Manure management in African smallholder farms affects greenhouse gas emissions and leachate losses

In sub-Saharan Africa, cattle manure is a critical yet undervalued bioresource, typically stored in uncovered heaps prior to land application, resulting in substantial greenhouse gas (GHG) emissions and nitrogen (N) losses. We quantified N losses and GHG emissions from six manure management treatments: uncovered and covered manure, interacted with or without straw or charcoal amendments. Covered manure treatments were sheltered with small roofs made of opaque polyethylene installed 10 cm above the container, while the uncovered treatments remained open. Aliquots of 200 kg solid cattle manure were incubated outdoors in open containers to simulate representative storage conditions. While charcoal addition reduced CH$_4$ emissions, it did not affect N$_2$O. Conversely, straw-amended treatments emitted approximately twice as much N$_2$O as unamended manure, with no significant effect of covering. Site-specific $^{15}$N-N$_2$O analysis provided evidence that denitrification dominated N$_2$O production, with 85–95% of N$_2$O reduced to N$_2$. Emission factors ranged between 2.1 and 4.8% for N$_2$O and 18.6-68.0 g CH$_4$ kg$^{−1}$ volatile solids, significantly exceeding IPCC default values, highlighting a critical gap in regional emission inventories. Overall, while straw amendment resulted in the greatest N losses, covering was an effective, low-cost and scalable option to preserve nutrients for sustainable crop production.