Effect of cumulative nitrogen fertilization on sugarcane (Saccharum spp.) cropped soils

Abstract

Nitrogen fertilizers interpret an important role in nutrition and increased yield of various crops, especially for sugarcane. Nitrogen fertilizers application causes series of changes in the chemical and biological properties due to their participation in the various microbiological soil processes, mainly related to the C and N cycle. This work aims to evaluate the effect of accumulated fertilizer nitrogen, in the mineral and organic forms, in the long-term soil nitrogen transformation processes, and carbon and nitrogen stock. Soil samples set will be collected in two experiments carried out in 2010 and 2011, which was adopted in the statistical design in randomized blocks with 6 treatments and 4 replications. The treatments applied in the implementation of the experiments and annually reapplied were T1 (control, without N fertilizer), T2 fertilization with organic compound (100 kg ha-1 N), T3, T4, T5 and T6 with doses of 50, 100, 150 and 200 kg ha-1 N, respectively. Annual soil samplings were performed in these experiments in the layers 0-20 and 20-40 cm, in which will be analyzed the variation in parameters of soil fertility and the content of hydrolysable organic N (ISNT). To evaluate the nitrogen fertilization effects on the N transformation processes in soil, samples will be collected in 2014 to 1.0 m depth in detail, in which we will be determined the content of organic C, total N and mineral N (N-NH4+ and N-NO3- + N-NO2-), as well as soil density. These samples will also be used in the incubation experiment in laboratory, assessing the potential of N mineralization and soil microbial processes through assessments of microbial biomass and basal respiration. (AU)