激光法与湿筛－吸管法测定土壤颗粒组成的转换及质地确定

湿筛-吸管法是测定土壤颗粒组成(PSD)的传统方法,而激光法则是新兴的土壤颗粒测定方法,为了明确二者测定数据间的转换关系,应用两种方法分别测定了中国6个主要土纲的265个土壤样品。结果表明,激光法测定的土壤黏粒含量明显地小于湿筛-吸管法测定的数据,激光法测定的土壤粉粒含量明显地大于湿筛-吸管法测定的数据,而对于土壤砂粒含量的测定结果二者互有高低。两种方法测定的黏粒、粉粒和砂粒间均分别具有很好的相关性,甚至按照美国的7级分类标准,每个粒度级别在两种方法间均具有很好的相关性。按照激光法和吸管法测定数据间的转换关系式得出了用激光法测定数据的砂土、壤土和黏土质地划分界限,从而能够应用激光法测定的数据直接进行质地划分,这对于推动激光法在土壤学中的进一步应用和推动土壤科学的发展均具有重要意义。

Relationships of soil particle size distribution between sieve-pipette and laser diffraction methods

The sieve-pipette method is a traditional technique for determination of soil particle size distribution (PSD), while the laser diffraction method is a relatively new technology. To explore conversion relationship between the PSDs determined by the two different methods, 265 soil samples from 6 soil orders of the Chinese Soil Taxonomy were determined by the two methods. Results show that the clay content using the laser diffraction method was obviously lower than that using the sieve-pipette method, while the silt content using the former was higher than that using the latter, but the sand content was sometimes higher and sometimes lower with no consistent difference. However, significant relationships were found between the clay, silt and sand contents determined by the two different methods, even for each of the seven fractions of the USDA (United States Department of Agriculture) soil texture classification criteria. Based on the equations for conversion of data between the two methods, thresholds for classifying soil texture in clay, silt and sand were worked out, using the data obtained by the laser diffraction method. The findings demonstrate that data from the laser diffraction method can be directly used to classify soil texture.