Management of nitrogen fertilization in cotton cultivated in crop rotation systems

Abstract

The no-tillage is one of the fundamental techniques for sustainable production systems, but it has some problems like immobilization in soil nitrogen, which often reduces crop yield. The objective of this work is to evaluate the dynamics of nitrogen (soil/plant) and yield of cotton in production systems with different crop rotations, rates and mineral N sources. The experiment is being conducted at the Experimental Farm of the University of Agrarian Sciences of Universidade do Oeste Paulista - UNOESTE, in Presidente Bernardes-SP. The soil in the area is sandy texture. Two experiments will be conducted in the 2018/2019 and 2019/2020 harvests seasons. The experimental design will be in randomized blocks with five replications, in a sub-subdivided plots scheme. The plots will be composed by the cultivation systems: forage, consortium 1, consortium 2, Mix and fallow; sub-plot: doses of N: 70, 100 and 130 kg ha-1; sub-subplot: N sources: common urea and protected urea. The hedge plants will be sown in April with desiccation in October. Cotton sowing in will be November, being the cultivar FM 983GLT. Nitrogen fertilization will be performed at 25 and 45 DAE, manually. Soil microbiology (enzyme activity, soil respiration, microbial biomass nitrogen and microbial biomass carbon), nitrogen in the soil will be evaluated in pre-sowing of the cotton, C/N ratio of straw and roots of cover crops, soil microbiology (N-total, N-NH4 +, N-NO3-) and fractionation of soil organic matter. At 25 DAE will be collected roots and aerial part for evaluation of nitrogen loaders in the plant. At 60 DAE will be collected cotton leaf and plant for evaluation of nitrogen content in the plant tissue and accumulation of dry matter. The IAF will be evaluated at 25, 50, 75, 100 and 125 DAE. At 70 DAE soil will be collected for evaluation of soil microbiology, soil protein and nitrogen in the soil. On the occasion of the physiological maturity of the cotton will be evaluated the production components (plants m-2, number of boll and average weight of bolls), cotton yield, yield mapping and fiber quality parameters (fiber strength, fiber length, fiber maturity and micronaire). After harvesting the cotton from the 2018/2019 and 2019/2020 harvests seasons, soil will be collected at depths of 0-10, 10-20 20-40, 40-60 cm for evaluation of inorganic nitrogen leaching from the soil (nitrate and ammonium). The statistical study will be performed by analysis of variance and the averages will be compared by the Tukey test at the minimum level of 5% probability, using statistical software Sisvar. (AU)