Potential mineralization of native soil nitrogen due to nitrogen sources and crop residue with relationships C/N contrasting

Abstract

The estimation of mineralization may be used to adjust the recommendations of nitrogen fertilization, once that nitrogen of labile fractions is released in the initial periods of mineralization process. For better utilization of fertilization with nitrogen by crops is necessary wide understanding of nutrient dynamics in the soil. So, are objectives of the research project: to evaluate rates of net mineralization and gross mineralization nitrogen in function of nitrogen forms and plant residues of C/N ratio contrasting in Typic Hapludox previously cultivated with sugarcane. The net mineralization experiment will be conducted aerobically for a period of 16 weeks. The design utilized will be completely randomized with nine treatments and trhee repetitions. Nitrogen fertilizers (enriched with 2 atom % 15N) will be applied as ammoniacal N - (15NH4)2SO4 and amidic N - CO(15NH2)2. The N rate used will be 50 mg kg-1 soil and plant residues of 5.3 g kg-1 soil (about 15 t ha-1) of sugarcane or soybeans shoot. The experiment of gross mineralization will be conducted for two days. The design utilized will be completely randomized with 18 treatments and three repetitions. Nitrogen sources will be applied as KNO3 and (NH4)2SO4, both marked with 25 atom % 15N. The evaluations will be: determination of lignin, cellulose and hemicellulose of plant residues, potential N soil mineralization, determination of inorganic N forms in the soil, 15N abundance in the soil, total nitrogen and soil carbon, and fractionation organic nitrogen, mineralizable C, total carbon and 15N recovery of the microbial biomass.Keywords: net mineralization, gross mineralization, Glycine max, Saccharum spp, fractionation of organic nitrogen, Illinois Soil Nitrogen Test (AU)