INFLUENCE OF MOISTURE PRESSURE, SPECIFIC SURFACE, AND PORE-SPACE STRUCTURE OF SOILS ON MOISTURE AVAILABILITY TO PLANTS

Vegetation experiments with barley seedlings on different fractions of quartz, loamy parent rocks, sand, Serozem (Gray Earth), and Chernozem have established the high correlation between relative guttation and relative growth. In terms of guttation intensity and growth rate of pl ants, substrate moisture ranges can be identified which correspond to different degrees of moisture availability to plants. The sharp decrea se (by half) in guttation and growth in conjunction with excess moiste ning coincides with the capillary pressure of soil moisture, which cor responds to bubbling (sharp increase in air-permeability of soils). A linear dependence exists between the logarithm of the modulus of press ure of bubbling and the logarithm of the diameter of the predominant e lementary soil-particle fraction. Upon a decrease in soil moisture, th e critical capillary-sorption pressure of soil moisture at which gutta tion ceases is linked by a linear function to the specific surface of the soil's solid phase.