At season-frozen podzolic loamy soils of the Republic of Komi the experimental studies were carried out with a use of isotope indication (15N) method. The results of the studies revealed, that soil freezing promotes nitrogen transfer with up going water flow to the freezing point and its accumulation in the frozen layer zone. The above process is connected with a convective water transfer, which is caused by the temperature gradients (thermocapillary transfer). Stabilization of the freezing zone in February-March reduced nitrogen transfer in soil profile. Soil melting (April-May) lead to insignificant nitrogen loss by leaching out. Freezing layer, remained during the spring period at 21 (24) - 31 (34) cm deep, reduced water exchange between upper and lower layers, which reduced the intensity of the vertical nitrogen migration and increased the lateral outlet. The results of the experiment are also confirmed by the all-the-year-round lysimetric water control. Vertical water filtration over 0-50 cm of soil layer, during five years on average, was not significant, including: March-April - 2.5%, May-June - 2.2%, August-November - 8.5%, December-February - 1.7%.
Low (weak) descending nitrogen migration on profile is connected with genetic peculiarities of podzolic soils: formation of freezing hydrological bi-component (water supporting layer), presence of texture-differentiated, low permeable to water horizon, which contains maximum of silt and one and a half oxides, low crack formation, high sorption capability to nitrates. The illuvial horizon is a nitrogen accumulator, which prevents descending migration and its unproductive losses. The cryogenic de-watering and soil melting lead to the destruction of the organic nitrogen containing substances and to the accumulation of mineral nitrogen forms in soils. The above process has both biotic and abiotic character.
Dr. Vasily A. Beznosikov Head of the Soil Science Department Institute of Biology Komi Scientific Center Ural Division of the Russian Academy of Sciences St. Kommunisticheskaya 24, Syktyvkar, 167610 Russia Phone: (8212) 42-15-51 Fax: (8212) 42-01-63