Utilization of nitrogen (15N) from sun hemp and millet by corn crop under no-tillage in Red Latosol of Cerrado

The cultivation of green manure in the fallow ground alter the dynamics and the recovery of the nitrogen by corn in the soil-plant system. The objective of this work was to evaluate the utilization of nitrogen (15N) from sun hemp and millet by corn grown under different N rates in no-tillage in Red Latosol of Cerrado. The research was carried in the Experimental Farm of Faculty of Engineering, Sao Paulo State University (UNESP), Ilha Solteira, located in Selvíria-MS, Brazil, during the 2001/02 and 2002/03 growing season. The experimental design was randomized complete blocks, with 15 treatments and four replications in a factorial 5 x 3, constituted by the combination of five N rates (0, 30, 80, 130 and 180kg ha-1), as urea, applied at four leaf stage; and three preceding cover crops: sun hemp, millet and fallow ground. The inorganic N promoted a synergic effect on the amount of absorbed N and utilization of sun hemp and millet N by the corn crop. The sun hemp, in average for two growing season, provided in the corn cultivated without the application of N an equivalent effect of the application of 56.0 and 73.0kg ha-1 as urea, compared to the corn grown in fallow soil and in succession to millet, respectively. The grain yield increased in a quadratic way in function of the N rates, in the two growing season.

Zea mays; labeled green manure; fallow; N mineralization; no-tillage

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