Combined effects of inorganic (NP) and organic (FYM) fertilizers on:: Root and biomass yield of Sweet potato (Ipomoea batatas) at Delbo watershed in Wolaita, southern Ethiopia

A study was undertaken to assess the effects of combined aplication of inorganic (NP) and organic (FYM) fertilizers on root and biomass yield of Sweet potato (Ipomoea batatas (L.) Lam). The field experiment was conducted from June-Dec. 2008 at Delbo Watershed, two N levels (23 and 46 kg/ha) and two P levels (20 and 40 kg/ha) were considered as inorganic fertilizers along with one unfertilized control treatment.The findings of this study clearly showed that yield and yield components of sweet potato at Delbo watershed can be enhanced by combining FYM and inorganic fertilizers. In this study the highest yield (24.12t/ha) was achieved using 46kg/ha N and 5t/ha FYM. Accordingly, the economic analysis showed that the highest net benefit of 37,880 Birr was obtained from 46kg/ha N and 5t/ha FYM. Considering the scarcity associated with inorganic fertilizer and limited amount of FYM, 23 N kg/ha and 2.5 t/ha FYM with a net benefit of 29,635 birr, could also alternatively recommended for use by sweet potato producers in the area. Poor farmers who cannot afford fertilizer would be encouraged to use 2.5t/ha FYM.