Effect of blended chemical fertilizer (sulfur, nitrogen and phosphorus) on yield and yield components of potato (Solanum tuberosum L.) in the rainy season

Potato is the fourth most important crop and consumed all around the world and is one of the main favorite vegetable in Ethiopia. However, the national productivity is very low as compared to the potential of the crop.  One of the main reason for low productivity is low soil fertility. Hence, a field experiment was conducted from 2016-2018 with 9 combination of nitrogen, phosphorous and sulfur fertilizers arranged in randomized complete block design with three replications to assess response of potato to these rates. The application 110-19.74-50.8 kg∙ha-1 N2/S2 /P2O5 fertilizer delayed days to flowering and maturity by 8 and 11 days at Darark and 10 and 14 days at Dabat. However, it increased plant height and number of stems per plant, which may positively contribute to increased photosynthetic area. The application of these fertilizers advanced marketable tuber yield by 153% and the total tuber yield by 86.6% relative to unfertilized plants. Furthermore, the partial budget analysis data showed that the highest net benefit and marginal rate of return (4453.6%) was obtained from 110-19.74-50.8 kg ha-1.  Therefore, the current study results is indicative that potato can grow well and provide better yield at Dabat, Dabark and similar agro ecology by using 110-19.74-50.8 kg ha-1 N2/S2 /P2O5, respectively.  Key words: Fertilizer, marginal rate of return, marketable tuber, yield.