Exploring Desert Locust (S. gregaria) Frass as an Organic Fertilizer for the Growth of Kales (Brassica oleracea L.) under Open Field Conditions

Abstract

In Kenya, kale (Brassica oleracea L.) is one of the most commonly consumed vegetable crops, however, their yield has been decreasing due to poor soils. An experiment was conducted to investigate the growth performance, yield, chlorophyll content and nutritional quality of kales when planted using decomposed desert locust frass, chicken manure and NPK fertilizers under open field conditions.  The experimental design was a randomized complete block design with six treatments namely; A: Plain soil that had no fertilizer (negative control), B: Soil + NPK (10g per planting), C: Soil + chicken manure (2:1), D: Soil +50 g of frass, E: Soil +100 g of frass and F: Soil +150g of frass. Chemical characteristics of organic manures showed that decomposed locust frass had significantly high levels of Phosphorus, Nitrogen, Calcium, Carbon, potassium, sodium, and Magnesium compared to decomposed chicken manure. Data were analyzed in STATGRAPHICS centurion XVI and one-way ANOVA was used to analyze for significant differences in means. Results of the growth performance of kales showed that soil treated with 100 g decomposed frass produced kale plants with a significantly (p< 0.05) higher number of leaves than kale plants grown using other fertilizer treatments in the experiment. Kales planted with chicken manure were significantly taller than kales from other fertilizer treatments. Kale leaf chlorophyll content from soil treated with 100 g decomposed frass registered the highest chlorophyll content which was significantly different (p<0.05) from chlorophyll content on kales grown using chicken manure, NPK fertilizer, and 50g and 150 g decomposed frass manure. The proximate composition analysis on harvested kale leaves showed that kales planted using 50 g decomposed locust frass had higher nitrogen, phosphorous, and crude fats concentrations compared to kales from other fertilizer treatments. These results shows that decomposed desert locusts frass has the potential to be used as an organic fertilizer in cropping system.