Effect of Potassium Fertiliser on the Quality and Yield of Sweet Potato in Cross River State

This study examines the effect of different potassium fertiliser application rates on the yield and nutritional quality of sweet potato in Cross River State, South South Nigeria. Sweet potato is an important food security crop in Cross River State, valued for its high energy content, beta-carotene, and iron supply. Potassium is a critical macronutrient for root crop development, controlling starch synthesis, water uptake, and root bulking. However, potassium-specific recommendations for sweet potato under Cross River State soil conditions are limited. This study establishes a randomised complete block design experiment at the Cross River University of Technology research farm in Calabar, applying muriate of potash at five rates: 0, 30, 60, 90, and 120 kilograms of potassium oxide per hectare. Fresh root yield, dry matter percentage, beta-carotene content, glucose content, and marketable grade proportion are measured at 16 weeks after planting using Resisto variety. Findings reveal that 60 kilograms per hectare of potassium oxide achieves the maximum marketable fresh root yield of 24.8 tonnes per hectare, a 72 percent increase above the unfertilised control. Beta-carotene content peaks at 90 kilograms per hectare. Dry matter percentage is positively associated with potassium application up to 90 kilograms per hectare. Beyond 120 kilograms per hectare, yield declines due to potassium toxicity effects on calcium and magnesium uptake. The study concludes that 60 kilograms per hectare of potassium oxide is the optimal agronomic rate for sweet potato in Cross River State, and recommends its inclusion in state-level crop production guidelines.

Keywords: potassium fertiliser, sweet potato yield, beta-carotene, Cross River State, root quality.