Yield and water use efficiency of barley under different irrigation scheduling methods in southern Tunisia

摘要

In southern Tunisia,having less than 200 mm of annual precipitation,saline shallow ground water is used for irrigation.This study evaluated the effectiveness of the different irrigation scheduling methods and the automatic irrigation by comparing net income with a virtual water price.Barley was cultivated with drip irrigation.First treatment was “full” irrigation(FI)in which amounts required to replenish the root zone to field capacity was applied when the estimated readily available water was depleted.Second and third treatments were 0.7 and 0.5 times of amount but the same timing as first one.Fourth was deficit irrigation but only during maturity stage(DIM50).Fifth was an automatic irrigation system which applied 20 mm water when the monitored water content reached below a threshold value.Sixth was simulated irrigation in which optimized amount of water was applied every 4 days using a numerical model,WASH_2D,that simulates water,solute,and heat transport and crop response in two dimensions.Results showed that automatic and simulated treatments attained higher yields but the total applied depths were also high.The other treatments which applied less depth gave lower yield and net income but water use efficiency(yield per unit irrigation depth)was higher than automatic and simulated irrigation treatments.The highest net income was obtained in automatic irrigation.On the other hand,the highest water use efficiency was obtained in DIM50.