Evaluación mediante técnicas de simulación directa e inversa del cambio del flujo y lixiviación de suelo con un cultivo de cubierta de verano en el sur de Florida

This study was designed to measure the impact of sweet corn (Zea mays L.) production under South Florida subtropical conditions on groundwater quality and to determine the extent to which this impact may be reduced by use of the leguminous summer cover crop sunnhemp (Crotalaria juncea) as a potential best management practice. Water and nitrogen (N) inputs and outputs were measured during three corn seasons in an experimental field divided in six plots. Three of them were rotated with sunnhemp in the summers, before the winter corn seasons (CCC plots), while the other three were kept fallow (SCC plots). Crop management was identical in both types of plots during the winter seasons. A numerical model (WAVE) for describing water and agrochemicals movement in the soil was used to simulate water and N balances in both types of plots during the last two seasons. Soil moisture data at three depths continuously measured during the two corn seasons were used to calibrate the hydrodynamic component of WAVE. Model performance was successfully tested, yielding coefficients of efficiency of 0.85 and 0.91 for CCC and SCC plots, respectively. The parameters involved in the N balance were obtained by direct methods. This study indicates that although the sunn-hemp cover crop resulted in an improvement in the soil physical conditions and subsequent enhanced crop evapotranspiration and soil drainage reduction, it can also result in net increases of N leaching loadings towards the shallow aquifer. The use of this summer leguminous cover crop must be coupled with a reduction in the winter crop N fertilization to account for the net increase in soil N content.