Comparative study on the effect of bio-slurry and inorganic N-fertilizer on growth and yield of kale (Brassica oleracea L.)

Kale is one of the nutritious leafy vegetables with a high nitrogen fertilizer requirement. However, soil fertility is declining progressively due to the imbalanced use of inorganic fertilizer. Discharging bio-slurry as waste will lead to environmental pollution and disposing will also lead to costs because of its large volume. Consequently, replacing chemical fertilizers with bio-slurry can not only achieve efficient resource utilization and disposal cost, but also reduce the amount of chemical fertilizer used and environmental pollution attributed by chemical fertilizers. Therefore, a pot experiment was conducted in a mesh house at Hawassa College of Agriculture to evaluate the combined effect of bio-slurry and inorganic nitrogen fertilizer for growth and yield performance of kale. Five combinations of liquid bio-slurry and inorganic nitrogen fertilizer were used, that is, 25% bio-slurry + 75% nitrogen, 50% bio-slurry + 50% nitrogen, 75% bio-slurry + 25% nitrogen, 100% bio-slurry, 100% nitrogen and 0 use of either fertilizer source as a control. Data on phenology, growth and yield attributes were recorded. Results revealed that the treatment had significant effect on growth and yield attributes of kale. The highest (455.10 g) leaf fresh weight and fresh biomass (814.86 g) was obtained when 100% sole application of liquid bio-slurry was used. Based on these results, it can be concluded that application of 100% bio-slurry can improve the production of kale in the study area.   Key words: Bio-slurry, chemical fertilizers, growth, yield attributes, kale, nitrogen.