A new study has challenged the carbon reduction assumptions of conservation agriculture.
A Rothamsted-led study suggests that regen agriculture’s impact on greenhouse gas emissions is more complex than previously thought. While some principles of conservation agriculture consistently reduce emissions, others can increase them depending on environmental conditions and management decisions.
The research analysed 422 scientific studies from around the world to assess how key conservation agriculture principles (reduced/no tillage, mulching, crop rotations) and appropriate fertiliser management influence emissions of the three major greenhouse gases: carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄).
The findings revealed that the climate benefits of conservation agriculture depend not only on which principles of conservation agriculture are adopted, but also on how they are implemented and the environments in which they are used.
Reduced tillage shows the strongest climate benefits
Among the principles of conservation agriculture examined, reduced tillage and zero tillage showed the most consistent potential for reducing greenhouse gas emissions, including nitrous oxide emissions
By reducing soil disturbance, these practices help protect soil structure and slow the release of carbon stored in soils. Researchers also found some evidence that it enhances soil uptake of methane
The study also examined mulching, including the retention of crop residues and the use of cover crops. While mulching provides well-established benefits for soil protection, water retention and soil health, the review found evidence that it can increase greenhouse gas emissions in some farming systems.
It found that decomposing organic materials can create conditions that stimulate microbial activity, increasing the production of carbon dioxide, nitrous oxide and methane. The findings highlight the need for careful consideration of mulch type, quantity and management when designing climate-smart agricultural systems.
Fertiliser results vary
The study found highly variable results with fertiliser management strategies, including organic amendments, integrated soil fertility management, use of slow-release fertilisers and nitrogen-use efficiency approaches.
Some strategies reduced emissions while others increased them depending on environmental conditions. “Approaches promoting the appropriate use of fertiliser, as the fourth proposed principle of conservation agriculture, showed mixed effects on greenhouse gas emissions.
“This shows that environmental factors like rainfall and soil type create complex challenges for reducing emissions in temperate and tropical farming systems,” said Dr Grace Kangara, lead author of the study and researcher at Rothamsted Research.
The researchers found that nitrogen application rate remains a key driver of nitrous oxide emissions, reinforcing the importance of precision nutrient management.
Role of crop diversity
The analysis also explored the influence of crop rotations on greenhouse gas emissions.
Systems that included legume crops tended to be associated with lower carbon dioxide emissions than continuous cereal-based rotations, while cereal-after-cereal systems were more often linked to increased emissions.
These findings add to growing evidence that diversified cropping systems can support environmental sustainability while reducing reliance on synthetic fertilisers.
The authors concluded that critical knowledge gaps need filling and that greater investment in long-term field experiments and more standardised reporting of greenhouse gas measurements is required. Rather than viewing conservation agriculture as a single climate solution, the researchers argue that individual practices must be evaluated separately and in combination, with local environmental conditions taken into account.
