Rainfall-Driven Variability Impact on Crop Water Productivity and Water Use Efficiency of White Yam (Dioscorea rotundata Poir.) Varieties in Southwestern Nigeria

Abstract

This study evaluated three white yam varieties namely, Gambari, Abuja White, and Idere for their physiological responses to rainfall-driven water availability during the planting season between March and October 2025. The experiment was laid out in randomized complete block design (RCBD) with three replications. Growth characters measured included Vine length, number of leaves, leaf area and Days to 50% flowering. Yield characters measured included Tuber yield (t/ha), tuber number, and tuber length at harvest. Result revealed significant variability in crop water productivity and water use efficiency among white yam varieties in Southwest Nigeria. Gambari variety consistently outperformed others, achieving the highest leaf area (1286 cm²), vine length (236.4 cm), and tuber yield (14.7 t/ha). Gambari exhibited superior water productivity metrics, with crop water productivity (CWP) of 2.75 kg m⁻³ and water use efficiency (WUE) of 58.18 kg ha⁻¹ mm⁻¹, surpassing Abuja and Idere varieties. These physiological advantages derived from Gambari's shorter growth duration, enhanced growth, and dry matter yield. Gambari's efficient rainfall utilization, better resilience to water stress, and superior water uptake efficiency make it a promising variety for improving water productivity and yield in Southwest Nigeria. It is suggested that farmers should prioritize early-maturing, water-efficient varieties (Gambari) in rain fed systems, particularly in areas with reliable early season rainfall but unpredictable mid-season dry spells.