Greenhouse gas emissions during decomposition of cover crops and poultry litter with simulated tillage in 90‐day soil incubations

Summary

This 90-day controlled soil incubation study examined greenhouse gas emissions from decomposing cover crop residues (oat, turnip, Austrian winter pea) and poultry litter in an organic cotton production system, comparing soil-incorporated versus surface-applied residues to simulate conventional and no-till practices. No-till conditions produced substantially higher N₂O emissions (81.2% higher in 2020, 35.8% higher in 2021) than conventional tillage, whilst total CO₂ equivalent emissions normalised to carbon input were highest in the legume (Austrian winter pea) treatment across both years. The findings suggest that whilst no-till may build soil carbon and nitrogen stocks, the short-term climate impact through increased N₂O emissions warrants consideration in organic farming management decisions.

UK applicability

The findings are moderately applicable to UK organic farming systems, particularly for cover crop and manure management in arable operations. However, UK soil temperatures, moisture regimes, and the prevalence of different cover crop species (particularly legumes) may alter emission trajectories; field-scale validation under UK pedoclimatic conditions would strengthen applicability to UK organic practice.

Key measures

Carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) emissions (g per unit time); percentage of applied carbon and nitrogen lost as gases; CO₂ equivalents of total greenhouse gas emissions; soil methane uptake

Outcomes reported

The study measured soil CO₂, N₂O, and CH₄ emissions during 90-day decomposition of cover crop residues and poultry litter under simulated conventional tillage and no-till conditions. Results showed that 3.5% of applied carbon escaped as CO₂, 0.75% of nitrogen escaped as N₂O, with no-till producing significantly higher N₂O emissions than conventional tillage.

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