Sistema silvipastoril com Urochloa brizantha cv. Marandu e Pterodon emarginatus: sucupira branca

The objective of this work was to observe and describe aspects related to climate, pasture, trees and soil characteristics over a year period of a silvopastoral system with signal grass (Urochloa brizantha) and leguminous trees of Sucupiras Brancas (Pterodon emarginatus), located at Campo Alegre Ranch in Itapecerica county, Minas Gerais state, Brazil. The experimental area had 61 ha divided in two: 26 ha of sole pasture (25 trees per ha scattered in the pasture) and 35 ha of silvopasture (SPS) (156 trees per ha). This system was established more than 30 years ago by putting down most of the cerrado vegetation and selecting the sucupira trees during pasture clearings. The area, therefore, did not receive any amendment nor fertilizers. At each season change (equinoxes and solstices) solar radiation data, soil and pasture samples were collected. Seasons influenced photossynthetic active radiation (PAR) in both areas and the leaf area index (LAI) in the SPS. There was an incongruence of resources among seasons of the year: when there were humidity and heat during summer, the amount of light transmitted under the canopies to the pasture diminished due to the LAI of the trees and cloudiness of the weather. When there was more light passing through the trees and less cloudiness during the winter, there was lack of humidity and temperature. Tolerance to shade criteria can not be used separately when choosing the grass to a silvopastoral system. PAR under the canopies represented 69% of total PAR during the year and allowed the pasture under the trees to produce 65% of the dry matter production of the non-shaded pasture. It was possible to conclude that silvopastoral system might bring benefits to land usage, improving physical, chemical and biological characteristics of the soil, enhancing holistic productivity (animal and vegetation), however, soil fertility and animal concentration demand adjustments because of nutrient extraction and lower pasture production under trees.