Effects of Plant Spacing and Time of Harvesting on Yield and Tuber Size Distribution of Potato (<i>Solanum tuberosum</i> L) Variety Southeast Ethiopia

Abstract

Potato is one of the most important crops in the farming system of Bekoji and Kofele in the cool highlands of Arsi where potato is usually grown biennially during the main and ‘bulg’ seasons. ‘Belete’ has been the dominant potato variety in these areas for the last ten years now and farmers prefer to grow this variety for its high productivity and resistance to late blight disease. Nevertheless, farmers have complaints on its big sized tubers, considered as unmarketable, which costs them more seed to cover a given area of land and less suitable for cooking. Besides, farmers often use random population density and time of harvesting, which also contribute to this problem. The present study was therefore intended to manage the tubers’ size distribution of this variety without negatively affecting the yield of the crop through modifying plant spacing and time of harvesting from previously recommended practices. Twelve combinations of four plant spacing and three time of harvesting were studied on variety “Belete’ at Bekoji and Kofele in the main seasons of 2018 and 2019. The experiment was laid out in a completely randomized block design with 4x3 factorial arrangement in three replications. The analysis of variance revealed that the interaction effect of spacing and time of harvesting significantly (p<0.001) affected the marketable tuber yields. The narrow spacing (60cmx20cm) or high population treatment (83,333 plants/ha) with 120 days after planting resulted in the highest marketable and total tuber yield compared to the rest. While the least yields were recorded from the wider spacing of 75cmx30cm (44,444plants/ha) and early harvesting (90 days). The spacing 60cmx20cm did 17.2% increment in marketable yield over the previously recommended spacing of potato (75cmx30cm, 44,444plants/ha). From this study, therefore, it can be recommended for Belete that the narrow spacing of 60cmx20cm and harvesting at 120 days after planting could be the optimum spacing and time of harvesting to produce marketable tubers.