Evaluation of bioslurry for soil fertility enhancement in Uganda
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Bioslurry (BS) is a waste product of biogas production systems. It contains plant nutrients and therefore important in improving land productivity. Large quantities of BS are being generated from various feedstocks, which are rich in nitrogen, phosphorus and potassium. Therefore, a study was carried out to (i) determine the nutrient content of BS from bio-digesters using different feedstocks; (ii) determine agronomic response of maize to liquid BS application rates, solid-separated and composted BS on maize and (iii) determine changes in nutrient concentrations in soil following application of BS. Nutrient quantities were determined from BS originating from feedstocks of cattle dung, human waste and hospital wastes. Different application rates of BS treatments used on maize based on the total N were 0, 50, 94, 125 and 156 kg N ha-1 and then an inorganic NPK (50:25:25 kg ha-1) fertilizer control. In the same study, solid suspensions of the bioslurry were separated by a fabric and composted with market wastes. The compost was compared with cattle dung, fresh bioslurry and control (with no manure). Results indicated that BS from cattle dung and cattle dung + human waste had the highest nutrient concentration of N (1.0 - 3.4 g kg-1); P (0.35 - 0.45 g kg-1) and potassium (2.0 - 7.2 g kg-1). Hospital wastes had the least nutrient contents for nitrogen, phosphorus and potassium. The bioslurry rate at 94 kg N ha-1 realised the highest maize yield (5600 kg ha-1), which was 38.5 % higher than the no input control. Results further showed that application of fresh solid BS realized significantly more maize yield than cattle manure and compost. BS also significantly increased N, P and K concentrations in the soil with the highest obtained from fresh solid BS and application rate 94 kg N ha-1. It was concluded that bioslurry was rich in nutrients that improved soil fertility and maize yield.