Effect of Seed Tuber Planting Depth and Nitrogen Rate on Yield and Yield Related Traits of Potato (Solanum tuberosum L.) at Haramaya and Hirna, Eastern Ethiopia

The potato (Solanum tuberosum L.) is an important cash and food security crop in the eastern highlands of Ethiopia. However, the yield of the crop is constrained by low soil fertility and poor agronomic practices. Therefore, the field experiment was conducted at the main campus of Haramaya University and at Hirna Research substation during the 2015 main cropping season. The objective of the experiments was to elucidate the effect of seed tuber planting depth and nitrogen fertiliser rate on yield-related traits and yield of the crop. The treatments consisted of four seed tuber planting depths (5, 10, 15 and 20 cm) and five rates of nitrogen (0, 46, 92, 138 and 184 kg N ha⁻¹). The experiment was laid out as a randomised complete block design with three replications. The results of the experiment at both locations revealed that the main effect of nitrogen application rate influenced total dry weight, unmarketable tuber yield, the percentage of small-sized and medium-sized tubers. Nitrogen rate and seed tuber planting depth also interacted to influence unmarketable tuber yield, the percentage of medium and large-sized tubers produced, and tuber starch content. The main effects of seed tuber planting depth significantly influenced total dry biomass, unmarketable tuber yield, total tuber yield, marketable tuber yield, the percentage of small-sized tubers produced and tuber starch content. Increasing seed tuber planting depth generally enhanced the aforementioned parameters. However, for most parameters, the highest values were obtained already at the seed tuber planting depth of 10 cm. The optimum total and marketable tuber yields of 26.93 t ha⁻¹ and 26 t ha⁻¹ for Haramaya and 34.57 t ha⁻¹ and 32.65 t ha⁻¹ for Hirna were obtained in response to planting seed tubers at the depth of 10 cm.