It is proved that a promising display of transition from traditional to soil protective and minimal cultivation technologies  trend in agriculture is the zero tillage technology in which it is subjected to mechanical stress only in the area of the drills opener that makes a crack at sowing soil layer and places her seed there. The rest of the factors that may influence soils physical parameters are present in this technology, as well as in others.

Among the most important agrophysical parameters is soil density which can be regarded as an integral factor of its agrophysical condition. For the majority of crops on medium and heavy alumina soils optimal conditions for growth and development of crops consist in soil density ranged from 1 g/cm³ to 1.03 g/cm³, on sandy and semisandy - 1,20-1,50 g/cm³.

The optimal density depends on soil type, grain size and biological characteristics of crops.

The 3-year research data on the influence of No–till cultivation technology for soybeans on its density and moisture reserves in soya-corn  crop rotation are presented in the paper.

The obtained experimental results show that the density of the soil depends significantly on the methods of its cultivation, which is most notable in the complete germination of soya. In the mass germination the density of the soil under soybeans in 0-20 cm layer under traditional cultivation (plowing) made in 1.15 g/cm³ in 2011, and 1.26 g/cm³ in 2013, while in variant with using No-till cultivation technology  the density increased, by 8.7 and 6.3 % respectively. A slight increase in the soil density was observed in these variants in soybean seed filling phase as well. Soil structure density increase in  0-20 sm layer was a result of  3 years (2011-2013) No-till technology which made 6.7% of the full germination period, and 3.1% in the phase of seed filling.

The average equilibrium bulk density is 1,1-1,25 g/cm³ for typical chernozem, 1,35-1,4 g/cm³ for loam and sod-podzol soils, 1.5-1.6 g/cm3 for sandy loam and sandy soils.

It has been experimentally proved that the density of the soil is much more influenced by mechanic cultivation than by natural processes. The density fluctuations range, influenced by changes in humidity and temperature, fluctuates in the range of 0.05 g/cm³ in the natural conditions. Depending on the type of plant roots this range is somewhat wider ±0,20-0,30 g/cm³. Under mechanical cultivation of medium or heavy loam chernozem it can reach 0.40 g/cm³.

Most of soil cultivation processing methods aim at bringing the soil density to its optimum value - within 1,12-1,27 g/cm³. The value of this index influences almost all water and physical soil properties: porosity, permeability, moisture, water supplies, soil resistance to erosion. Recompressing of soil from 1.30 to 1,45-1,55 g/cm³ takes place due to the excessive use of the technology in the growing of field crops, lack of tillage minimization, which causes a dramatic reduce in crop yields and production costs increase.

It is proved that under No-till cultivation technology in soya fields in the 2 part soya-corn rotation the density in the plow layer (3.1 and 6.7 % on the average for 3 years) increases slightly. Thus soil productive moisture stocks in this and deeper (20-40 cm)  layer remain traditional.

Key words: zero-tillage, soil density, moisture stock, soya.