Phosphorus, nitrogen, and carbon stocks in semi-arid Chaco soil under different land uses

Abstract

 In order to determine if changes in land use affect carbon, nitrogen and phosphorus stocks, soil samples were taken at different depths (0-0.05; 0.05-0.15; and 0.15-0.30 m) from semi-arid Chaco Entisols under different land uses (treatments): Native forest, Silvopastoral system, Agricultural field planted with soybean under zero tillage, and Pasture implanted with Gatton panic (Megathyrsus maximus cv. Gatton panic). It could be concluded that during the study, when land use changed from native forest to pasture, the carbon stock was modified significantly up to 0.15 m. By contrast, when the shift was towards silvopastoral systems or an agricultural crop, there was an increase in carbon stock, but with lower values than those for pasture. The agricultural crop and native forest land uses showed a lower nitrogen stock on the surface, whereas this parameter was higher at a considerable depth in the case of implanted pasture. The phosphorus stock in these sedimentary soils showed the importance of growing native forests at greater depths, since the deepest stratum evaluated presented a higher value of this parameter, thus suggesting that nutrients are relocated at such depths. The results proved soil organic carbon to be a standardized parameter to monitor land uses and/or their changes in large regions like the semi-arid Chaco, where agricultural activities are continuously gaining ground