maximum leaching of nutrients occurs early in the decomposition process and that in no-till systems no phytotoxicity can be associated with decomposition of surface residues.Paper No. 11871 of the Purdue University Agricultural Experiment Station Series