The “4 per 1,000” initiative calls for land management practices that increase soil organic C (SOC). Despite an imperative for accurate SOC measurement, several methodological issues may complicate the verification of C sequestration. The aim of this work is to evaluate the potential advantages of using apparent electrical conductivity (EC_a)‐directed sampling to deep (0–90 cm) SOC stock assessment. We compared simple random sampling (SRS) and stratified random sampling (StSRS), with either a fixed or optimized number of samples, in fields managed under conservation agriculture and conventional tillage. The stratification in StSRS was built from EC_a maps that showed two different soil conditions—the presence or absence (high‐salinity conditions) of a strong correlation between EC_a and soil properties. Treatment and sampling design effects on SOC estimates were tested through a mixed‐model approach. Sampling efficiency was calculated by classical and bootstrap methods. Results suggested that when EC_a has a strong relationship with soil properties, StSRS was more efficient than SRS, especially when using an optimal number of samples per stratum. Stratification was based on EC_a maps of the no‐till site, which allowed a smaller minimum sample size. When stratification failed due to the effect of salinity on EC_a, StSRS efficiency was similar to SRS. These results suggest that EC_a–directed sampling, regardless of knowing the relationships between EC_a and soil properties, is a win‐win solution to advance soil characterization and SOC stock estimation in agricultural fields of the low Venetian plain. However, further research should investigate EC _a–directed sampling where strong patterns not related to SOC could lead to inappropriate stratification or suboptimal sample allocation.

中文翻译：

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土壤视在电导率定向采样设计，可提高农业领域的土壤特性

“每千分之四”的倡议要求采取土地管理措施，以增加土壤有机碳（SOC）。尽管必须进行准确的SOC测量，但是一些方法学问题可能会使C螯合的验证复杂化。这项工作的目的是评估使用表观电导率（EC _a）定向采样进行深（0-90 cm）SOC储量评估的潜在优势。我们在保护性农业和常规耕作管理的田地中比较了简单的随机抽样（SRS）和分层的随机抽样（StSRS），无论抽样数量固定还是优化。StSRS中的分层是根据EC建立的，_该图显示了两种不同的土壤条件-EC之间存在很强相关性的存在或不存在（高盐度条件）_a和土壤性质。通过混合模型方法测试了处理和采样设计对SOC估计值的影响。采样效率通过经典方法和自举方法计算。结果表明，当EC _a与土壤特性密切相关时，StSRS比SRS更有效，尤其是在每个层使用最佳数量的样品时。分层基于EC_的免耕地点图，从而可以减小最小样本量。当盐分对EC _a的影响导致分层失败时，StSRS效率类似于SRS。这些结果表明，不管知道EC _a之间的关系，都采用EC _a定向抽样。和土壤特性，是在低威尼斯平原平原农田中推进土壤特性和SOC储量估算的双赢解决方案。但是，进一步的研究应调查EC _a定向抽样，其中与SOC不相关的强模式可能导致分层不当或样本分配不理想。