Tracing Nitrogen Movement in Corn Production Systems in the North Carolina Piedmont: A Nitrogen-15 Study
- Carl R. Crozier *,
- Larry D. King and
- Richard J. Volk
Legume cover crops have been studied in the southeastern USA, but there have been no 15N tracer studies comparing movement of legume N and fertilizer N for this region. Our study used l5N-enriched crimson clover (Trifolium incarnatum L.) (135 kg N ha−1) and either 15NH4NO3 or NH154NO3 (70 kg total N ha−1) to quantify N movement through soil inorganic and organic N pools and into corn (Zea mays L.). Clover N mineralized rapidly, with 45% of the initially applied N detectable as inorganic N at 18 d following incorporation. Rapid nitrification of enriched NH+4 occurred, but, since the soil NO-3 pool was larger in this treatment than in the enriched NO-3 treatment (presumably due to chance), the relative enrichment of the soil NO-3 pool was less than with the application of enriched NO-3. At anthesis, 25% of the N in corn had been derived from the NO-3 source, while only 11% had been derived from the NH+4 source (P < 0.05). At physiological maturity in 1990, the first growing season, 38 to 44% of each enriched source could be accounted for. By physiological maturity in 1991, 60% of the clover source but only 28 to 36% of the fertilizer sources could be accounted for. This study demonstrates the substantial amounts of endogenous soil N mineralization, inorganic N immobilization, and legume N persistence in these cropping systems.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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