Abstract: Field experiments under 45% shading at different stages(early, middle 1, middle 2 and later stages) of rice growth show that regardless of different stages, shading decreased the accumulation rate of dry matter and the uptake of nutrients, but increased the nutrient content in rice plant, and affected its yield in varying degrees. Shading at early growth stage mainly decreased tiller number, effective panicle number and leaf area index, and reduced yield by 11.56%, but increased plant height. At middle 1 stage, shading showed no significant influence on rice growth, and the yield was reduced by only 5.46%. At middle 2 stage, shading mainly decreased grains per panicle and 1000 grain weight, and the yield was reduced markedly by 30.80%. At later stage, shading decreased the percentage of filled grains and 1000 grain weight, and the yield was the lowest, reduced by 55.40%. Suggestions on the way of regulating sowing and transplanting dates and making fertilization decision under low light intensity also put forward in this paper.

Key words: Shading, Growth and development, Uptake of nutrient, Yield formation, variability, sensitivity analysis, Bartels statistics, Hurst coefficient, Lancang River.