EFFECT OF BLENDED NPS AND ZINC FERTILIZER RATES ON GROWTH, YIELD, YIELD COMPONENTS AND QUALITY OF POTATO (Solanum tuberosum L.) AT DEBRE BERHAN, NORTH SHEWA, ETHIOPIA

Abstract

Potato (Solanum tuberosum L.) is an important leading tuber crop for food and nutrition security as well as cash crop for smallholder farmers in Ethiopia. However, the yield of the crop is low at national as well as regional level due several factors such as inappropriate agronomic practices, disease and pests, lack of good quality seeds among which low soil fertility and poor fertilizer management practice applied by growers. A field experiment was carried out during the main cropping season at Debre Berhan University College of agriculture and natural resource science research site. The field experiment was conducted with the objective of evaluating the effects of NPS fertilizer and zinc on the growth, yield, yield components and quality of potato. The treatments consisted of four levels of NPS (0, 90, 180 and 270 kg ha-1) fertilizer and four levels of zinc (0, 225, 450 and 675 ppm) and an improved potato variety called ‘Belete’ was used as a test crop. The experiment was laid down in a Randomized Complete Block Design (RCBD) in a 4x4 factorial arrangement and replicated three times. Results of the experiment indicated that the main effects of NPS and zinc fertilizers as well as the interaction effects significantly affected plant height, main stem number, number of branch, average tuber weight, marketable tuber number per hill, total tuber number per hill, marketable tuber yield (t ha-1), total tuber yield (t ha-1), tuber dry matter, specific gravity and tuber starch content. The highest marketable tuber yield (42.45 t ha-1) and total tuber yield (46.06 t ha-1) were obtained from the application of 180 kg ha-1 NPS and 450 ppm zinc. The combined application of NPS and zinc fertilizer at the rate of 180 kg ha-1 NPS and 450 ppm zinc increased marketable tuber yield by 161.71% and total tuber yield by 110.22% over the control treatment. On the other hand, the lowest marketable tuber yield (16.22 t ha-1) and total tuber yield (21.91 t ha-1) was recorded from the control treatment. The combined application of 180 kg ha-1 NPS and 450 ppm Zn fertilizer level gave the maximum net benefit (Birr 1,122,300 ha-1) with an acceptable marginal rate of return (3304.35%). Hence, for economical potato production in the study area and similar agro-ecologies, it is advisable to apply 180 kg NPS ha-1and 450 ppm Zn fertilizer.