MANAGEMENT PRACTICES ASSESSMENT USING AQUACROP MODEL FOR GROWING BARLEY UNDER SALINE CONDITIONS OF THE ARID REGIONS OF TUNISIA

FAO's Aquacrop is one of the most suited models to water limited and saline conditions. It can help to assess management practices and allows developing better informed decisions concerning management and environmental factors that affect crop production. In this study, Aquacrop was used to determine the acceptable threshold of initial soil salinity and the suited period for sowing barley. Three initial soil salinity levels (3, 6 and 8 dS m(-1)) were evaluated under different initial soil water content for full (FI) and deficit irrigated barley and two contrasting seasons. Barley yield was predicted also for 8 consecutive sowing dates including the sowing dates used by famers. The model simulations were evaluated using statistical indicators (Root Mean Square Error (RMSE), Mean Bias Error (MBE), Mean Absolute Error (MAE) and the coefficient of determination (r(2)) and the three season's experimental data. Results show that grain yield and final biomass decrease with delay of sowing date and these reductions were accentuated with high initial soil salinity and the variability of rainfall events. The most suitable period for sowing barley ranging between end of November and the beginning of December. Initial conditions affect yield while the yield reduction started to be considerable (30%) only with the relatively higher level of soil salinity (8 dS m(-1)) and for dry season and deficit treatment. The comparison between measured and simulated yield and biomass under varied sowing dates and initial soil salinity shows good agreement with RMSE ranging between 0.36 and 1.6 t ha(-1), MAE ranging between 0.29 and 1.48 t ha(-1), r(2) about 0.77 and 0.81 for yield and final biomass, respectively. Aquacrop could be a useful tool to determine the optimum barley yield for different restricted factors.