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OPTIMIZING PLANT POPULATION AND NPK FERTILIZER REGIMES
FOR ENHANCED FIELD PERFORMANCE OF YAM MINITUBERS
(Dioscorea rotundata) IN ABUJA, NIGERIA
Author(s): Khalid T. K. *, Gaya M.I ., Kalu G ., A Ambi ., Adam J.J ., Abdulkadir K ., Malami M . and Bilyaminu A.B
Volume/Issue: Volume 6 , Issue 1(2026)
ABSTRACT:
Yam (Dioscorea rotundata) remains a critical food and economic crop in Nigeria, yet its productivity is constrained by declining soil fertility, high production costs, and limited availability of quality seed yam. Recent advances in seed yam technologies have enabled large-scale production of clean minitubers; however, the field agronomy required to optimize their performance is not well established. This study evaluated the effects of plant population, NPK fertilizer type, and fertilizer rate on the growth and yield of field-grown yam minitubers under low-fertility savanna conditions in Abuja, Nigeria. A split–split plot experiment comprising three plant populations (266,000; 133,000; 88,000 plants ha⁻¹), three NPK fertilizer types (15:15:15, 20:10:10, 27:13:13), and four fertilizer rates (0, 200, 400, 600 kg ha⁻¹) was conducted over two seasons in 2023 and 2024. Results showed significant main and interaction effects across most vegetative and yield traits. The 133,000 plants ha⁻¹ population produced the highest fresh tuber yield (~17.5 t ha⁻¹), while the lowest density (88,000 plants ha⁻¹) produced the largest individual tubers, demonstrating a clear density-driven yield–size trade-off. Among fertilizer types, NPK 15:15:15 outperformed 20:10:10 and 27:13:13 for yield and tuber weight, reflecting the importance of balanced nutrient supply on nutrientdepleted soils. Yield responses peaked at 400 kg ha⁻¹, declining at 600 kg ha⁻¹ due to excessive vegetative growth. A strong three-way interaction (population × fertilizer type × rate) identified 133,000 plants ha⁻¹ × NPK 15:15:15 × 400 kg ha⁻¹ as the optimal combination for maximizing yield. These findings provide evidence-based agronomic recommendations to support sustainable intensification and improved seed yam production systems in the West African savanna.
KEYWORDS:
Yam minitubers; plant population; NPK fertilizer; tuber yield; growth physiology
