Effects of Blended NPSB Fertilizer on Yield and Yield Related Traits of Potato (Solanum tuberosum L.) Varieties in Oda Bultum District, Eastern Ethiopia

Potato is an important food and cash crop in eastern Ethiopia including Oda Bultum District. However, there is no information on the role of blended NPSB fertilizer required to produce tuber yield and tuber quality traits. A field experiment was conducted in Oda Bultum District, under rainfed during 2018 cropping season, with the objectives of assessing the effects of blended NPSB fertilizer rates on yield-related traits and tuber yield of potato varieties and to estimate the cost-benefit of the application of blended NPSB fertilizer in potato production. The treatments consisted of two potato varieties (Bubu and Gudanie) and six rates of NPSB (0, 100, 150, 200, 250 and 300 kg NPSB ha-1) fertilizer. The experiment was laid out as a Randomized Complete Block Design in a 6 x 2 factorial arrangement and replicated three times. Analysis of variance revealed that the two main factors; blended NPSB and variety had a significant effect on all traits except that fertilizer and variety had a non-significant effect on days to 50% emergence. Interaction of blended NPSB fertilizer and variety had a significant effect on total tuber number/hill, average tuber weight, total and marketable tuber yields (t ha-1). Gudanie variety emerged, flowered and matured earlier than Bubu. Early flowering of the crop was observed in a plot which did not receive fertilizer while the application of NPSB fertilizer delayed flowering and maturity of plants that received highest rates NPSB fertilizer (200, 250 and 300 kg ha-1). The highest total tuber number hill-1 (16.00) was obtained from Gudanie variety at the application of 200 kg ha-1 NPSB fertilizer. The highest proportion of small size tubers were obtained from plots than received no fertilizer while the largest proportion of large size tubers were obtained from plots that received 200, 250 and 300 kg ha-1 NPSB fertilizer. The highest total and marketable tuber yields of 30.55 and 27.22 t ha-1, respectively were obtained from Gudanie variety with the application of 200 kg ha-1 NPSB fertilizer. Gudanie had a significantly higher specific gravity (1.085g/cm3), tuber dry matter (21.98%) and starch content (15.82%) while plants produced tubers with highest specific gravity, tuber dry matter and starch content due to the application of 200 kg ha-1 NPSB fertilizer. Moreover, the highest net benefit of 116,330.24 Birr ha-1 with 4066% marginal rate of return were obtained from growing of Gudanie variety with the application of 200 kg ha-1 NPSB plus 100 kg ha-1 urea fertilizer that could be recommended for production of potato in the study area.