Seasonally frozen meadow-boggy soils are widely spread on the territory of Russia and actively involved in agricultural rotation. A great influence on formation of these soils shows hillocky relief, often thermokarst origin, causing irregularity of water distribution in soil, enterning and discharge of heat, freezing and thawing. To involve such soils in agricultural rotation it is necessary to conduct a number of field management actions, first of all - field leveling, cutting off hillocks, ecuiplaining of surface.

Under the following polishing vegetation is covered of frost mouds are destroyed that results in distributing of initial hygrothermal and thermophysical regimes, redistribution of solid and liquid precipitations. Turn-under of hillocks and vegetations, smoothing over of mouds promotes the more even distribution of snow during wind transfer, although its power decreases in 1.5-2 times in comparison with virgin soil where it reaches 50-60 cm. Small snow cover on tillage decreases its heat defence effect, and soil freezing becomes in 2-3 ten-day periods of October, on virgin soils on 2-3 days later.

The most low temperatures of arable soils -25...-30 oC was noted in second decade of February. Temperature of virgin soils at the time was on 3-5 oC higher. Freezing becomes before forming of stabile snow cover and goes more intensive on arable soils - 2.8 cm/day, on virgin soil - 2.2 cm/day. Although arable soil accumulates more cold thawing of it in spring goes more intensive - 20 cm by 5-th of may, and on virgin soil - 10 cm by third decade of may. Seasonally thawed layer on arable soil reaches 180 cm by the third decade of July, on virgin - by second decade of august.

Aleksandr N. Butsenko, Institute of Soil Science and Photosynthesis, R.A.N.
142292 Pushchino. Moscow Region, RUSSIA
Telephone (095) 923-35-58