Post-Anthesis Nitrogen Loss from Corn
1993
Francis, D. D. | Schepers, J. S. | Vigil, M. F.
Published research has shown relatively large amounts of NH₃ being lost from aboveground vegetation during grain development for various grain crops For corn (Zea mays L.), maximum net N accumulation usually occurs during early reproductive development (R1-R3) and a subsequent decline is often observed. Two recently completed N fertilizer recovery studies on irrigated corn utilizing isotopic techniques were re-examined to quantify post-anthesis N losses from aboveground biomass of irrigated corn under different N regimes. These studies were conducted at different sites, in different years, with fertilizer rates ranging from 50 to 300 kg N ha−¹. Measured losses of labeled N from aboveground plant material ranged from 7 to 34 kg N ha−¹. Isotopic dilution suggests that apparent real N losses from aboveground biomass ranged from 45 to 81 kg N ha−¹, assuming there is no selectivity for N source (i.e., ¹⁵ N vs. ¹⁴N). Plant N losses accounted for 52 to 73% of the unaccounted-for N in ¹⁵N balance calculations. Failure to include direct plant N losses when calculating an N budget leads to overestimation of losses from the soil by denitrification, leaching, and ammonia volatilization. Proper accounting for volatile plant N losses may improve management strategies that affect N fertilizer use efficiencies. Published as Paper no. 9933, J. Series, Nebraska Agric. Res. Div., Lincoln.
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