The effect of sludge-based fertilizers on the growth performance of kale and the physicochemical property of soil.
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The use of sludge as an organic fertilizer allows for recycling of nutrients especially phosphorus, is environmentally friendly and also economically feasible playing a big role in sustainable agriculture. The study was conducted to determine the potential of three locally available sludge types in Uganda in enhancing the growth performance of Brassica oleracea var. viridis (kale). Triplicates of potted kale plants were grown in nine fresh sludge amendments; NWSC50g/kg, NWSC100g/kg, NWSC200g/kg, UBL50g/kg, UBL100/kg, UBL200g/kg, SD50g/kg, SD100g/kg, SD200g/kg alongside a positive control of NPK inorganic fertilizer and a negative control (CTRL) with unmodified soil. The study was conducted from the greenhouse in Makerere Botanical Gardens, Department of Plant Sciences, Microbiology and Biotechnology. Soil samples were taken from the amendments and their physicochemical properties were measured. The plants were monitored and at 60 days old, their shoot length, leaf length and number of leaves were determined and recorded at intervals of five days. At the end of the experiment, fresh weight of the leaves was also measured. Shoot length, leaf length and number of leaves were subjected to two-way ANOVA at P = 0.05 and linear regression analysis. Fresh weight, nitrogen, phosphorus and potassium content of the soil were analysed using one-way ANOVA at P = 0.05. Significant differences were observed in shoot length (ANOVA, P=2.2 X 10-16), leaf length (ANOVA, P=2.2 X 10-16), number of leaves (ANOVA, P=2.0 X 10-16), fresh weight (ANOVA, P= 0.00143), nitrogen (ANOVA, P=2.0 X 10-16), phosphorus (ANOVA, P=2.0 X 10-16) and potassium (ANOVA, P=4.94 X 10-15). NWSC100g/kg sludge was very effective in enhancing the yield of kale therefore it could be an effective substitute for inorganic fertilizers as an accessible, cheap and environmentally friendly organic fertilizer. To evaluate its feasibility, field experiments are recommended and farmers are encouraged to adopt the use of sludge due to its potential economic benefits.