Nuclear magnetic resonance (NMR) relaxation time (T₂) distributions are well known to be linked to the pore size distribution and show promise as a method of estimating soil texture. As traditional laboratory methods used for soil texture estimates in soil science are generally time consuming, in this study, we explore an alternative approach based on NMR T₂ distributions to estimate the soil texture of water‐saturated soil samples collected from three field sites. Using two T₂ cut‐off times, T_2a and T_2b, the T₂ distribution of a soil was partitioned into three regions, short, intermediate and long relaxation times, each of which represents the fraction of clay, silt and sand, respectively. Two approaches for determining the cut‐off times were used: the first used T₂ cut‐off times determined from the data from all sites and the second used site‐specific T₂ cut‐off times. The NMR estimates of soil texture were compared to measurements of soil texture made using the sieve–pipette method and laser diffraction particle size analysis (LDPSA). The results show that there is no universal cut‐off time for estimating the clay, silt and sand fractions based on the NMR T₂ distributions. The accuracy of NMR measurements to estimate the soil texture depends on the magnetic susceptibility of the measured material. For soils with low magnetic susceptibility (<2 × 10⁻⁴ SI) using site‐specific cut‐off times, the NMR‐derived soil texture (root mean squared error [RMSE] = 9.43%) more closely matches the soil texture measured from the sieve–pipette method than the soil texture determined using LDPSA (RMSE = 11.88%). However, the NMR estimate of soil texture breaks down for soils with high magnetic susceptibility (>4 × 10⁻⁴ SI). These results suggest that the NMR method can provide reasonable estimates of the soil texture for soils with low magnetic susceptibility.

中文翻译：

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NMR在实验室中估算土壤质地的弛豫时间：与激光衍射法和筛移液管法的比较

众所周知，核磁共振（NMR）弛豫时间（T ₂）分布与孔径分布有关，并有望作为估计土壤质地的一种方法。由于土壤科学中用于土壤质地估算的传统实验室方法通常很耗时，因此在本研究中，我们探索一种基于NMR T ₂分布的替代方法来估算从三个现场采集的水饱和土壤样品的土壤质地。使用两个T ₂截止时间T _2a和T _{2 b}，T ₂土壤的分布分为三个区域，松弛时间短，中间和长，分别代表粘土，淤泥和沙子的比例。使用了两种确定截止时间的方法：第一种方法是使用来自所有站点的数据确定的T ₂截止时间，第二种方法是使用特定于站点的T ₂截止时间。将NMR对土壤质地的估计值与使用筛移液管法和激光衍射粒度分析（LDPSA）进行的土壤质地测量值进行了比较。结果表明，没有基于NMR T ₂估算粘土，粉砂和砂子含量的通用截止时间。分布。NMR测量估计土壤质地的准确性取决于被测材料的磁化率。对于使用特定位置截止时间的低磁化率（<2×10 ^-4 SI）的土壤，NMR衍生的土壤质地（均方根误差[RMSE] = 9.43％）与从筛移液法比使用LDPSA测定的土壤质地（RMSE = 11.88％）。但是，对于具有高磁化率（> 4×10 ^-4 SI）的土壤，NMR估算会破坏土壤质地。这些结果表明，对于低磁化率的土壤，NMR方法可以为土壤质地提供合理的估计。