The goal of the present work is to investigate general regularities of same physical processes forming hydrothermal regime of soil covered by straw mulch during could season and to generalize of results in the form of mathematical models.

The following questions were considered. Impact of the mulch composed by organic remains on soil temperature profile and soil freezing during winter. Thawing and heating soil covered by straw mulch following snowmelt. Decreasing of unproductive evaporation of water from soil covered by mulch. The determination of the heat conductivity and vapor diffusivity of straw mulch. Mathematical models describing dynamics of soil temperature in winter and spring and evaporation of soil water for soil covered by mulch layer.

Field experimental investigations have been carried out in the area of the Kursk Biosphere Station (forest-steppe zone). A method has been devised for determining the effective thermal conductivity of the mulch by measuring the depression in the soil-water evaporation. Determination have been made on the effective thermal conductivity for straw mulch and for the vapor diffusion in it.

The theoretical part of work is based on mathematical modeling of heat and vapor transport in the system consisting of snow cover, frozen soil, thawed soil and mulch layer. A models of the dynamics of freezing, thawing and evolution of the temperature profile of soil are developed. Model calculations and measurements are compared on the dynamics of the boundaries of the frozen zone and the temperature for the fallow soil, soil covered with straw mulch and soil with dead natural vegetative cover. The measurements and calculations indicate satisfactory agreement.

Institute of Water Problems
Russian Academy of Sciences
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E-mail: gusev@iwapr.msk.su