Caracterização da forragem de capim-piatã e do microclima em sistemas de integração lavoura-pecuária-floresta, com dois arranjos de árvores de eucalipto

Abstract

Agricultural technologies use that aim the efficient land use, such as integrated crop-livestock-forest systems, are increasingly required in national agriculture. However, the heterogeneous microclimatic condition, caused by trees introduction, hampering a proper forage management definition in the cropping systems. Within this context, an experiment was carried out at Embrapa Beef Cattle, Campo Grande, Brazil, from January to December of 2011. Goal was to characterize the Piatã-grass forage (Brachiaria brizantha cv. BRS Piatã) and the microclimate in integrated crop-livestock-forest systems with two trees arrangements. To forage characterization, experimental design was complete randomized block, in split-plot design with two replicates. Plot treatments corresponded to a 2x2 factorial, with two grazing heights (low and high) and two distances between eucalyptus tree rows (14 and 22 m). Split-plot corresponded to sampling sites (five equidistant points between tree rows). To microclimate characterization, experimental design was complete randomized block, in split split-plot design with two replicates. Plot treatments corresponded to two distances between eucalyptus tree rows (14 and 22 m). Split-plot corresponded to the sampling spots (five equidistant points between tree rows), and split split-plot corresponded to day period (morning and afternoon). Average trees high were 12.44, in February, and 15.16, in August. At each point, with sample area of 1.0 m x 1.0 m, was realized the grass cutting, at ground level. Subsequently, was performed the Piatã-grass fractions separation (leaf, stem and senescent material) and weed (other Brachiaria). These fractions were placed in a forced circulation oven with air temperature of 55ºC, until reach constant mass. After pre-drying, the components (Leaf and stem) were fracked and sent to laboratory for crude protein, neutral detergent fiber, acid detergent fiber and in vitro digestibility of organic matter determination, through near-infrared sprectroscopy (NIRS). Then, on sampling sites, measurements were made of photosynthetically active radiation, by a portable ceptometer; temperature, air relative humidity (minimum and maximum) and wind speed, with portable thermo-hygro-anemometer. Locations near trees rows, lower high pasture and lower spaced trees rows had a lower and herbage dry matter and higher nutritional value. Higher pastures and greater trees spacing had grater variation of forage available and nutritive value. Places under shade had lower temperature and air relative humidity amplitude and higher maximum and minimum air relative humidity.