Dinâmica da água e qualidade de pastagens no efluxo de CO2 em encostas de Argissolo Vermelho Amarelo

The productive capacity of the grassland is related to the age of establishment of these and the characteristics of the soil. In the Brazilian Northeast, grassland soils are generally in hillslope areas, slope hillslope favor variability in soil hydrodynamic properties and result in changes in physical and chemical characteristics. In addition, grassland cultivated on soil without fertilization depend on the cycling of nutrients from the grassland litter, process that results in efflux of CO2 into the atmosphere. Against the foregoing, this work was carried out, divided int three independent but complementary chapters. With the aim of determine the curves retention-θ(h) and hydraulic conductivity-K(θ) and the predominant retention force, use of the Beerkan method to obtain hydrodynamic soil parameters (Chapter I); to evaluate the efflux of CO2 from the soil, the production and quality of the forage and the litter of Urochloa decumbens (Chapter II); and determine the differences in soil CO2 efflux, forage production and quality of grassland of different ages (Chapter III). Chapters I and III were developed in three relief positions: shoulder, backslopes and footslope of two hillslopes under grasslands with different ages of establishment (one with 2 years of use-E2 and one with 22 years of use-E22). Chapter II was developed in the three relief positions, but only on a hillslope (E22). Soil water storage was evaluated using the Diviner 2000 capacitance probe. The hydrodynamic parameters were determined using the BEST model in the Sciliab program 5.3.3. The production of litter dry matter was evaluated with infiltration ring, already the production and the nutrient content in the grassland were obtained with exclusion cages, while the efflux of CO2 was quantified in static chambers. The results indicated granulometric variability among the topographic positions, and in E22 there is more clay than in E2. The water storage and the curves θ(h) and K(θ) varied according to the granulometric and hydrodynamic ...