Do agrosystems change soil carbon and nutrient stocks in a semiarid environment?

Abstract

Ecological processes, such as net primary production, root system development, organic matter mineralization, nutrient removal and fertilizer application interfere in gains and losses of C and nutrients (N, P, K, Ca and Mg) in soils. Herein, we studied how five rainfed livestock and four irrigated agricultural systems affected soil C and nutrient stocks in a semi-arid environment. Soil concentrations, stocks, gains and losses of the nine land-uses were compared to those of the preserved native deciduous forest (Caatinga) along the top 1 m soil layer. Open Caatinga used as pasture, gliricidia and leucaena fields maintained the stocks of most nutrients. The shallower roots of buffel grass and prickly pear led to C (7 and 18%) and N (7 and 20%, respectively) losses, and P, Ca and Mg accumulations in the deeper layers. Irrigated crops reduced soil C and N stocks. C losses in irrigated maize and beans fields (23%) were lower than in rainfed fields in the region, while those in mango fields were large (70 and 66%). Fertilization in beans and grapes increased soil P and K stocks. Knowledge of stock changes allows proper system management to reduce the negative impacts of land-use change and promote sustainable production.