Climate-Smart Slurry Management for Sustainable Crop Production in a Warming Future

The annual nitrogen (N) production from livestock manure is comparable to that of synthetic N fertilizers used globally in croplands. Despite its recognized value for crop nutrition, current inefficient manure application contributes ∼10% to global anthropogenic greenhouse gas (GHG) emissions. Addressing this challenge, we investigated semiliquid manure slurry, which in some regions provides up to half of the N supplied to crops. Using meta-analysis and machine learning methodology, we predicted agricultural and environmental impacts of slurry use in different climate scenarios based on 1952 paired observations in global field experiments. Current suboptimal uses of slurry generate 7% (0.1 Tg N) higher nitrous oxide emissions than synthetic fertilizers. Under future warming scenarios and without optimization, these emissions are projected to increase by an additional 3-5% (∼0.2 Tg N) and total noncarbon dioxide (CO₂) GHG emissions by 30% (600 Tg CO₂ equivalents year^-1). Current evidence identifies the combination of subsurface slurry application and nitrification inhibitors as an effective optimization strategy. This strategy may reduce non-CO₂ GHG emissions by 30%, equivalent to an 8% reduction in the total agricultural GHG emissions. We estimated that this optimization, combined with a favorable slurry N-to-total N ratio, has the technological potential to increase global cereal production by up to 20% and restore organic carbon stocks in topsoil by 5% (3400 Tg carbon). Thus, optimizing slurry use should be a priority, as it contributes to climate change mitigation, food security, and soil fertility.