Abstract:
Due to the intensification of agricultural lands, soil fertility has declined to result in
decreased land productivity. Hence, farmers excessively use expensive chemical
fertilizers that have reported deleterious effects on the environment and human health.
Co-compost of municipal solid wastes and dewatered fecal sludge has a high potential as
an agricultural resource in Sri Lanka. Biochar, a soil amendment that has been proven to
have many positive effects in improving long-term soil quality and increasing crop yield
especially with soil conditioner and organic fertilizer. This study was focused on the
residual fertilizer effect of municipal solid wastes co-compost with dewatered fecal
sludge supplemented with biochar in sandy loam soil using Ipomoea aquatic. The field
experiment was carried out at the Centre of Excellence for Organic Agriculture,
Makandura. To assess the residual fertilizer effect, Ipomea aquatica was cultivated as a
follow-up crop in a previously maize cultivated field fertilized with pelletized forms of
different co-composts combinations with biochar and mineral fertilizer. Department of
agriculture recommended chemical fertilizer was used as a control treatment. Randomized
completely block design with four blocks and eight treatments was used. Plant survival
rate, leaf area index, and plant height were measured as plant growth and yield data and
were recorded 3 times until 15 weeks. Significantly (p = 0.05) higher residual fertilizer
effect on yield could be obtained with biochar mixed municipal solid waste-dewatered
fecal sludge co-compost pellets treatments (0.86 kg m-2
) compared to the mineral
fertilizer treatments recommended by the department of agriculture (1.45 kg m-2
). It can
be concluded that municipal solid wastes with dewatered fecal sludge supplemented with
biochar can provide a significant amount of residual nutrients in long term and the
residual benefits depend on the initial nutrient composition of applied manure.
Keywords: Biochar, Co-compost, Ipomoea aquatica, Municipal solid waste, Residual
effect
