Water Retention Capacity of Soils in the Altai Region

Water retention curves (WRC) and some physical and chemical properties (particle-size composition, soil density, organic matter content, etc.) were determined for the major soil types of the Altai Region: southern chernozems of moderately dry steppe (Calcic Chernozems) and ordinary chernozems (Haplic Chernozems) of steppe with forest groves in local depressions, leached chernozems of the Altai foothills (Luvic Chernozems (Pachic)), and chestnut soils (Kastanozems) of dry steppe. These soils differ by texture. Overall, 420 soil samples were examined. The water retention curve was experimentally determined by centrifugation and capillarimetry, and approximated on the basis of the van Genuchten equation. The parameters of approximation were used for hydrological grouping of the soils by texture, which becomes heavier from the loamy sandy soils of dry steppe towards heavy loamy soils of the Altai foothills. The hydrophysical parameters are not differentiated along the soil profile and generally are in agreement with the humus accumulation process and the natural or anthropogenic soil compaction. An increase in parameter α reciprocal to the bubbling pressure is observed upon the transition from steppe Chernozems towards Kastanozems of dry steppe. The determination of this parameter is particularly important for modeling water and aeration conditions of irrigated soils and potential waterlogging. Quantitative descriptions of water retention curves with the use of approximation parameters made it possible to develop physically substantiated models for soil reclamation purposes.