MODELLING OF POTATO CROP WATER PRODUCTIVITY AND YIELD RESPONSE UNDER SUBSURFACE DRIP IRRIGATION SYSTEM

Abstract

The need for increased food production by applying low water quantity is pausing more challenges to farmers. The production of Irish Potatoes in Kenya in arid and semi-arid areas is challenging for most farmers due to low yields. The purpose of the study was to simulate potato crop water productivity. A field experiment was conducted at Egerton University during the 2021-2022 dry season. The effect of deficit subsurface drip irrigation allied with superabsorbent polymer soil amendment on growth parameters and yield of potatoes was evaluated. Twelve treatments composed of three water application levels 70%IL, 85%IL,100%IL and four super absorbent polymer (SAP) application rates No SAP, 6 kg/ha, 10 kg/ha,and 14kg/ha laid in factorial experimental design were applied in December 2021 to May 2022 season. Irrigation was undertaken when the allowable water depletion reached 50%. The AquaCrop model was utilised to predict soil water content, biomass, canopy cover, dry yield, and water productivity (WP). The 100% water application level with 0kg/ha SAP was used in model calibration, whereas the remaining treatments were used to validate the model. The model simulated results compared with observed canopy cover, biomass and WP produced a good performance fit with R2 range of 0.86 to 0.98, root mean square error (RMSE) of 10.6%, NSE of 0.9, and Wilmot's degree of agreement of 0.98. However, the model underestimated the water content due to the application of SAP in the soil. Because the SAP improved soil characteristics relevant for water holding capacity without changing the physical texture and structure of the soil. The findings indicated that the combined effect of SAP and subsurface drip resulted in increased yield in deficit water application. The calibrated model was successfully applied in simulating WP and yield. The calibrated AquaCrop model can be applied in planning, operation and management of potato-irrigated farms that will lead to improved water productivity and yield in water constrained areas like semi-arid Kenya.