Abstract:
Composting is an effective method to recycle biodegradable waste as soil amendment in smallholder
farming systems. Although all essential plant nutrients are found in compost, a substantial amount of
nitrogen is lost during composting. This study therefore investigated the potential of reducing N losses
by (i) delaying the addition of nitrogen-rich substrates (i.e. poultry manure), and (ii) reducing the turning
frequency during composting. Furthermore, we tested the effect of compost application method on nitrogen mineralization. Sugarcane-waste was composted for 54 days with addition of poultry manure at the
beginning (i.e. early addition) or after 21 days of composting (delayed addition). The compost pile was
then turned either every three or nine days. Composts were subsequently applied to soil as (i) homogeneously mixed, or (ii) stratified, and incubated for 28 days to test the effect of compost application on
nitrogen mineralization. The results showed that delayed addition of poultry manure reduced total nitrogen loss by 33% and increased mineral nitrogen content by >200% compared with early addition.
Similarly, less frequent turning reduced total N loss by 12% compared with frequent turning. Stratified
placement of compost did not enhance N mineralization compared to a homogeneous mixing. Our results
suggested that simple modifications of the composting process (i.e. delayed addition and/or turning frequency) could significantly reduce N losses and improve the plant-nutritional value of compost
