How scale affects N2O emissions in heterogeneous fields of a diversified agricultural landscape

Abstract

Nitrous oxide (N2O) emissions from agricultural soils vary due to factors such as soil organic matter, soil moisture, and crop type, leading to short-term variations and concentrated zones of high emissions, known as “hot moments” and “hotspots.” These peaks, occurring at various scales, contribute significantly to total N2O emissions. This is particularly relevant for sandy soils, where high porosity and low water-holding capacity promote gas diffusion and create moisture variability, leading to highly heterogeneous N2O emissions. We investigated N2O fluxes along a transect in six agriculturally used patches (0.52 ha) with varying texture, yield potential and crop rotation. We measured N2O fluxes bi-weekly over 2 years, using a non-flow-through non-steady-state (NFT-NSS) manual closed chamber system, covering different crops and weather conditions. Hot moments accounted for 6–71% of total crop N2O emissions and were mostly driven by soil physical properties. On a small scale, soil texture and environment determined spatial heterogeneity of N2O emissions being more pronounced for sandier soils. On patch level, N2O emissions differed more strongly than on microplot level and were mainly driven by crop-type and management. Our findings highlight the importance of accounting for intrinsic variability in soil texture, topography, and microclimate within patches. Additionally, broader differences across management-influenced patches must be considered to better understand the drivers of N2O emissions. This dual-scale approach emphasizes the need for high-resolution soil monitoring for mitigation strategies and to refine models. At the same time, it guides farmers toward soil-specific fertilization to reduce emissions and maintain yields in diverse agricultural landscapes.

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