Spatial variability of mineral surface area and carbon sequestration potential at the farm scale – a case study

Context

The ability of soils to contribute to greenhouse gas mitigation requires the stock of carbon to be increased in the long term. Studies have demonstrated the potential of soils to increase in carbon at global to regional scales, with soil mineral surface area a key factor to this potential. However, there is limited knowledge on the distribution of mineral surface area and whether the distribution of soil carbon sequestration potential varies at the farm scale.

Aims

The aim of this study was to evaluate the spatial variability in mineral surface area and sequestration potential of SOC at a farm scale.

Methods

We used a case study farm to apply existing published methodology and assess the spatial distribution of the mineral surface area, the maximum amount of stable carbon that a soil could hold, and the subsequent potential for soil carbon sequestration at the farm scale. A total of 200 samples were collected across the farm using a balance accepted sampling design prior to analysis for total carbon, mineral surface area, and sequestration potential.

Key results

Despite being in a localised area, the farm demonstrated that the distributions of mineral surface area and total carbon were related to variation in the underlying soil type. When data were examined spatially, there were areas within the farm that had greater potential to stabilise more carbon and also regions where there were greater carbon stocks.

Conclusions

The spatial distribution of SOC, mineral surface area, and potential to increase MAOC was well represented by the spatial distribution of soil type within a farm. This case study demonstrated areas within the farm that had potential to increase the MAOC fraction.

Implications

This case study offers an approach that would give farmers and land managers knowledge to improve the understanding of the carbon dynamics across their farm and to identify areas that have greater potential to contribute to greenhouse gas mitigation and the areas that would be more susceptible to soil carbon loss. Using this approach could allow targeted management practices to be applied to specific regions on-farm to either increase soil carbon or protect existing stocks.