INFLUENCE OF SEED TUBER SIZE AND PLANT SPACING ON YIELD AND QUALITY OF POTATO (Solanum tuberosum L.) IN HOLETTA, CENTRAL ETHIOPIA`

Plant spacing and seed tuber size are important agronomic management practices in the production of potato (Solanum tuberosum L.). However, potato farmers in Ethiopia often use haphazard plant spacing and tuber sizes, which contributes to the low yield of the crop. A field experiment was conducted during off season of 2014 at the research field of Holetta Research Centre, Ethiopia with the objective of elucidating the effect of varied seed tuber spacing and seed tuber sizes on the productivity of the crop. The treatments consisted of five levels of plant spacing (75 x 30 cm, 60 x 30 cm, 60 x 20 cm, 50 x 30 cm and 50 cm x 20cm)and four seed tuber sizes (25-34, 35-45, 46-55 and >56mm) using potato variety named Belete. The experiment was laid out as a randomized complete block design in a factorial arrangement and replicated three times. The results indicated that seed tuber size and plant spacing significantly (P< 0.05) influenced most of growth, yield, yield components and some tuber quality parameters of the crop. Total tuber yield and marketable tuber yield t ha-1 significantly (P< 0.05) affected by plant spacing and seed tuber size where the maximum marketable tuber yield (33.68 t ha-1) and total tuber yields (34.38 t ha-1) were obtained in response to the spacing of 60 x 30 cm and 50 x 20 cm, respectively, while highest total and marketable tuber yields of 36.16 and 37.65 t ha-1, respectively, obtained large-sized tubers (>56 mm). The widest plant spacing and the medium-size seed tubers (35-45mm) 17.06 and 16.28 t ha-1 was produced higher yield of large tuber sizes, respectively. The closest plant spacing (50 x 20 cm) and the largest-sized tubers (>56mm was produced highest yields of small and medium-sized tubers, respectively. The maximum starch yield of 8.07 t ha-1was produced from large-sized tubers (56mm) and the lowest yields of starch 5.45 t ha-1 was obtained from small-sized tubers (25-34mm).The use of medium plant spacing (60 x 30 cm) and medium-sized tubers (35- 45mm) led to the production of the highest yield of the tested potato variety. In conclusion, the study revealed that potato production could be maximized by manipulating either plant spacing and/or seed tuber sizes to be planted.