Optimizing Irrigation Regimes and Intervals for Improved Water Productivity and Yield of Cucumber (Cucumis Sativus) in a Tropical Agroecological Zone

Abstract

This study evaluated the effects of four irrigation levels (R1: 100% ETc; R2: 75% ETc; R3: 50% ETc; R4: 25% ETc) and three irrigation intervals (D1: daily; D5: 5-day; D10: 10-day) on cucumber yield, fruit quality, and water productivity under tropical greenhouse conditions in southeastern Nigeria. A randomized complete block design (RCBD) with a 4×3 factorial arrangement and three replications was implemented over two growing seasons (2023–2024). Crop evapotranspiration (ETc) was calculated using the FAO Penman-Monteith equation, with water applied via calibrated drip irrigation. Key results revealed that both irrigation amount (IA) and interval (II) significantly (p < 0.001) influenced all parameters. Maximum fruit yield (151 t/ha in 2023; 123.1 t/ha in 2024), fruit weight (17.6 kg/plot), length (36.1 cm), and diameter (5.99 cm) occurred under full irrigation with daily application (R1D1). Yield declined progressively with reduced IA and extended II, with R4D10 yielding only 16.3 t/ha (2023) and 11.5 t/ha (2024). Water productivity (WP) peaked at 73 kg/m³ (R1D1, 2023) and 43.1 kg/m³ (R2D1, 2024), while irrigation water productivity (IWP) reached 81 kg/m³ (R1D1, 2023). Crucially, R2D1 (75% ETc daily) maintained competitive yields (92 t/ha in 2023; 87.1 t/ha in 2024) and high WP/IWP, indicating potential for significant water savings with minimal yield penalty. Interactions between IA and II were nonsignificant for yield, WP, and IWP but significant for fruit dimensions over time (p < 0.001).