INFLUÊNCIA DA TEXTURA E UMIDADE DO SOLO NO EFLUXO DE C-CO2 EM ENCOSTAS SOB PASTAGEM

Abstract

The soil respiration is the result of biological oxidation of organic matter and the development of the root system of plants, these activities are directly linked to moisture, temperature, structure and texture of the soil, the efflux of CO2 would be the emission of Gases generated by the respiration of the soil into the atmosphere. In declivous areas the physical and chemical characteristics may vary according to their slope, with this the relief also becomes one of the determinant factors for the CO2 emission values. Therefore, the objective of this study was to evaluate the soil C-CO2 efflux in three relief positions (shoulder, half slope and pediment) of two slopes under Brachiaria Pasture (Urochloa decumbens) with different ages (one hillside under pasture with 20 years of use, and A hillside under pasture with 2 years of use). The experiment was carried out in the Cow Brava watershed, located between the municipalities of Areia/PB and Remígio/PB. Soil samples were collected for physical analysis and quantity of water accumulated in each position, and the efflux of C-CO2 was evaluated in each of them over time. For data analysis, a 3x17 factorial scheme was used for Slope 1 and 3x15 for Slope 2 that correspond to the two slopes, a slope under 20 years of pasture and a hillside under pasture of 2 years, three positions of relief (shoulder, half slope and pediment) And the amount of efflux assessments performed on each slope, with three replications, totaling 306 samples. CO2 Efflux was evaluated monthly for 13 months by the amount of CO2 released from the soil surface for 24 hours, and captured in 40 ML of a sodium hydroxide solution (NaOH 1 Mol L-1), contained in a container within static chambers, by capturing carbon dioxide (CO2) within static chambers, by 40 mL of a sodium hydroxide solution (NaOH) at 1 Mol L-1 contained within a container for 24 hours. The mean values of the C-CO2 efflux were correlated with the soil moisture values, where it was observed that the highest values of C-CO2 efflux and the lower soil moisture levels were found in the pediment, due to its textural classification being sandy, which Facilitates the emission of gases and decreases water retention, it is also possible to observe that in the positions where there was excess water accumulated there was a decrease in efflux. It was concluded that among the positions of the slopes, the one that presented the highest emission values of C-CO2 was the pediment, on the two slopes under pasture, and that the soil texture is a determinant factor for the efflux of C-CO2.