Ciclagem de nitrogênio em sistema de integração lavoura-pecuária com irrigação e leguminosa forrageira

Abstract

In view of the increasing use of crop-livestock integration, it is of great importance to carry out studies to understand the operation of the most diverse types of integrated systems and to mitigate the doubts about these systems, so it is necessary to understand the nutrient cycling through the practices adopted these systems. In this context, the objective of this work was to evaluate the effect of legume and irrigation on nitrogen cycling in a crop-livestock integration system. The experiment was carried out in an area belonging to the Experimental Farm of UTFPR - Campus Dois Vizinhos during the period from April 2016 to March 2017. Four treatments were evaluated in a 2x2 factorial scheme (irrigated and non - irrigated x consortium and non intercropped with legumes) in a completely randomized experimental design with three replicates. During winter / spring the area was cultivated with black oats (Avena strigosa) and ryegrass (Lolium multiflorium) grown on African Star (Cynodon sp.), And in the intercropped pickets, vetch (Vicia sativa) was also implanted. During the summer period a picket of each treatment was cultivated with maize (Zea mays). To evaluate the nutrient cycling, the amounts of nitrogen returned to the soil via feces, urine, pasture residues and maize crop residues were determined. The data were submitted to analysis of variance and when they presented a significant difference, the Tukey test was performed at a 5% probability of error. There were no significant effects of irrigation or legume during the winter / spring period on the levels and nitrogen return of pasture, feces, urine and pasture residues, as well as similarities in N intake and retention animals. During the summer period, the evaluated factors also did not cause significant influences on the production of grains and straw, nor on the extraction, export and return of nitrogen by maize. Considering the total cycling in the system, it was observed a higher N export where there was no legume insertion (242.77 kg ha-1). The total return and the total amount of N cycling were in the mean of 335.61 kg ha-1and 567.13 kg ha-1, respectively, and were not significantly influenced by the evaluated factors. The use of irrigation and the legume consortium did not influence the nitrogen cycling in a crop-livestock integration system after one year of evaluation.