STUDY ON SOYBEAN GROWTH AT DIFFERENT WITH VARIED ELEVATIONS ECOLOGICAL CIRCUMSTANCES IN SICHUAN

The ecological circumstances of soybean fields are greatly varied at different altitudes. The microclimate for soybean fields between 400～1 400 m above sea level was observed as follows in φ (N)32°14′～32°56′, λ (E)104°36′～104°51′: As altitude rises per 100 m,mean air femperature decreases by 0.72 ℃,relative humidity increases progressively by 1%,and annual precipitation increases by 63.0 mm (between 400～600 m) and 106.8 mm (800～1400 m), respectively. Sunny hours tend to be changed in parabola. The middle March is the initial period in which daily mean air temperature rises steadly over 12 ℃ at 400 m and the period is delayed for about 5～10 d as the altitude rises per 100 m. Effective accumulated temperature in the fields above 12 ℃ at different altitudes was 3 621.2 ℃(400 m),3 245.0 ℃(600 m),3 149.9 ℃(800 m), 2 804.8 ℃(1 000 m),2 082.1 ℃(1 200 m) and 1 950.1℃(1 400 m),respectively. Owing to the apparent effects of inversion and south north facing slopes,soybean fields with high yield are found in some regions. This study provides the scientific basis for the layout and cultivation of soybean in various regions at different altitudes in Sichuan.