Water Productivity of Potato (Solanum Tuberosum) Under Deficit Sub-Surface Drip Irrigation and Super Absorbent Polymer in Clay Loam Soil

Abstract

The annual agricultural freshwater withdrawal in Kenya is high. With climate variability and competition from other water uses, irrigated agriculture is facing water shortage. The lack of adequate conditions for production and freshwater availability is causing more challenges for farmers. This has caused the production of Irish Potato, which is the second most grown and consumed crop in Kenya, a challenge for most farmers in arid and semi-arid areas. It is not possible to grow this crop in water-scarce situations since crop water requirements cannot be met. The use of deficit subsurface drip irrigation in the production of other crops has shown good quality yields and high water productivity. However, the water-saving potentials and the combined effect of super absorbent polymers and Deficit Subsurface Drip Irrigation (D-SDI) on potato production in water-constrained environments have not been adequately investigated. The study therefore sought to assess the water productivity of Irish potatoes using a deficit sub-surface drip irrigation system and super absorbent polymer. The field experiments were carried out under a transparent polythene shade in Tatton Agricultural Farm within Egerton University located in Nakuru County, Kenya. The field research was set out in a factorial experimental design, with twelve treatments, replicated three times. The treatments combined four quantity levels (0kg/ha, 6kg/ha, 10kg/ha, and 14kg/ha) of super absorbent polymer, and three irrigation levels (100%, 85%, and 70 %) of the crop water requirements (CWR). The study analyzed the impact of D-SDI and the amount of super absorbent polymer on potato yield and water productivity. The AquaCrop model was used to simulate the Irish potato and productivity in deficit irrigation and super absorbent polymer. The 100% water application level with 0 kg/ha super absorbent polymer was used for calibration and the other treatments were utilized to validate the model. The model predicted crop growth with R2 of 0.92, RMSE of 10.6%, NSE of 0.9, and Wilmot's degree of agreement of 0.98. The use of SAP in the soil, however, affected the model performance in simulation for various treatments. This was because the SAP improved soil characteristics relevant to water holding capacity without changing the physical texture and structure of the soil. The SAP and SDI combination showed an average of 12% improved yields under deficit irrigation with up to 39% water savings. For optimum potato production a row application of 10kg/ha SAP and 70% of potato crop water requirement was obtained from the study. The findings of this research can be adopted in improving food security on areas with water scarcity