WABOL: A conceptual water balance model for analyzing rainfall water use in olive orchards under different soil and cover crop management strategies

Abstract

A water balance model developed to simulate the effect of different soil management alternatives, as for instance conventional tillage or cover crop, on soil water balance has been implemented in a user friendly interface in order to allow its use by technicians and other stakeholder in the olive sector. In spite of this simplified interface for the user, the model uses process-based methodologies to describe the key processes controlling water balance in rainfed olive orchards, such as runoff, deep percolation, cover crop growth, soil evaporation and olive and cover crop transpiration. Model predictions were evaluated using 3-year period of runoff and soil moisture data for different soil managements from an experimental field located in an olive orchard in Southern Spain. Comparison of simulated results with experimental data suggests that the model predicts satisfactorily runoff losses and soil moisture. Thus, annual runoff simulation provided a RMSE of 4.4 mm and the model efficiency was in general higher than 0.5. This suggests that the described model could be a useful tool for stakeholders to carry out a complete evaluation of different soil management alternatives in olive orchards. Finally, an example of an application of the model is presented. In this example, the model is used to evaluate the impact of using a cover crop, including different mowing dates, on the different components of the soil water balance compared to conventional tillage for the conditions of Cordoba, Southern Spain, using a 50 year long record. This exercise indicates that the use of a cover crop in these conditions have a negative impact on olive transpiration (25% average reduction), although this impact can be mitigated using an early date killing of the cover crop, March 15th for the conditions simulated in this exercise.