Recent studies have shown that soil particle size analyses using laser diffraction method (LDM) can give compatible results compared with traditional sedimentation based methods, if the clay-silt particle size cutoff is transformed. Additionally, procedures including separation of the sand fraction by wet sieving and running a well dispersed sample of only fractions smaller than sand during laser diffraction measurement, have given promising results. The main purpose of the present study was to test a combination of these approaches for determining cutoff transformed LDM values on 44 soil samples from agricultural sites spread over Sweden, including its compatibility with the sieve and pipette method (SPM). Furthermore, these results were compared with results of transformed LDM values based on pedotransfer functions between measured LDM and SPM. Also LDM related aspects concerning scattering parameters, repeatability and organic matter calculations were studied. To find the optimum clay-silt cutoff, Lin’s concordance correlation coefficient (Lin’s CCC) was calculated. The highest value (0.977) was found with the 3.409–3.905 µm bin (a refractive index of 1.52 and an absorption coefficient of 0.1 was used). The pedotransfer-transformed LDM approach showed equally high Lin´s CCC as the cutoff-transformed approach for the different soil particle fraction size classes. With the cutoff-transformed LDM approach, 36 out of 44 samples were assigned to the same texture class as SPM, and with the pedotransfer-transformed LDM, the corresponding number was similar (34 out of 44 samples). The results here are promising for application in routine soil analyses, but more specific transformed clay-silt cutoffs and pedotransfer functions for LDM versus SPM should ideally be established for different types of soils. For this, microscopy and image analysis methods to help understand and quantify the influence of particle shapes on obtained particle size distributions are useful.

中文翻译：

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激光衍射土壤粒度分布分析的研究，以获得与筛子法和移液管法兼容的结果


最近的研究表明，如果改变粘土-粉砂粒径截止值，则使用激光衍射法 (LDM) 进行土壤粒径分析，与传统的基于沉降的方法相比，可以给出兼容的结果。此外，包括通过湿筛分离沙子部分以及在激光衍射测量过程中运行仅比沙子小的部分分散良好的样品在内的程序已经给出了有希望的结果。本研究的主要目的是测试这些方法的组合，以确定来自瑞典各地农业场所的 44 个土壤样本的截止转化 LDM 值，包括其与筛子和移液器方法 (SPM) 的兼容性。此外，将这些结果与基于测量的 LDM 和 SPM 之间的pedotransfer 函数转换的 LDM 值的结果进行比较。还研究了涉及散射参数、重复性和有机物计算的 LDM 相关方面。为了找到最佳的粘土-粉砂截断值，计算了 Lin 的一致性相关系数 (Lin's CCC)。最高值 (0.977) 出现在 3.409–3.905 µm 区间（使用的折射率为 1.52，吸收系数为 0.1）。对于不同的土壤颗粒粒径类别，pedotransfer 转换的 LDM 方法显示出与截断转换方法同样高的 Lin 的 CCC。使用截止变换的LDM方法，44个样本中的36个被分配到与SPM相同的纹理类别，并且使用pedotransfer变换的LDM，相应的数量相似（44个样本中的34个）。 这里的结果有望应用于常规土壤分析，但理想情况下应该针对不同类型的土壤建立 LDM 与 SPM 的更具体的转化粘土-粉土截断值和土壤转移函数。为此，显微镜和图像分析方法有助于理解和量化颗粒形状对获得的颗粒尺寸分布的影响。