Abstract
Aiming at the improvement of land productivity, the formation of artificial aggregation was investigated. In the present study, humic acid, gypsum or minced worm was mixed as a soil conditioner with black soil (the topsoil of volcanic ash soil containing organic matter, Andisols). The change in physical properties of the sample soil was examined, first after 2.5 months, next after 20 months (both times using the same method). Water permeability, water retention capacity and size distribution of aggregates were measured as soil physical properties. Mean Weight Diameter (MWD) was also calculated from the aggregate size distribution.
By mixing with the soil conditioners, the water permeability of each sample was improved without spoiling the water retention capacity, and was improved with time passed. Even after 20 months, the aggregate rate of each sample hardly changed. However, diameter of aggregation increased especially for the sample with minced worm. In addition to these results, the relations between MWD and water permeability, and MWD and water retention capacity were found.
