Produtividade de milho silagem em consorciação com forrageiras tropicais e adubação nitrogenada em sistema de integração lavoura-pecuária

Abstract

The adoption of integrated systems, in particular the Crop-Livestock Integration, is an alternative for sustainable management and when conducted correctly, brings numerous benefits, constituting a model of sustainable intensification of land use. Thus, the aim of this study was to evaluate the effect of single corn crop and intercropped with tropical grasses, conducted in a crop-livestock integration system, in the presence or absence of nitrogen fertilization, on the agronomic characteristics and productivity of corn for silage, soil physics properties, decomposition and release of nutrients from forage residues. The experiment was carried out between October 2017 and January 2020 (two agricultural years), in Marechal Cândido Rondon - PR, in random blocks in a split-split plots design with an additional control, with four repetitions. The plots consisted of two forage species (Urochloa brizantha and Magathyrsus maximum), plus the additional control (single corn crop). The subplots consisted of forage management (hay and grazing) and in the sub-subplots, the presence or absence of nitrogen fertilization. In corn, the final plant stand, plant height, spike insertion height, stem diameter and total dry matter productivity were determined. With the end of management and prior to corn crop implantation, macroporosity, microporosity, total porosity, soil density and soil resistance to penetration were determined. The rate of decomposition and release of nutrients from forage crop residues during the cultivation of corn for silage in succession was evaluated. The consortium did not compromise the production and increased 5 tons of dry matter productivity of corn silage. The use of corn intercropped with tropical perennial grasses is a viable option for the producer, for providing grazing in the period between harvests and/or straw to maintain the no-tillage system. The use of N in cover in forages after management, increased the amount of macropores in the 0-0.05 m layer for the first year. The Ds values are above the limit considered critical for the development of the plants, however, with a tendency to decrease. The adoption of the integrated system, regardless of the forage species used and management adopted, be it hay or grazing, does not compromise the physical quality of the soil, thus being a great alternative for the diversification of production on the property. The intercropping of corn and forage crops is an alternative to increase the amount of plant residues and nutrient cycling. Higher yields of dry matter and nutrient accumulation was obtained when forages were grazed, guaranteeing amount above 4,000 kg ha-1 of dry matter for continuity of the no-tillage system. On the other hand, haymaking must be carried out with great discretion as it greatly reduces the deposition of mulch in the soil and consequently the cycling of nutrients. The use of U. brizantha and M. maximum for animal feed, in integrated systems, is a viable alternative for the recycling of nutrients. The corn consortium with tropical perennial grasses is an option for the producer, as it provides pasture during the entry and / or straw for the maintenance of the no-tillage system.