Effect of Nitrogen and Phosphors Application on Yield and Yield Components of Improved Potato (Solanum tuberosum L.) Cultivars at Holetta, Central Highlands of Ethiopia

Abstract

An experiment was conducted at Holetta in 2012 main cropping season to study the effect of different nitrogen and phosphorus levels on yield components and yield of potato. The treatments consisted of two potato varieties (Jalenie and Gudanie), four levels of nitrogen (0, 55, 110 and 165 kg N ha^-1) and three rates of phosphorus (0, 90 and 180 kg P₂O₅ ha^-1). The experiment was laid out as a randomized complete block design with a factorial arrangement of 2× 4 x 3 with three replications. The study results indicated that increasing the rate of nitrogen from 0 to 165 kg N ha^-1 significantly increased fresh total biomass from 583 to 789 g/hill, similarly application of P significantly increased marketable tuber number by 19.72%. However N and P did not influence average tuber weight, dry total biomass, harvest index and unmarketable tuber yield. At the highest rate of nitrogen and phosphorus combination, highest marketable tuber yields were obtained for Jalenie variety (25.09 t ha^-1) and  Gudanie variety (30.52 t ha^-1) as compared to control treatment (Jalenie 11.41 t ha^-1 ) and (Gudanie 13.93t ha ^-1 ). The partial budget analysis data showed that the highest net benefit and marginal rate of return 41180 birr ha^-1 and 217%  and 52176 birr ha^-1 and 54 % for the variety Jalenie and Gudenie were obtained from N and P applied at 165 N kg ha^-1 with 180 kg P₂0₅ kg ha^{- 1} respectively . Therefore increasing the application of both nitrogen and phosphorous to the rate of 165 kg N ha^-1 and  180 P₂O₅ kg ha^-1 for the two varieties maximizes total and marketable yield and also have acceptable minimum marginal rate of return.