Agronomic and Yield Response of Cabbage (Brassica oleracea L. var. Capitata) to Combined Application of Bio-slurry and Inorganic Fertilizers

Background and Objective: Organic waste recycling for agriculture is an important practice that has a high potential to improve soil fertility and crop yield with little environmental cost. A sole or combined application of waste sourced bio-fertilizers are an option for sustainable crop production in the era of climate change. However, a limited and site-specific research has been reported on the combined effects of organic and inorganic fertilizers. Therefore, the current study was designed to optimize the combined rates of bio-slurry and inorganic fertilizer in order to improve agronomic performance and yield of cabbage. Materials and Methods: A field experiment was conducted to evaluate the plant growth performance and head yield of cabbage in response to combined application of bio-slurry and NP inorganic fertilizers at Hawassa in southern Ethiopia during the 2017 cropping seasons under rain-fed condition. Treatments consisting of four levels of bio-slurry (10 m, 30 m, 50 m and 70 m haG 1 ) and five levels of NP (0, 25, 50,75 and 100% of the recommended rates) were laid out in randomized complete block design with three replications. Results: The results revealed marked effect of the organic treatments on agronomy and head yield of cabbage. The interaction effects of bio-slurry and NP had significantly (p<0.05) affected plant height, number of expanded leaves, days to head initiation, days to 50% heading, days to first harvest, head height, total yield, above ground fresh and dry biomass and harvest index. Highest value of plant height, number of unfolded leaves, above ground fresh weight, above ground dry weight, head weight and total yield were recorded for the combined application of 50 m 3 bio-slurry with 75% of the recommended NP haG 1 . Treatments that received 50 m 3 bio-slurry in combination with 75% recommended nitrogen and phosphorous RNP haG 1 gave the highest marginal rate of return of 6891%, indicating that for every 1.00 birr invested for 50 m 3 bio-slurry with 75% of the RNP haG 1 of fertilizer, farmers can obtain an additional 68.91 ETB. Conclusion: Therefore, the combined application of 50 m 3 haG 1 bio-slurry with 75% RNP can be recommended for cabbage production in the research area and similar agro-ecologies.