Establishment and Validation of Model of Soil Particle Size Distribution of Main Soils in China by Laser Diffraction Method

【Objective】 To improve the accuracy of method measuring soil particle size distribution, the new method was studied.【Method】Twenty soil samples collected from 15 provinces were determined by Laser Diffraction Method and Pipette Method.【Result】 Results show that a significant relationship was found between the clay sand contents determined by two different methods.The clay and sand content determined by using the Laser Diffraction Method were obviously lower than that by using the Pipette Method(73.4 g·kg-1and 59.6 g·kg-1), while the silt content by using the former method was higher than that by using the latter(131.2g·kg-1). A new alternative model between the two methods was found by studying the particle size cumulative distribution. If the function fitted by particle size cumulative distribution by using Laser Method of a soil is y=1 000x/(b+x), then the function by using Pipette Method is y=1000x/(1.32b-1.01+x). 【Conclusion】 The soil texture can be judged by the value calculated based on the latter function. The findings demonstrate that data from the Laser Diffraction Method can be directly used to classify soil texture.