Optimizing cropland management to mitigate climate-induced nitrogen leakage risk in Chinese ecosystems

CONTEXT

The balance between nitrate (NO₃⁻) and ammonium (NH₄⁺) in soils is pivotal for determining nitrogen (N) leakage risks and plant N availability. However, our understanding of how management practices and future climate change affect this balance across ecosystems remains limited.

OBJECTIVE

This study (1) quantifies the spatial variability and drivers of N leakage risk and inorganic N availability, (2) projects the impacts of future climate change, and (3) proposes management practices to mitigate these risks while sustaining adequate inorganic N supply.

METHODS

We developed Random Forest and linear mixed-effects models to analyze the spatial distribution and key drivers of the NO₃⁻ to NH₄⁺ ratio and the dissolved inorganic N to total N ratio, based on a dataset of 6592 observations from diverse ecosystems in China.

RESULTS AND CONCLUSIONS

Ecosystem-specific variations in N leakage risks ranged from conservative N cycling in wetlands (NO₃⁻/NH₄⁺ = 0.43) to leakier cycles in paddy (3.50) and upland (9.10) soils. Management practices, including mineral N input, manure application, and irrigation, exerted stronger influences on the NO₃⁻/NH₄⁺ ratio than climate, soil, and terrain factors. Projections for the 2030s–2090s under Shared Socioeconomic Pathways 5–8.5 suggest a 1.4 % to 14.7 % increase in the NO₃⁻/NH₄⁺ ratio, with the most pronounced changes in croplands of Southeast China. A combined approach of reducing mineral N fertilizers, increasing organic substitution, and optimizing irrigation could mitigate up to 62.3 % of climate-induced N leakage while maintaining sufficient inorganic N for plant growth.

SIGNIFICANCE

These findings provide valuable insights for improving N management strategies in croplands, contributing to sustainable intensification and climate adaptation efforts.