Yearly Changes of Water Retentivity and Other Relevant Physical Properties of the Rotational Farm Soils

Abstract

Water retentivity and other relevant physical properties of the rotational farm soils were investigated for three years. The yearly changes of those are discussed in this paper. Results obtained are as follows ; 1. The air ratios at pF 1.6 of the upper soil layer (0-15 cm in depth) increase yearly and exceed the aimed value for dry fields after three years. 2. The values of apparent specific gravity of the upper soil layer decrease yearly. 3. The readily available moisture content (pF 1.8-3.0) of the upper soil layer increases yearly. But even after three years, that still does not reach the aimed value for dry fields. 4. In the lower soil layer (15-30 cm in depth), the yearly changes of the air ratios at pF 1.6, apparent specific gravity and the readily available moisture content are not remarkable. 5. The volumetric water content at the same value of pF decreases yearly in the upper and lower soil layers. 6. The rates of change of the volumetric water content increase around pF 2.2 in the upper soil layer yearly.