Response of Soil Chemical Properties, Performance and Quality of Sweet Potato (Ipomoea Batatas L.) to Different Levels of K Fertilizer on a Tropical Alfisol

摘要

Background: The optimum rate of nutrient must be defined with reference to soil properties for individual crops and soil. Objective: Field experiments were carried out in 2015 and 2016 cropping seasons to determine the various levels (0, 40, 80, 120 and 160 kg ha-1) of potassium fertilizer (muriate of potash , KCl), on soil chemical properties, leaf nutrient contents, performance and proximate quality of sweet potatoes (Ipomoea batatas L.). Method: The five treatments were arranged in a randomized complete block design with three replicates. Results: Studies showed that K fertilizer in both the years significantly influenced N, P and K concentrations compared with the control and also increased the soil concentrations of these nutrients from 0 - 160 kg ha-1 K fertilizer. However, soil K only increased up to 80 kg ha-1 fertilizer after which there was a decrease. There was a reduction in the values of Ca and Mg in the soil as the levels of K increased. Leaf nutrient concentration of the sweet potato was consistent with the values of soil chemical properties recorded. 80 kg ha-1 K fertilizer was observed to be the highest value of sweet potato growth and tuber yield after which there was a reduction. The yield decrease was adduced to excessive K application leading to imbalanced sweet potato plant nutrition compared with N, P, Ca and Mg. K fertilizer significantly influenced moisture, vitamin C and carbohydrate compared with the control. The highest values of fibre and protein were obtained at 80 and 40 kg ha-1 K fertilizer, respectively. Dry matter and fat contents of the sweet potato reduced by K application from 0 - 160 kg ha-1 application rate. Conclusion: For best tuber yield, quality and economic response of K fertilizer to the sweet potato in the agro-ecological zone or in other similar soil conditions elsewhere in the tropics could be achieved by applying 80 kg ha-1 K fertilizer.