Revista Brasileira de Milho e Sorgo (Aug 2006)
ACCUMULATION OF NUTRIENTS IN COVER PLANTS AND BY CORN CROP IN SUCESSION UNDER DIFERENTS NITROGEN RATE IN NO-TILLAGE SYSTEM
Abstract
Nitrogen (N) is the mineral nutrient that is absorbed and exported in larger amount by corn crop. The objective of this work was to evaluate the amount of accumulated N by biomass and exported by corn grains cultivated under different N rates in succession to sun hemp (Crotalaria juncea), millet (Pennisetum americanum) and spontaneous vegetation (fallow ground) in no-tillage system; to verify the influence of N rates and cover plants in the tenor of mineral N of soil (N-NH4 + and N-NO3 -) in the layers 0 to 0.10, 0.10 to 0.20 and 0.20 to 0.40 m, and in the content in the leaves of macro and micronutrients of the corn by flowering and; to quantify the accumulation of macro and micronutrients in the above ground of the sun hemp, millet and spontaneous vegetation (fallow). The research was carried in the Experimental Farm of Faculty of Engineering, University of the state of S. Paulo (UNESP), Ilha Solteira, located in Selvíria-MS, Brazil, in a dystroferric Red Latosol, cerrado phase, 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, in the form of urea, applied during four leaf stage of corn (0, 30, 80, 130 and 180 kg N ha-1); and three preceding cover crops (sun hemp, millet and fallow). The sun hemp accumulated most of the macronutrients and micronutrients, promoting more extraction and exportation of N in the corn cultivated after the sun hemp, proportionally, than in succession to the millet or soil in fallow ground. The N exported was, in average, of 15.70 kg for ton of grains and returned by straw, of 8.30 kg for ton of crop residues.
