Abay Ayalew and Sheleme Beyene
An experiment was conducted at Angacha Research Station in Kembata Tembaro Zone of SNNPRS to characterize the soils of the research station and evaluate the response of potato (Solanum tuberosum L.) to potassium fertilizer. A pedon with 2 m x 2 m x 1.5 m volume was opened and horizons were described in situ. Samples were collected from all identified horizons for laboratory analysis. Increasing rates of K (0, 40, 80, 120, 160, 200, 240, 280, and 320 kg ha-1 as KCl) in RCBD with four replications were used in the experiment. Recommended rates of N and P, 111 and 39.3 kg ha-1, respectively were applied to all treatments. Urea (46-0-0) and DAP (18-46- 0) were used as sources of N and P. N was applied in split at planting and after tuber initiation (as side dressing). The physico-chemical characteristics of the soil showed that the soil has good soil fertility status but organic carbon (OC) content was medium (1.56%). The soil type of the research station was identified to be Alfisols. Organic carbon (OC), total N, and K contents of the soil, ranging between 0.5 and 1.56%, 0.06 and 0.25%, and 0.19 and 0.37 Cmol (+) kg-1, respectively, and decrease with depth, whereas the available P content is the same (40 ppm) throughout the horizons. The composite soil sample contains moderate organic carbon (1.6%), whereas the total N (0.26%), available P and K contents are high. The potato tuber yield ranged between 43.97 t ha-1 at application of 200 kg K ha-1 and 53.33 t ha-1 at application of 280 kg K ha-1. Application of K did not significantly influence potato tuber yield, N, P and K concentrations both in leaf and tuber, exchangeable and available potassium in the soil. However, a yield advantage of 11.4% (5.47 t ha-1) was obtained from the application of 280 kg K ha-1 over the control, although the difference is not statistically significant. These parameters neither showed increasing or decreasing pattern with increased K application. Therefore, it is concluded that soil fertility management practices based on the findings should focus on maintaining and increasing OC content of the soil and monitoring for balances among nutrients. Based on the current finding, application of K for potato at Angacha is not required. However, since the experiment is conducted only for one year, it should be repeated to draw a sound conclusion. Besides, as potato is highly K demanding crop, periodic checking of the K status of the soil and crop response to it is important.
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