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.

中文翻译：

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与农民一起评估土壤有机碳含量监测的潜力

增加土壤有机碳 (SOC) 含量对于土壤质量和减缓气候变化至关重要。SOC 监测对于相应的政策是必不可少的，并且应该在农场规模上提供结果以允许激励。在瑞士，农民至少每 10 年根据复合样本对每个田地 0-20 厘米表土的 SOC 含量进行强制性分析。相应的结果存储在日内瓦州的数据库中。这些数据可能与表土 SOC 监测相关，尤其是碳封存政策，前提是它们显示出适当的质量，本研究对此进行了分析。根据观察到的 SOC 变化计算的过去结果的最小可检测变化 (MDC) 为 0.013% gg–1，在州范围内（2,700 场）。基于对三个代表性领域的扩展抽样，模拟了不同的抽样策略，以确定未来农民的最佳抽样指南。在现场对角线上用凿子收集 20 等分试样被认为是最好的采样折衷方案，现场 MDC 约为 0.1% gg-1，采样持续时间为 20 分钟。与此程序相比，前农民的抽样平均没有偏差，但由于等分试样数量较少和抽样深度不同，显示出 0.22% gg-1 的方差。基于对农场规模 SOC 方差或 SOC 差异的最佳抽样结果和假设，农场规模的 MDC 范围分别为 0.21 至 0.12% gg–1（5 个田地）和 0.09 至 0.05% gg–1（30 个田地） . 与已发布的监测网络 MDC 相比，这些 MDC 较小，并且可以确定农场规模的 SOC 变化率，从而为在土壤质量或气候缓解激励措施框架内进行廉价而有效的监测提供了前景。然而，对于后者，需要具有等效土壤质量和更深层碳含量的附加信息。