Detectability of15N-depleted fertilizer N in soil and plant tissue during a corn-rye crop rotation |
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| Authors: | D C Ditsch M M Alley K R Kelley Y Z Lei |
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| Affiliation: | (1) Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, 24061 Blacksburg, VA, USA;(2) Agricultural Research Department NFERC/TVA, 35660 Muscle Shoals, AL, USA;(3) Soil and Fertilizer Institute, Liaoning Academy for Agricultural Sciences, Shenyang, China |
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| Abstract: | Use of15N-depleted fertilizer materials have been primarily limited to fertilizer recovery studies of short duration. The objective of this study was to determine if15N-depleted fertilizer N could be satisfactorily used as a tracer of residual fertilizer N in plant tissue and various soil N fractions through a corn (Zea mays L.) -winter rye (Secale cereale L.) crop rotation. Nitrogen as15N-depleted (NH4)2SO4 was applied at five rates (0, 84, 168, 252, and 336 kg N ha–1) to corn. Immediately following corn harvest a winter rye cover crop treatment was initiated. Residual fertilizer N was easily detected in the soil NO
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-N fraction following corn harvest (140-d after application). Low levels of exchangeable NH
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-N (<2.5 mg kg–1) did not permit accurate isotope-ratio analysis. Fertilizer-derived N recovered in the soil total N fraction following corn harvest was detectable in the 0 to 30-cm depth at each N rate and in the 30 to 60 and 60 to 90-cm depths at the 336 kg ha–1 N rate. Atom %15N concentrations in the nonexchangeable NH
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-N fraction did not differ from the control at each N rate. Nitrogen recovery by the winter rye cover crop reduced residual soil NO
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-N levels below the 10 kg ha–1 level needed for accurate isotope-ratio analysis. Atom %15N concentrations in the soil total N fraction (approximately one yr after application) were indistinguishable from the control plots below the 168, 252, and 336 kg ha–1 N rate at the 0 to 30, 30 to 60, and 60 to 90-cm depths, respectively. Recovery of residual fertilizer N by the winter rye cover crop was verified by measuring significant decreases in atom %15N concentrations in rye tissue with increasing N rates. The greatest limitation to the use of15N-depleted fertilizer N as a tracer of residual fertilizer N in a corn-rye crop rotation appears to be its detectibility from native soil N in the total N pool.Research partially supported by grants from the National Fertilizer and Environmental Research Center/TVA and the Virginia Division of Soil and Water Conservation. |
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| Keywords: | Exchangeable NH
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-N NO
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-N nonexchangeable NH
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-N Fertilizer N Uptake N15-depleted 15N isotope |
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