Abstract

Field experiments were conducted at Wa (Guinea savanna agro-ecological zone) and Mampong-Ashanti (forest-savanna transition agro-ecological zone) in 2007 and 2008 to determine the growth and yield response of sweet potato (Ipomoea batatas L.) to chicken manure, inorganic fertilizer (NPK, 15-15-15) and combinations thereof. The experimental design used was a randomized complete block design (RCBD) with four replicates. The treatments were: (i) sole NPK (15-15-15) fertilizer (IF) (200 kg NPK ha^-1); (ii) sole chicken manure (CM) (6 t CM ha^-1); (iii) 150 kg NPK ha^-1 + 1.5 t CM ha^-1; (iv) 100 kg NPK ha^-1 + 3.0 t CM ha^-1 (v) 50 kg NPK ha^-1 + 4.5t CM ha^-1); and (vi) no fertilizer (control). The sweet potato variety “Okumkom” was used in both years. On the average, all the amended treatments accumulated higher plant dry matter over the growing period than the unamended or control treatment at both locations. Plant dry matter accumulation produced at Mampong-Ashanti was higher than at Wa. The highest marketable root yields of 21.4 and 23.0 t ha^-1 were obtained from combinations of 150 kg NPK ha^-1 + 1.5 t CM ha^-1 and 100 kg NPK ha^-1 + 3.0 t CM ha^-1 at Wa and Mampong-Ashanti, respectively. Integrated combinations of 150 kg NPK ha^-1 + 1.5 t CM/ha and 100 kg NPK ha^-1 + 3.0 t CM/ha are recommended for the Guinea savanna and forest-savanna transition zones, respectively, and similar representative environments to maximize yields and reduce cost on applied soil nutrient inputs. 

Key words: Integrated application, sweet potato, chicken manure, inorganic fertilizer, growth.