Soil water content (θ) influences physical, chemical, and biological processes in the soil. Near‐surface θ (<1‐cm depth) is particularly important for surface energy partitioning, but few techniques are available for near‐surface in situ θ measurements. Heat‐pulse sensors can be used to determine the soil volumetric heat capacity, which is linearly related to θ. Here we describe the principles and procedures of determining near‐surface in situ θ with a heat pulse sensor. The main limitations and potential errors associated with the method are also presented. When ambient soil temperature drift and the soil–air interface effects are addressed, the error in the heat‐pulse‐determined θ is greatly reduced. For an example, data series with θ data determined by gravimetric initial θ and heat‐pulse‐based change in θ (Δθ), results agree well with gravimetric θ values, yielding a coefficient of determination of 0.95. We conclude that heat‐pulse sensors are useful tools for continuously and nondestructively determining near‐surface θ of non‐shrink–swell soils.

中文翻译：

---

热脉冲方法的进展：测量近地表土壤含水量

土壤含水量（θ）影响土壤中的物理，化学和生物过程。近表面θ（深度小于1 cm）对于表面能分配特别重要，但是很少有技术可用于近地表原位θ测量。热脉冲传感器可用于确定土壤体积热容，它与θ线性相关。在这里，我们描述了使用热脉冲传感器确定近地表原位θ的原理和程序。还介绍了与该方法相关的主要局限性和潜在错误。解决了周围土壤温度的漂移和土壤-空气界面的影响后，由热脉冲确定的θ误差将大大降低。例如，具有由重力初始θ和基于热脉冲的θ变化（Δθ）确定的θ数据的数据序列，结果与重量θ值非常吻合，确定系数为0.95。我们得出的结论是，热脉冲传感器是连续无损确定非收缩膨胀土壤近表面θ的有用工具。