Soil texture may be more important than farm management approaches in affecting how much organic carbon is stored in sequestration schemes.
In a study on 21 conventional and 21 innovative ‘pioneer’ farms, researchers in Austria found that while most management practices such as cover crops and ensuring crop diversity did increase organic carbon capture in soil, whether a soil is coarse or fine had by far the most significant impact.
Coarse-textured soil had significantly higher organic carbon sequestration potential than medium or fine soils, the scientists noted, and while previous work has shown that fine-textured soils have higher storage capacity for organic carbon, sandy soils are more responsive to shifts towards conservation agriculture approaches.
Schemes need shaping to avoid unfairness
The work suggests that a major part of soil’s potential in climate mitigation is beyond farmers’ control — and this has potential implications for the roll-out of schemes to encourage carbon sequestration on agricultural land.
“Since differently-textured soils do display a distinct soil organic carbon saturation, storage targets and result-based carbon payment schemes need to be formulated carefully,” the researchers wrote in the journal Geoderma.
“Clearly, the fact that soil texture is a stronger predictor for soil organic carbon sequestration potentials as compared to conservation farming practices is an important finding and points to the need of texture- or soil type-specific targets when institutionalizing carbon sequestration targets.”
There is a risk of inherent unfairness in carbon farming schemes which reward carrying out soil management approaches, they said, as participants would see the same gains benefits regardless of how much carbon is actually sequestered.
“Considering carbon sequestration goals within these economic, social and political objectives and interests, we advocate for strategies harmonizing activity- and results-based approaches to maximize both effective ecological impact and wide-spread adoption of soil health innovations,” they concluded.
