The potential to mitigate global warming with no‐tillage management is only realized when practised in the long term

TLDR

No‑tillage (NT) management is promoted as a way to offset greenhouse gas emissions by sequestering soil carbon, but true mitigation requires a net reduction in global warming potential from CO₂, N₂O, and CH₄ fluxes. We compiled all available data comparing soil‑derived GHG emissions between conventional tilled (CT) and NT systems in humid and dry temperate climates. Newly converted NT systems increase GWP relative to CT, with long‑term adoption (>10 years) only significantly reducing GWP in humid climates; N₂O emissions drive this trend, underscoring the need for improved nitrogen management and revealing that NT’s mitigation potential is highly time‑dependent and variable.

Abstract

Abstract No‐tillage (NT) management has been promoted as a practice capable of offsetting greenhouse gas (GHG) emissions because of its ability to sequester carbon in soils. However, true mitigation is only possible if the overall impact of NT adoption reduces the net global warming potential (GWP) determined by fluxes of the three major biogenic GHGs (i.e. CO 2 , N 2 O, and CH 4 ). We compiled all available data of soil‐derived GHG emission comparisons between conventional tilled (CT) and NT systems for humid and dry temperate climates. Newly converted NT systems increase GWP relative to CT practices, in both humid and dry climate regimes, and longer‐term adoption (>10 years) only significantly reduces GWP in humid climates. Mean cumulative GWP over a 20‐year period is also reduced under continuous NT in dry areas, but with a high degree of uncertainty. Emissions of N 2 O drive much of the trend in net GWP, suggesting improved nitrogen management is essential to realize the full benefit from carbon storage in the soil for purposes of global warming mitigation. Our results indicate a strong time dependency in the GHG mitigation potential of NT agriculture, demonstrating that GHG mitigation by adoption of NT is much more variable and complex than previously considered, and policy plans to reduce global warming through this land management practice need further scrutiny to ensure success.