Potato yield enhancement by combined use of NPS blended fertilizer and coffee husk biochar and its economic analysis

Potato (Solanum tuberosum L.) is an important tuber crop in Ethiopia, however its yield is far below the potential yield due to different constraints, soil fertility being main among them. Therefore, a study was conducted at Masha district, southwestern Ethiopia to find out the optimum combination of NPS blended fertilizer and coffee husk biochar (organic source) for the best economic yield and quality of potato. The treatment consisted of four levels of NPS (0, 121, 242, 363 kg ha(-1)) and four levels of coffee husk biochar (0, 4, 8, 12 t ha(-1)). The experiment was arranged in randomized complete block design with three replications. Results revealed that the combined application of NPS and biochar significantly (p<0.05) influenced almost all parameters except average tuber weight, large sized-tuber number, unmarketable tuber number and yield. The highest mean values of days to 50% flowering (75 days), days to 90% physiological maturity (105 days), plant height (98 cm) and the main stem number (10 hill(-1)) were recorded from the treatment which received 363 kg NPS ha-1 + 12 t coffee husk biochar ha(-1). Also, the highest marketable tuber number (14.8 hill(-1)) and total tuber number (16.2 hill(-1)) were recorded under the treatment receiving combined application of 363 kg NPS ha(-1) blended fertilizer with 4 t biochar ha(-1). The combined application of 363 kg NPS ha- 1 + 8 t coffee husk biochar ha(-1) produced the highest marketable tuber yield of 47.8 t ha(-1) and the highest total tuber yield of 49.5 t ha(-1). The tuber specific gravity of 1.098 g cm(-3) and dry matter content of 41.4% were recorded from the treatment which received 363 kg NPS ha(-1) + 12 t coffee husk biochar ha(-1). The proportion of small-sized tuber number (55%) recorded from control treatment and medium-sized tuber number (53.3%) were recorded under treatment consisting of combined application of 363 kg NPS ha(-1) + 8 t ha(-1) coffee husk biochar. Based on partial budget analysis the combined application of 363 kg NPS ha(-1) with 8 t biochar ha(-1) gave an optimum net return of 287112 ETB ha(-1) (ETB 1= USD 0.03) and 3820% MRR (marginal rate of return). Summarily, the combined use of NPS with coffee husk biochar significantly increased potato growth, yield and physical quality.