Effects of bio-digestion on the quality of cattle bio-slurry and yield of radish on a Ferralsol in central Uganda
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Amending Uganda’s poor soils with fertillisers is a necessity to improve crop production. Nevertheless, to attain high yields, one has to use the right rate and type of ferilisers to meet the crop nutrients because too much or too little leads to nutrient toxicity and deficiency, respectively in plants. Over reliance on mineral fertilisers has led to soil and water pollution whereby even their higher prices and unavailability on market has hindered their popularity. This study was conducted to explore cheaper alternatives to synthetic fertilisers like farmyard manure, poultry manure, green manure, bio-fertilisers, and bio-slurry. An organic fertiliser like bio-slurry undergoes bio-digestion that could have an effect on its resultant nutrient concentration and thus the resultant crop yields. A pot experiment was conducted to evaluate the effects of biodigestion on the quality of cattle bio-slurry and effect of the bio-slurry on yield of radish. The experiment was conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK) in a Completely Randomised Design (CRD). The soil used was a Ferralsol in type with a sandy clay textural class, low pH, organic matter, P and N values whereas potassium was found to be moderate. The experimental layout had 5 treatments (T1=Control; T2=fresh cattle manure substrate @ 300g; T3=fresh cattle manure bio-slurry @ 300ml; T4=sundried cattle bioslurry @ 300g and T4= NPK @1.25g) and 6 replicates. Before applying the treatments into the soil, a lab analysis was carried out on fresh cattle manure substrate, fresh bio-slurry and sundried bio-slurry to quantify their nutrient values. There was a strongly significant (P<0.001) effect of treatment on all the chemical properties (pH, Total N, total P, K and calcium) investigated with fresh bio-slurry showing high nutrient content and a neutral pH (7.2±0.02). On sampling the radish growth parameters after harvesting, it was found that there was a significant (P<0.001) effect of treatment on all the growth parameters (plant height, No. of leaves, tuber height, tuber diameter, weight of leaves, tuber weight and total biomass) investigated. On analysis, fresh bioslurry resulted in the highest average radish plant height (40.4±0.23cm), highest number of leaves (25.0±0.64), largest root diameter (13.5±0.179), longest radish tuber (32.7±0.30cm), highest weight of leaves (151.3±1.22g), tubers (288.7±0.45g) and total biomass (440.0±0.858g) per plant. On comparison to NPK, there was no significant (P>0.05) difference between the findings and fresh cattle manure substrate while the significance difference (P>0.005) was low in sundried bio-slurry and high in fresh bio-slurry. For example, fresh bio-slurry showed a 9% increase in total biomass with a 0.08% increase in sundried bio-slurry with respect to NPK. Equally enough there was 10.95% increase in tuber weight in fresh bio-slurry and 3.69% tuber increase in sundried bio-slurry compared to those from the NPK pots.