Effects of bio-digestion on the quality of cattle bio-slurry and yield of radish on a Ferralsol in central Uganda
Abstract
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.