Projecting Climate Change Effect on Soil Water Fluxes and Urea Fertilizer Fate in the Semiarid Pampas of Argentina

Abstract

The economy of the semiarid region of the Argentine Pampas is based mainly on agriculture, so climate change is a fact that may have great influence on this type of activity. Therefore, it is necessary to evaluate future climate scenarios and the responses of hydrological variables such as precipitation, actual (ETreal) and potential evapotranspiration (ETc), and recharge rate. Climate change scenarios were based on temperature and precipitation variations predicted by CMIP5. Four representative concentrations pathways (RCP) were considered according to different greenhouse emissions to the atmosphere for the nearby future until the end of the twenty-first century (RCP2.6, RCP4.5, RCP6.0 and RCP8.5). Furthermore, one more scenario called RCP0.0 was considered, which is related to the actual climate conditions and represents the base line. In the study area, nitrogen (N) fertilization is a widely used practice to increase crop yields. This work assesses the impact of future climate on soil water fluxes and N compounds fate based on numerical simulations carried out with HYDRUS 1D. Actual evapotranspiration is going to increase between 1 and 6% from low to high climate-change scenarios. Although an increase in precipitation is also expected during all months of the year, there are periods when water availability will not be enough to supply the new potential evapotranspiration demand. The worst case is RCP8.5, where the ETreal/ETc ratio is expected to decline by 4%. Annual recharge is expected to decrease by 2.5% in the RCP2.6 scenario, while the rest of the scenarios shown positive trends. N leachate in the form of nitrates showed an increase of 2.8% in the RCP4.5 scenario which was also the one with the highest recharge rate raise. The use of a mathematical model as a predictive tool in soil water fluxes and fertilizers use is essential for planning the sustainable management of agroecology adapted to climate changes.