Soil Laboratory - Particle Size Analysis

In this laboratory, the soil samples are pre-spread, weighed and their grain size determined. The particle size composition can be determined by sieving. For this purpose, sieves with increasing mesh sizes are placed one above the other on a vibrating screening machine, starting with the lower collecting plate for the finest particles. The sieves are set in vertical oscillation by an electromagnetic drive. This results in an even distribution of the sieved material over the meshes. Mass fractions of grain fractions with a diameter > 0.063 mm are determined by dry sieving. If particles ≤ 0.063 mm are also contained, they are separated by wet sieving. The grain size composition of the clay and silt fraction (< 0.063 mm) can now be determined by sedimentation in a Köhn apparatus, for example. The physical background is the fact that the sedimentation velocity in a liquid is determined by the size of the individual grains. Additionally, the humus content can be also determined in this lab.