Evaluation of the Potential for Soil Organic Carbon Content Monitoring With Farmers

Abstract

Increasing soil organic carbon (SOC) content is crucial for soil quality and climate change mitigation. SOC monitoring is indispensable to the corresponding policies and should provide results at farm scale to allow for incentives. In Switzerland, farmers perform mandatory analyses of the SOC content of the 0-20 cm topsoil of every field, based on a composite sample, at least every 10 years. The corresponding results are stored in a database in canton of Geneva. These data may be relevant for topsoil SOC monitoring, in particular for carbon sequestration policies, provided that they show appropriate quality, which is analyzed in this study. The minimum detectable change (MDC) of past results calculated based on the observed SOC changes was 0.013% g g −1 at canton scale (2,700 fields). Based on extended sampling of three representative fields, different sampling strategies were simulated to determine the best future sampling guidelines for farmers. Collecting 20 aliquots with a gouge on the field diagonals was considered the best sampling compromise with field MDC of ∼0.1% g g −1 and a sampling duration of 20 min. Compared to this procedure, former farmers' sampling was not biased in average but showed a variance of 0.22% g g −1 due to smaller number of aliquots and varying sampling depths. Based on the best sampling results and assumptions on farm-scale SOC variance or SOC differences, the MDCs at farm scale ranged from 0.21 to 0.12% g g −1 (5 fields) and 0.09 to 0.05% g g −1 (30 fields), respectively. These MDCs are small compared to published monitoring networks MDCs and allow determining SOC change rates at farm scale, thus offering perspectives for inexpensive and efficient monitoring in the frame of soil quality or climate mitigation incentives. For the latter, however, additional information with equivalent soil mass and deeper-layer carbon content would be necessary.

Soil assessment in Denmark: Towards soil functional mapping and beyond

“…At a finer scale, the temporal changes in the spatial distribution of erosional and depositional processes have been examined and related to the temporal SOC changes during a 16-year period (1998-2014) to elucidate controlling factors on SOC patterns in Danish cultivated soils (128). These attempts to understand the SOC content at various scales have revealed a knowledge gap related to the linking of SOC changes over time with designing environmental and agronomical strategies to foster C storage in soils (129,130).…”

On-Farm Relationships Between Agricultural Practices and Annual Changes in Organic Carbon Content at a Regional Scale

“…To receive ecological subsidies, Swiss farmers are required to analyze a topsoil (0-20 cm) composite sample from each of their field in a certified laboratory at least every 10 years. This sampling method was assessed as an unbiased and reliable method to determine SOC annual change rates at farm scale (Deluz et al, 2020). The corresponding database contains more than 35′000 soil analyses from 1993 to present and was used by Dupla et al (2021) to determine the regional SOC annual change rate distribution and its change with time.…”

“…The selected fields were sampled at the beginning and the end of the 10-years interval by collecting 15 to 20 aliquots along the field diagonals at 0-20 cm depth to obtain a composite sample (Deluz et al, 2020). SOC and clay contents (wt%) were analyzed using Walkley-Black (Nelson and Sommers, 1983) and pipette methods (Jennings et al, 1922;Robinson, 1922), respectively.…”

The Application of an Improved Fuzzy Comprehensive Evaluation in Coal Quality Rating: The Case Study of China

“…Their results show that the overall level of the water resource-carrying capacity of Puhe River is at the critical status between overload and suitable load; the improving space is limited. Many works of literature simply used super-standard multiple methods when calculating the weight of various evaluation factors (see Zheng et al, 2019;Simpson et al, 2019;Deluz et al, 2020;Sheng et al, 2021, for example). Such fuzzy comprehensive evaluation only considers the concentration of coal resource quality analysis index but ignores the overbid index of the influence of the quality analysis index on coal quality.…”