Fluxos de energia, evapotranspiração e desenvolvimento de pastagens no agreste meridional pernambucano

Abstract

The dairy industry stands out as the main agricultural activity of the Wasteland South, and this region, despite having the highest rainfall of the Wild, is subject to periodic droughts. Efficient use of water in agriculture ensures the crop to this end to it is necessary to study the processes of evapotranspiration from pasture. Thus, the objective was to determine the energy fluxes and evapotranspiration in Entisol cultivated with pastures in rainfed agriculture, in the microregion of Garanhuns-PE. To determine the energy balance was installed a tower in the center of the experimental area, containing two sensors measure temperature and relative humidity, and wind speed at two levels (z1 = 50 cm, e z2 = 100 cm) above the canopy of the pasture. In addition to these sensors were installed a pyranometer, a radiometer, a sensor for measuring the wind direction, and a rain gauge charts. To measure the heat flow in the soil, flowmeters were installed in two places to a depth z1 = 5,0 cm, with a soil moisture sensor at the same depth, and two horizontally installed in the thermal probes depths z1 = 2,0 cm and z2 = 8,0 cm. All the measurements mentioned above were stored as averages every 30 minutes, except where the rainfall was estimated their total value in a data acquisition system from Campbell Scientific CR 1000. There were also the following determinations in the pasture height of the vegetation cover (canopy), biomass accumulation, leaf area index and evolution of the root system. The evaporation of the culture, on average, of 1,5 mm d-1, with a total of 543,43mm. Most of the net radiation (Rn), during the analysis of the pasture, has been consumed by the sensible heat flux (H) with 58%. The latent heat flux consumed 36% and the heat flow in the soil only 6% of Rn. The water availability influenced the production of green biomass and LAI, with the highest yields of biomass and LAI occurring in the higher water availability.