DINAMIC OF NITROGEN ORGANIC FRACTION IN THE SOIL IN AREA WITH DEGRADED PASTURES FERTILIZED WITH NITROGEN RATES AND SOURCES

Abstract

The reconstruction of soil fertility is a major tool for the recovery of degraded pastures and nitrogen fertilizer use is of fundamental importance in its production process. This project aims to evaluate the fractions of organic and inorganic nitrogen from the soil that affect nutrition and recovery of pastures, as well as the utilization of nitrogen from nitrogen fertilizer, and also identify the source of nitrogen rate and economically viable to recover these pastures depending on the doses and fertilization with nitrogen sources. The research will be conducted with grass Brachiaria covering two stages: 1° stage: aerobic incubation experiment with soil from the area of degraded pasture to evaluate the potential mineralization and immobilization of nitrogen in the soil, depending on the applied rate and sources nitrogen, and 2° stage: A field experiment in the area of degraded pasture to assess the dynamics of soil organic nitrogen, the use of nitrogen from fertilizer, and economic viability of the recovery of pasture using sources and nitrogen, in the Cerrado. Will be tested nitrogen sources (ammonium sulfate, ammonium nitrate and urea) and nitrogen rates (0, 150, 300, 450 and 600 kg ha-1 yr-1). Will be evaluated in the first experiment, total organic carbon, total nitrogen content, soil nitrate and ammonium, and organic nitrogen hydrolyzed four times. Rate will be in the second experiment, the following changes from the supply sources and levels of nitrogen in grass Brachiaria leaf area, weight and number of tillers, dry weight of shoots and roots, SPAD value, activity enzyme nitrate reductase, chlorophyll (a, b and total), plant height, leaf: stem ratio, leaf area index, nutrient concentration in shoots and roots, recovery efficiency of nitrogen by Brachiaria and components analysis economical use of sources and levels of nitrogen. On the ground will be evaluating the levels of total organic carbon, nitrogen, nitrate, ammonium and fractions of soil nitrogen and hydrolyzed to end each season. To quantify the nitrogen balance is an installed application with microplot sources enriched in the isotope 15N. The results will be submitted to analysis of variance for the sources and levels of nitrogen and, with significance level of 5%. Otherwise, it will apply the procedure associated with ANOVA and Tukey's test regression study of first and second degree for the effects of nitrogen sources and rates of nitrogen, respectively. There must still be Pearson's correlations among attributes.