Effects of potassium fertilizer on the yield components and tuber yield of irish potato (Solanum tuberosum L.) in Wolaita zone, Southern Ethiopia

Irish potato (Solanum tuberosum L.) is cultivated for food and cash in Ethiopia. However, its productivity is limited by various constraints among which are particularly high demands of potassium (K) fertilizer for growth and development coupled with low soil fertility. Further studies need to be done to prove the emerging research evidences that Potassium (K) is becoming a limiting nutrient in some Ethiopian soils. A field experiment was conducted to determine effects of K-fertilizer (KF) on yield components (YC) and yield of potato in Abota-Ulto (Loc-1) and Gututo-Ampokosha (Loc-2) locations, Southern Ethiopia. Treatments included different rates of potassium fertilizer: 0, 30, 60, 90, 120, 150 and 180 kgha-1. The experiment was laid out in RCBD (randomized complete block design) with three replications. Results revealed that YC and yield of potato were significantly affected by both main and interaction effects of KF rates and locations. Marketable tuber yield (MTY) was significantly increased from 15.6mtha-1 in the control to 33.6mtha-1 with KF (potassium fertilizer) rate 150 kgha-1. Significantly higher MTY was obtained in Loc-1 than Loc-2. K-fertilizer rates by location interaction effects were significant on YC and yield of potato. In Loc-1 the highest MTY was obtained with KF applied at150 kgha-1 whereas in Loc-2 the highest MTY was obtained with KF applied at120 kgha-1. Results of partial budget analyses showed that in Loc-1, the highest net benefit (Ethiopian Birr 96060ha-1) with marginal rate of return was 1102% with KF applied at 150 kgha-1. In Loc-2, the highest net benefit (Ethiopian Birr 73312.8 ha-1) with marginal rate of return was 910% with KF applied at120 kgha-1. It was concluded that potato significantly responded to KF indicating insufficient amount of K content in the soils of both locations for optimum potato production. Application of potassium fertilizer is economically feasible in both locations. Key words: K- Fertilizer application, Potato production, Marketable yield, Economic feasibility, Locations