Resumo

BARRIOS, Marta; GARCIA, Judith  e  BASSO, Carmen. Effect of nitrogen fertilization on nitrate and ammonium contents in soil and corn plant. Bioagro [online]. 2012, vol.24, n.3, pp.213-220. ISSN 1316-3361.

Maize requires large amounts of N and therefore it is necessary to generate information about best N sources and rates in order to improve the nitrogen use efficiency. The experiment was conducted at the Agronomy School, Universidad Central de Venezuela, to evaluate four nitrogen sources on nitrification rate, and nitrate and ammonium contents in soil and plant. The experimental design was a complete randomized block with four repetitions. The four nitrogen sources applied to soil were: regular urea; ammonium sulfonitrate + 3.4-dimethilpyrazol phosphate, urea-ESN, and ammonium sulfate, all of them split in two fractions. Plots contained six rows spaced 0.9 m apart, and 0.25 m between plants. Two nitrogen rates (55 and 92 kg·ha^-1 N) were combined to generate eight treatments in factorial arrangement, plus a control without nitrogen. Additionally, 20 kg·ha^-1 TSP, and 60 kg·ha^-1 KCl, were applied. Two soil and sap sampling were carried out at 42 and 62 days after planting (dap). Nitrate and ammonium in soil were determined by ion analyzer; sap ammonium was quantified by fluorescence spectroscopy using HPLC, and nitrate using an ion selective electrode. The nitrate inhibitor 3.4-dimethilpyrazol phosphate showed more effectiveness on nitrification rate retardation in most of cases. At 42 dap ammonium and nitrate concentrations in sap were higher than at 62 dap, whereas in soil they were lower, which is consistent with plant absorption rate.

Palavras-chave : Regular urea; ammonium nitrate; 3, 4-DMPP; urea-ESN; fluorescence spectroscopy; HPLC.

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