Optimizing fertilization rate can maintain the greenhouse gas mitigation effect of no-tillage: A global-scale meta-analysis

Abstract

Context

No-tillage (NT) is an important agricultural practice for mitigating global warming and the trade-offs between the environment and food security. However, it remains unclear how different management practices affect and regulate greenhouse gas (GHG) emissions and yields in NT systems.

Objective

We integrated 99 published publications from around the world to construct a dataset of 517 paired observations to assess the impact of different management practices on GHG emissions and yields of NT systems, and to identify optimal management practices.

Methods

Hierarchical nested models were used to more accurately quantify the effects of management practices on GHG emissions and yields in NT systems. Subgroup meta-analyses, mixed-effects meta-regression and weighted random forest analysis were used to explore the relationships between climate, crop type, soil texture, straw and fertiliser type, and GHG emissions and yields.

Results and conclusions

Fertilization (22 % and 117 %), straw return (19 % and 16 %), and the interaction between fertilization and straw return (59 % and 225 %) significantly increased CO₂ and N₂O emissions in NT systems, but had no effect on CH₄ emissions. Fertilization (30 %) and interaction between fertilization and straw return (94 %) significantly enhanced yield in NT systems, while straw return did not affect yield. GHG emissions were not significant at low straw return rates (≤ 4t·hm²). Under fertilization, organic fertilizers were more favourable than chemical fertilizers for reducing GHG emissions. In addition, dry and cold climate and soils with low silt (%) and high sand (%) content were more favourable for reducing CO₂ and N₂O emissions in NT systems. The meta-random forest showed that fertilization rate is the key factor in regulating CO₂ and N₂O emissions in NT systems. Low fertilization rate (nitrogen ≤ 140 kg·hm⁻², phosphorus ≤ 40 kg·hm⁻², potassium ≤ 50 kg·hm⁻²) maximized the maintenance the GHG mitigation effect of NT and increase yields by about 15 % compared to NT alone. The study highlighted the importance of optimising fertilization rates as the key to maintain the GHG mitigation effect and crop yield of NT.

Implications or significance

These findings will help optimise management practices in NT systems to reduce GHG emissions and create a win-win situation for the environment and food security.