Estimation of water holding capacity of soils using data from different types of particle size analyses

Determining the particle size distribution of soils helps to monitor the hydrophysical properties of the soil (e.g. water conductivity or water holding capacity). Climate change increases the importance of water retention and permeability, as extreme weather events can severely impair the water supply of drought-prone plant stocks. The amount of water is expected to decrease. At the beginning of the research, we have developed a measurement method to replace the classical “pipette” sedimentation method with the laser diffraction method. The theoretical background of laser diffraction measurements is already known, but its practical application for estimating soil’s water holding capacity is uncommon in detail. The developed, modified Thornthwaite model considers soil properties (e.g. root depth, topsoil layer thickness) and size distribution (silt and clay fraction) of soil particles combined with the most significant soil properties. The pre-sieving of soil aggregates, the pre-treatment (disaggregation and dispersion) of the samples greatly influence the obtained results. In addition to the sedimentation method, instrumental measurements (Mastersizer 3000) were applied with three variants of pre-treatment. For comparison, the results of a Leptosol, a Cambisol, and a Luvisol were prepared for the first modified Thornthwaite water balance model. Significant differences appeared especially during drought periods that could be a basis for studying the drought sensitivity of soils. By the development of our method, the water holding capacity of soil can be estimated; therefore, adapting forest management could be planned against climatic and pedological transformations.