Crop Physiological Responses to Potassium Deficiency in Nigerian Farming Systems: From Leaf Biochemistry to Yield Formation

This study investigates crop physiological responses to potassium deficiency across the continuum from leaf biochemistry to yield formation in Nigerian farming systems, addressing a significant research gap as potassium deficiency is increasingly recognised as an emerging yield-limiting constraint. Historically, nitrogen and phosphorus have received the most research attention in Nigerian agronomy, but the recent depletion of soil potassium reserves under intensive farming without potassium replacement is creating widespread and previously underdiagnosed potassium deficiency, particularly in yam, cassava, and banana-plantain systems. This study establishes potassium omission trial experiments on four crops: cassava, yam, banana, and sorghum, at sites representing contrasting soil types in Benue, Delta, and Ogun States. Leaf potassium concentration, stomatal conductance, relative water content, Rubisco activity, starch biosynthesis enzyme activity, harvest index, and yield are measured at multiple growth stages under potassium sufficient and deficient conditions. Critical potassium concentrations for each crop are determined from foliar concentration-yield response curves. Findings reveal that cassava and yam show significantly lower critical potassium concentrations than international reference values, suggesting adaptation to low-K conditions, but yield penalties below these thresholds are substantial, reaching 48 percent in cassava. Potassium deficiency reduces starch biosynthesis enzyme activity by 34 percent and stomatal conductance by 28 percent, linking biochemical changes to yield formation impairment. The study contributes original potassium physiology data for Nigerian staple crops and recommends tissue testing adoption for potassium status monitoring in high-value crop systems.

Keywords: potassium deficiency, crop physiology, yield formation, cassava, Nigerian farming systems.