Optimizing Water and Nutrient Use Efficiency Through Deficit Irrigation and Fertilization Strategies in Cucumber (Cucumis Sativus L.)

Water scarcity and declining soil fertility are major constraints to sustainable vegetable production in sub-Saharan Africa, particularly under rain-fed and poorly managed irrigation systems. This study examined how deficit irrigation, together with integrated fertilization methods, affected water-use efficiency (WUE) and nutrient-use efficiency (NUE) in cucumber (Cucumis sativus L.) plants. The study utilized a Randomized Complete Block Design (RCBD) with three replications to conduct experiments in Asaba, Delta State, Nigeria. The study applied three irrigation treatments, including full crop water supply at 100% and reduced supplies at 75% and 50% of crop water need, together with two NPK treatments at 60 and 120 kg/ha, two poultry manure treatments at 3 and 6 t/ha, and control plots. Fruit yield fluctuated drastically over the course of the experiments; it ranged from 2.26 t/ha with I50N0M0 to 4.78 t/ha with I100N6M6, an increase of 111.5%. Full irrigation (I100) consistently produced the highest yield, with yields reduced by 8.9% to 12.1% under I75, depending on nutrient management. Still, the application of nutrient-rich treatment (N6M6) at I75 achieved a yield of 4.20 t/ha, which was only 0.58 t/ha lower than full irrigation. Water and concordant nutrient management showed significant main and interaction effects on yield in a two-way ANOVA, with highly significant main and interaction effects on fruit yield. Variability is about 5.67%, reflecting high precision in the experiments. This shows that adequate interaction between water and nutrient availability strongly influences cucumber yield, differentiating production and must lead to effective water use; the adoption of such strategies should not substantially hamper production. The results demonstrated that irrigation at 50%, combined with high manure application at 6 t/ha and high NPK application at 120 kg/ha, produced the best irrigation water use efficiency of 19.49 kg/m³ and water use efficiency of 16.73 kg/m³. Under full irrigation conditions with low NPK and high manure application, the study observed the highest nutrient use efficiency, achieving a yield of 26.00 kg per kilogram of nutrient. Post-harvest soil analysis demonstrated that integrated nutrient applications enhanced soil pH, organic matter content, total nitrogen, and available phosphorus compared with unfertilized controls. The combination of organic amendments and deficit irrigation resulted in significant increases in water productivity while maintaining yield levels. The study establishes that South-South Nigerian sandy loam soils achieve optimal water and nutrient use efficiencies through integrated nutrient management, which combines deficit irrigation with 60 kg/ha NPK and 6 t/ha poultry manure for cucumber production.