EFFECT OF RAINFALL AMOUNTS ON MORPHOLOGICAL TRAITS AND PERFORMANCE OF WHITE YAM VARIETIES

ABSTRACT Rainfall variability is one of the major climatic factors influencing yam (Dioscorea rotundata) production in Nigeria. This study evaluated the effect of rainfall amounts on morphological traits and performance of three white yam varieties, Gambari, Abuja, and Idere, at the Teaching and Research Farm, Department of Crop Production Technology, Federal Polytechnic, Ado-Ekiti, during the 2025 cropping season. Rainfall was recorded weekly, and its effect on plant growth was assessed from 8 to 16 weeks after planting (WAP). Morphological traits measured included the number of leaves, vine length, leaf area, stem girth, and number of branches, while yield components included days to first flowering, tuber weight, tuber diameter, tuber length, and tuber yield per hectare. Results showed significant varietal differences (p < 0.05) in response to rainfall amounts. The Gambari variety consistently outperformed Abuja and Idere, with a higher number of leaves (128.3), vine length (236.4 cm), leaf area (128.6 cm²), and stem girth (7.6 cm) at 16 WAP. Yield performance was also superior in Gambari (26.4 kg/plot; 14.7 t/ha) compared to Abuja (12.5 t/ha) and Idere (11.6 t/ha). Reduced rainfall during critical stages of tuber initiation and bulking corresponded with reduced soil moisture storage and significantly limited morphological development and tuber yield in Abuja and Idere varieties. The study concludes that adequate rainfall distribution is crucial for optimum yam productivity and recommends the adoption of the Gambari variety in rainfall-prone zones due to its superior tolerance to rainfall fluctuations and better yield stability.