Decomposition and nutrient release patterns of municipal solid waste compost in two agro‑ecological zones of Uganda
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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
Agriculture & Food Security
Abstract
Deteriorating soil fertility is a major constraint to agricultural production and food security among
smallholder farmers in Uganda and throughout sub-Saharan Africa, where the majority of the population relies on
subsistence farming for its livelihoods.
Unfortunately, inorganic fertiliser used as a significant soil nutrient replenishment is unsustainable, causing adverse
environmental effects, including soil acidification and pollution of water bodies. Therefore, finding alternative, more
sustainable, low-cost nutrient management systems is vital. This study assessed the decomposition and nutrient
release patterns of municipal solid waste compost (MSWC) in a 36 weeks litter bag experiment under field conditions
in two agro-ecological zones (AEZs) of Uganda.
Results: We found a higher rate of decomposition in the South-western Grass Farmlands (SGF) agro-ecological
zone (0.041 week−
1, with 20% of initial compost mass remaining after 36 weeks of decay) compared to Southern
and Eastern Lake Kyoga Basin (SEKB) (0.043 week−
1, 32% of initial litter mass remaining). The half-life values were 16
and 17 weeks for SGF and SEKB AEZs, respectively. The nutrient release rates differed between the two study sites.
The macronutrient release pattern in both sites followed the order K > P > N. The secondary macronutrients release
followed the order Ca > Mg in the SGF, while in SEKB, the order was reversed. The micronutrients followed the order
Cu > Mn > Fe > Zn and Cu > Mn > Zn > Fe in SGF and SEKB AEZs, respectively. The MSWC mass loss during decomposition
was negatively correlated with rainfall in both AEZs and with temperature in SGF AEZ, while it was positively correlated
with temperature in SEKB AEZ. However, the relationship with nutrient release rates was inconsistent in both
AEZs.
Conclusions: Our results showed consistent release of nutrients in all AEZs throughout the study period, which coincides
with the two cropping seasons in Uganda, suggesting that smallholder farmers can use MSWC as a soil amendment
to address soil fertility decline and improve crop productivity. However, because most nutrients were released
almost right away in both AEZs, planting should be done at the beginning of high rainfall months when soil moisture
is high to synchronise nutrient release from MSWC with crop demand and maximise nutrient uptake by crops while
minimising losses to the environment. Furthermore, the inconsistent relationships between the climatic variables and
nutrient release suggest that other factors, such as site-specific microbial composition, influenced MSWC nutrient
release. Therefore, long-term research is needed to examine other factors affecting nutrient release in these AEZs.
Description
Keywords
Single exponential model, Microbial activity, Mass loss, Nutrient release, Synchronisation
Citation
Kabasiita, J. K., Opolot, E., Sande, E., & Malinga, G. M. (2022). Decomposition and nutrient release patterns of municipal solid waste compost in two agro-ecological zones of Uganda. Agriculture & Food Security, 11(1), 1-14. https://doi.org/10.1186/s40066-022-00392-3