Evaluation of the AquaCrop model for winter wheat under different irrigation optimization strategies at the downstream Kabul River Basin of Afghanistan

Abstract

Afghanistan has an arid to semi-arid climate where irrigated agriculture largely depends on scarce irrigation water supplies from snowmelt from the high raised mountains. Under growing water scarcity, farmers not only need to use the available water more wisely but have to develop alternative options for coping water scarcity. Deficit irrigation schedule can be one of the options to mitigate the adverse impacts of water scarcity on crop production. In the current study, FAO’s crop water productivity model (AquaCrop) was calibrated and validated with field data in Kabul River Basin (KRB) for wheat crop to simulate four different water scarcity scenarios (S-A: business-as-usual scenario, S-B: refilling the soil profile to field capacity upon 50 % water depletion, S-C: refilling the soil profile upon 100 % depletion and S-D: refilling the soil profile upon 130 % depletion occurrence) for resultant yield, water productivity (WP) and biomass production. Two wheat fields, namely A and B were monitored intensively for soil moisture content, meteorological situation, irrigation application and post-harvest data. Results show that the measured WP was 1.4 kg m−3 ETa and 1.5 kg m−3 ETa whereas, the actual (measured) water use efficiency (WUE) was 0.58 kg m−3 and 0.66 kg m−3 for Field A and Field B, respectively. The WP of the scenarios S-A, S-B, S-C and S-D was 2.0-2.1 kg m−3 ETa (for plot B and A), 2.5 kg m−3 ETa, 2.74 kg m−3 ETa and 2.8 kg m−3 ETa respectively. Similarly, yield under these scenarios was 6.4 ton ha−1, 8.7 ton ha−1, 7.4 ton ha−1and 6.7 ton ha−1 respectively while the above ground biomass was 21.3 ton ha−1, 21.8 ton ha−1, 19 ton ha−1 and 18.3 ton ha−1 respectively. As a consequence, WP could increase by 92.8 %, 78 % and 95 % in S-B, S-C and S-D, respectively with reference to the measured WP. The optimized scenarios developed in this study can provide guidelines for policy makers and farming communities to mitigate the adverse impact of water scarcity through such innovative interventions.