Nitrogen fertilizer in sugarcane due to crop rotation, straw removal and nitrogen rates

Abstract

The straw which stay on the soil after the sugarcane harvest give for the plant-soil system many benefits. However this straw in the field produced many challenges to the fertilization and the nitrogen use efficiency (NUE). The NUE and the N-fertilizer immobilization by the straw are currently uncertain. Furthermore the interest in removing the straw to the field to product energy and ethanol can affect the NUE. The crop rotation with sunhemp can increase the availability of nitrogen in the soil and can improve the NUE. Thus it allows that the partial straw removal don't affect the productivity of the sugarcane. The author of this research have the objective to evaluate the NUE in area with crop rotation and straw removal during two crop season of sugarcane ratoon in clay soil with high potential of productivity. In the field was installed an experiment with experimental design consisted of randomized blocks with four replicates. The treatments are placed in two areas, one with crop rotation with sunhemp and other stayed without crop during the field renovation. After first sugarcane harvest in each area were installed the six treatments: controle, 60, 120 and 180 kg ha-1 of N (with 100% of straw) and two treatments with 0 (zero) and 50% of straw with 120 kg ha-1 of N. In the second ratoon was installed the microplots with ammonium nitrate - 15N (15NH415NO3) which was applied on the straw. The evaluates that will be do are NUE by the sugarcane in function of nitrogen rate, crop rotation with sunhemp and straw removal in different quantities. Furthermore the author will evaluate the 15N-fertilizer recovery in the soil, the 15N-fertilizer immobilization by the straw and the crop productivity. (AU)