EFFECTS OF BLENDED NPS AND NITROGEN FERTILIZER RATES ON YIELD AND QUALITY OF HEAD CABBAGE (Brassica oleracea var. Capitata L.)AT HARAMAYA, ETHIOPIA

Cabbage (Brassica oleracea var. Capitata L.) is one of the most important vegetable crops in Ethiopia. However, the yield of the crop is low as compared to its potential yield due to low rates application of fertilizers. The use rates of fertilizer are one of the cultural practices that help to increase the productivity of the crop. Therefore, a field experiment was conducted to evaluate the effects of blended NPS and nitrogen fertilizer rates on the yield and quality of head cabbage at Rare research site of Haramaya University during the 2022 cropping season. The treatment consistedof a factorial combination of four rates of blended NPS fertilizer (0, 50 100, and 150 kg ha-1 ) and five rates of nitrogen fertilizer (0.23, 46, 69, and 92 kg ha-1 ). The experiment was laid down in a randomized complete block design with three replications using a variety Copenhagen market. Analysis of variance revealed that the application of NPS and N fertilizer significantly influenced the phenology, growth, yield component, and quality traits of cabbage plants. Head cabbage treated with the highest dose of 150 kgha-1 NPS and 92 kg ha-1 N gave a maximum score in growth, early 50% head initiation and maturity of 55 and 88.5 days, plant spread of 60.2 cm, plant height of 35.9 cm, 10.1 wrapping leaves, total head weight and head weight of 3.2 and 2.9 kg, head diameter and height of 18.7 and 17.9, marketable cabbage head yield of 62.87 t ha-1, head compactness of 0.06 and head dry matter of 8.63%. The results of the partial budget analysis showed that application of 150 kg ha-1 NPS and 92 kg ha-1 N had a net benefit of Birr 364,797 and a marketable yield of 62.8 t ha-1with marginal rate of return of 803% which is above the minimum acceptable level. Therefore, a combined application of 150 kg NPS and 92 kg N ha-1 could be considered for head cabbage production in Haramaya area and areas with similar agro ecological and soil conditions. However, since the rates used in this study were not sufficient to satisfy crop fertilizer requirements, the inclusion of higher doses of fertilizers in the future research line is suggested.