Moisture content and thermal properties of gray forest sandy loam soil in iris agrocenosis

Abstract

The research goal was to study the relationship of the thermophysical properties and moisture content of gray forest sandy loam agricultural soil transformed by long-term use associated with irrigation under bearded iris planting. In 2023, the soil emerged from winter with low moisture content. Only 13.8 mm was accumulated in the arable horizon which corresponded to “satisfactory” level (according to the A.F. Vadyunina scale) of available moisture storage. At the same time, in the podzolized horizon, the available moisture storage was zero. By the end of June, the amount of available moisture storage in the 65 cm layer increased by 5 mm only, and in August it fell again to 11.7 mm, i.e. to the state of “bad” even for sandy loam soil. Only by the beginning of October everything returned to the original moisture content. In accordance with moisture, the thermal physical coefficients also changed dynamically during the growing season. The thermal diffusivity of the gray forest soil remained constant and equal to 0.64 × 10^-6 m² s. The thermal conductivity coefficient was also subject to slight fluctuations. The summer of 2024 was hot only in July, and in the second half of August and throughout September there was intense precipitation which caused increased moisture content in the soil profile. Thus, the available moisture storage in the arable layer in May was 34.1 mm, and in September even 58.0 mm. As a result, the heat accumulation and heat transfer coefficients increased sharply which in the arable layer were equal to 3.21 × 106 J (m³ K) and 1.85 W (m K), respectively. At the same time, in the underlying horizons, both moisture content and thermal physical indices remained low. However, available moisture storage in the root zone (0-65 cm) corresponded to the “good” level.