Greenhouse gas emissions from agricultural soils amended with livestock-derived facultative heap compost

Although facultative heap compost is commonly used as an organic amendment to improve soil quality and plant growth, its effect on greenhouse gas (GHG) emissions remains largely unexplored. This study aimed to evaluate the influence of different facultative heap composts on nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions from two Vietnamese soil types: sandy clay loam and loamy sand. The soils were amended with 2% (w/w) of three compost types: immature cow manure compost (C-1 M, 1 month), mature cow manure compost (C-7 M, 7 months), and poultry manure compost (P-9 M, 9 months). All treatments were adjusted to 60% water holding capacity (WHC) and incubated under aerobic conditions at 30°C for 56 days. Gas emissions were measured on days 0, 3, 7, 14, 21, 35, and 56. Results showed that N2O and CO2 emissions were significantly higher in loamy sand soil than in sandy clay loam (p < 0.05), likely due to higher total carbon (TC), total nitrogen (TN), mineral N content, and a lower C/N ratio. Application of P-9 M and C-7 M significantly increased N2O emissions in loamy sand soil, while no compost effect was observed in sandy clay loam. In both soils, the highest CO2 emissions were found in the C-1 M treatment, whereas cumulative CO2 emissions did not differ significantly between C-7 M, P-9 M, and the control. CH4 emissions were greater in sandy clay loam, likely due to its higher C/N ratio and clay content. These findings highlight the combined role of compost maturity and soil properties in regulating GHG emissions.