effect of applying integrated mineral and organic fertilizers on seed yield, yield components and seed oil content of black cumin in central highlands of ethiopia

Black cumin (nigella sativa l.) is an important spice crop in ethiopia. however, the yield of the crop is low due to low soil fertility and poor soil fertility management practices. here, a field research was conducted to evaluate the effects of applying mineral and organic fertilizers on seed yield and oil content of black cumin. the treatment consisted of three rates of combined nitrogen and phosphorus (np) fertilizer (20/15, 40/30, 60/45 kg n/p2o5 ha-1), three rates of blended mineral nitrogen, phosphorus, sulfur and boron (npsb) fertilizers (0, 50 and 100 kg npsb ha–1), and three rates of vermicompost (vc) (0, 3 and 6 t ha–1). the experiment was laid out as a randomized complete block design in a factorial arrangement with three replications. the results showed that the interaction of mineral fertilizers and vc significantly (p < 0.05) influenced seed yield and seed oil content. increasing rates of the three fertilizers increased seed yield, but reduced the seed oil content. we concluded that applying 60/45 kg n/p2o5, 100 kg npsb, and 3 t ha–1 of vc resulted in optimum seed yield (2.1 t ha–1), which is twice as much as the average yield of the crop in the country. however, the highest seed oil content (39.70%) was recorded at the rates of minimum n/p2o5 and zero rates of both npsb and vc. this implies that integrated application of mineral and organic fertilizers can double productivity of the crop and improve farmers’ income in the study area.