Integrated Application of Compost and Inorganic Fertilizers for Production of Potato (Solanum tuberosum l.) at Angacha and Kokate in Southern Ethiopia

Abstract

Declining soil fertility is one of the major problems causing yield reduction in Ethiopia. Farmers at Angacha and Kokate apply both organic and inorganic fertilizers to overcome the problem and increase yield. However, application of manure is restricted only to homestead areas due to shortage of manure to cover the out field and chemical fertilizers are costly to apply the recommended rate.  This experiment was conducted during 2005 and 2006 growing seasons at Angacha and Kokate. The objective of the experiment was to determine the optimum compost and NP fertilizers rate for potato production in the respective locations. Compost was prepared at each location with available materials in respective locations, and incorporated in to the soil 30 days before planting. Improved potato variety Tolcha was used as a test crop. Four levels of N/P (0/0, 36.7/13, 55/19.6, and 73.4/26 kg ha^-1) and four levels of compost (2.5, 5, 7.5, and 10 t ha^-1) were arranged in RCBD with factorial experiment with three replications. Nationally recommended NP rate (111 kg N and 39 kg P ha^-1) was used for comparison. Surface soil samples (0-30 cm) were analyzed for total N, available P, pH and organic matter (organic carbon). Application of compost increased tuber yield at both locations although not significantly. Application of NP increased tuber yield highly significantly (P<0.01) at both locations. The highest yield (34 t ha^-1 at Angacha and 30.54 t ha^-1 at Kokate) was obtained with application of 111 kg N and 39 kg P ha^-1 without compost at both locations with yield advantages of 11.06 t ha^-1 and 13.95 t ha^-1 at Angacha and Kokate, respectively, and this is economically significant. Application of 10 t ha^-1 compost and 73.4 kg N + 26 kg P ha^-1 gave yield advantages of 6 and 10.8 t ha^-1 at Angacha and Kokate, respectively. In conclusion, combined or sole application of compost and NP fertilizers could increase tuber yield. However, large amount of compost should be applied to significantly increase yield. Farmers in the area can apply choosing either 111 kg N + 39 kg P ha^-1 or 10 t + 73.4 kg N + 26 kg P ha^-1 depending on their interest, the availability of compost material, labor and money to purchase more fertilizers.

Key words: Compost, NP fertilizers, Combined application