Tracing Nitrogen Movement in Corn Production Systems in the North Carolina Piedmont: A Nitrogen-15 Study
1998
Crozier, Carl R. | King, Larry D. | Volk, Richard J.
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.
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