Effects and economically feasible rates of nitrogen and phosphorus fertilizers on potato (Solanum tuberosum L.) production for rainy season

Abstract

Potato is very important food and cash crop in Ethiopia. However, a factor like poor soil fertility is a critical challenge of its productivity. Nitrogen (N) and phosphorus (P) are first and second essential macro-elements and are limiting nutrient in potato production. Therefore, a field experiment was conducted to assess response of N and P fertilizers and select economically feasible fertilizer rate for a rainy season. Four levels of N (0, 55, 110, 165 kgha-1) and 4 levels of P (0, 45, 90, 135 kgha-1) were combined in 4×4 factorial arrangement in randomized complete block design with 3 replications. Raising the application of NP fertilizer levels to 165 and 135 kgha-1 delayed days to flowering (9.48 and 4.46 days), while maturity extends 14 and 10.18 at Dabark and Dabat, respectively. Application of 110 to 90 and 165 to 45 kgha-1 NP increased marketable tuber number by 122 and 119%, respectively. Similarly, 165 to 90 and 165 to 45 kgha-1 NP raised marketable tuber yield by 141.8 and 127.5%. However, both 165 to 90 and 165 to 45 kgha-1 NP had MRR below acceptable level (<100%). In contrary, application of 110 to 90 kg ha-1 NP resulted in 136.6 and 125.4% marketable tuber yield increment and MRR of 1993.72% for Dabark and 1376.5% for Dabat location. Therefore, application of 110 to 90 kgha-1 NP was proven to have high MRR and can be used for the studied areas.   Key words: Marginal rate of return, Solanum tuberosum, marketable tuber yield, interaction effect, main effect.