Abstract: In order to study the effect of density on micro-climate in the cotton field,temperature,air humidity,soil moisture of different canopy structure with different density (9.0×104,13.5×104,18×104,22.5×104,27.0×104 plant/ha) were assessed through field trial in Akesu region in 2008. The results showed that the height of cotton plant was between 55-75cm with the designed density,and the height,stem diameter,boll-bearing branch decreased with the rise of density. During the flowering and cotton-blowing period,the cotton canopy air temperature was higher over in the other periods(the highest was more than 31℃). The diurnal temperature increased first and reduced later. The temperature in the narrow row was higher than the wider line,and the temperature was higher in height of 40cm than in the height of 20cm in the canopy. Relative humidity was in line with the upward opening parabola model,high in the flowering stage with small change and lowest at noon,which was only 40% or so and 10% higher than in the cotton wool period. The relative humidity under middle density was steady. In terms of the soil moisture,surface evaporation was serious under small density,and the transpiration from leaf was heavy with oversized density. Therefore,with moderate density treatment,soil moisture could be maintained at a good and steady condition. The soil temperature under dense canopy treatment was higher at the depth of 15cm in the early stage and then getting low due to the shadow of leaves and rising again in the later stage. However,the difference (less than 1℃) was not obvious among these treatments.

Key words: Micro-climate, Micro-climate, Density, Relative humidity, Temperature of canopy structure, Soil moisture, Soil temperature