Response of Bread Wheat (Triticum aestivum L.) to Potassium (K) and Blended NPS Fertilizer Rates in the Nitisols of Southern Ethiopia

Wheat is the most important cereal crop ranking 4th in total grain production and area coverage in Ethiopia. However, its productivity is low compared to the yield obtained under the research station. Multinutrient deficiency, low/no chemical fertilizer usage, and poor management practices are among the major constraints. Thus, response of bread wheat to NPS and K fertilizer rates was evaluated in the nitisols at Kokate, Wolaita Sodo, Southern Ethiopia, in 2016. Four rates of KCl (0-0-60) (0, 25, 50, and 75 kg·ha−1) and five blended NPS (19N-38P2O5-7S) rates (0, 50, 100, 150, and 200 kg·ha−1) were investigated using randomized complete block design with factorial arrangement involving three replications. Soil physical and chemical properties, crop phenology, growth parameters, yield components, and yield data were collected. Analysis of variance showed that crop phenology, productive tillers, and straw yield were significantly affected by KCl and NPS fertilizer rates; however, most of growth parameters, yield components, grain yield, and agronomic efficiency were influenced by the interaction effects of KCl and NPS fertilizers. Combined application of 50 kg·ha−1 KCl and 150 kg·ha−1 NPS resulted in highest growth, yield component, grain yield, agronomic efficiency, and economic return, whereas the lowest measured values were recorded from unfertilized plots. The maximum grain yield (4.34 t ha−1) that was recorded from 50 kg·ha−1 KCl and 150 kg·ha−1 NPS was 8.86-fold higher than the minimum yield (0.44 t ha−1) from the control. It is concluded that 50 kg·ha−1 KCl and 150 kg·ha−1 NPS are suggested for better agronomic and economic performance of wheat. As NPS was tested in the blended form, the individual and interaction effects of nutrients under investigation are suggested as future research areas. Additional investigation over season and location is also recommended.