RESPONSE OF POTATO (Solanum tuberosum L.) TO POULTRY MANURE, MINERAL NITROGEN AND PHOSPHORUS FERTILIZERS AT HOLETA, CENTRAL ETHIOPIA

Potato (Solanum tuberosum L.) is an important food security and cash crop in Central highlands of Ethiopia. However, its yield is constrained by problem of soil fertility and poor fertilizer management. Therefore, a field experiment was conducted to assess the effects of poultry manure, mineral nitrogen and phosphorus fertilizers on yield and yield components of potato at Holeta, in 2012 growing season. The treatments consisted of factorial combination of 2 levels of poultry manure (PM) (0 and 5 t ha-1) and three levels of inorganic nitrogen (N) fertilizer ( 0 , 55 and 110 kg ha-1 ) and three levels of phosphorous (P) (Tri Super Phosphate) ( 0, 45 and 90 kgha-1 laid out in a Randomized Complete Block Design (RCBD) and replicated three times per treatment. Results demonstrated that significant main effect of PM on days to 50% shoot emergence, plant height, days to maturity, leaf area index, stem number, total tuber yield, mean tuber weight, marketable tuber number, total tuber number and tuber dry matter content. Application of N had also a significant effect on total tuber yield, marketable tuber yield, mean tuber weight and tuber dry matter content. Phosphorous also had an effect on shortening of the shoot emergence time. The maximum marketable tuber yield (18.63 tha−1 and 16.57 tha−1, respectively) were recorded in response to the application of poultry manure and nitrogen at the rates of 5 ton and 110 kg N ha−1 independently while the minimum marketable tuber yields (10.86 and 13.03 t ha−1 ) were recorded for the control treatment. Correlation analysis showed that total tuber yield was highly significantly and positively correlated with total tuber number (r= 0.909**), marketable tuber number (r=0.288*), plant height (r=0.747**) and main stem number (r=0.329*), leaf area index (r=0.732**), marketable tuber yield (r=0.989**) at 0.05 level. In conclusion, the findings indicated that the growth and productivity of potato at study area can be improved by the application of poultry manure and inorganic NP fertilizers. However, further study needs to be conducted at different seasons and locations to generate more reliable information.