On the bases of observation data from various sources of the influences of seeding density on the microdimate in analyses the crop have cover been The made main results are as follows: 1. Within the crop cover the decrease i}; radiation and temperature in the vege- tative period is proportional to the logarithm of seeding density. 2. The soil moisture and the relative humidity of the air in the crop cover decrease (the former) or increase (the later) lineally with the increase of density of seeding. 3. The variation of wind velocity with density of seeding can be expressed approxi-mutely by this equation: u=u₀e^-fN, where U signfies the wind velocity within the crop cover; U₀ the velocity above the crop surface; N the density of seeding and f a parameter. 4. For each crop there is an optimum seeding density- that would lead to maximum yield.