Absorption and redistribution of fertilizer nitrogen, CO(15NH2)2, by two corn hybrids

Abstract

In an Oxic Paleudalf soil (Terra Roxa Estruturada) at the Escola Superior de Agricultura "Luiz de Queiroz" campus, the absorption and redistribution of fertilizer nitrogen by corn (Zea mays L.) (hybrids Cargill C-111X and C-511) at eight different sampling times, were studied, using tracer ¹⁵N. Fertilizers used were 100 kg N/ha (urea labelled with 5.86 atom % 15N), 80kg P₂O₅/ha (simple superphosphate), and 60 kg K₂O/ha (potassium chloride). Nitrogen was applied 1/3 at sowing and 2/3 at 42 days after germination (dag). Experimental design used was a split-plot: hybrids as plots and sampling times as sub-plots, with three replicates. It was shown that the percent nitrogen derived from fertilizer for the whole plant varied significantly (p = 0.05) for sampling time, having a maximum (33.65%) at 15 dag for the leaves and at 120-150 dag for the grain and whole plant. At flowering the plant absorbed about 50% of the fertilizer nitrogen absorbed during the entire cycle; at 120 dag about 60% of the nitrogen was derived from fertilizer; both hybrids had similar behaviours, and at the end of the cycle the leaves lost about 10% of the accumulated N.