Simplified method for soil particle-size determination to accompany soil-quality analyses

Soil textural analysis is a key component of any minimum data set used for assessing soil quality and sustainability of agricultural-management practices, However, conventional methods of soil textural analysis can be costly and time-consuming. The objective of this study was to develop a rapid and simple method for evaluating soil particle-size distribution, which could be employed as a tool For initial soil-quality assessment. The method uses a combination of sieving and sedimentation steps and is designed to be used in conjunction with analysis of particulate organic matter (POM), or as a stand-alone textural analysis. Soils of varied texture and organic-matter content were collected from six sites in the Great Plains, Their sand, silt, and clay contents were determined using the proposed methods and standard hydrometer and pipette techniques. Averaged across all soils, absolute differences between the proposed and standard pipette analyses were <2% for sand, silt, and clay. Relative differences were 6, -1, and -4% for sand, silt, and clay, respectively. Coefficients of variation within soil samples averaged <5% for sand, silt, and clay fractions. Regression analysis between proposed and standard pipette methods produced coefficient of determination (r(2)) values of 0.99, 0.98, and 0.93 for sand, silt, and clay, respectively, and 0.98 across all particle-size ranges, The method provides an inexpensive and reliable estimate of soil texture, useful in soil-quality assessment.