OPTIMUM REGULATIONS OF ECOLOGICAL SYSTEM OF PADDY FIELD
稻田生态系统的优化调节

In order to clarify the characteristics of ecological system of paddy field, to optimize functions of the system and to increase grain yield of the plants, experiments, employing Liaojing No 5 or Shennong No.91 as sample, have been conducted since 1985. In the experiments, effects of seeding rate, planting density, and amount of nitrogenous, phosphoric and potassium fertilizer on yield of paddy field have been investigated. The experimental results indicated that the characteristics and functions of the plant canopy structures varied with treatment factors. The relationship between grain yield and treatment factors fitted multiple quadratic function; and the relationship between number of panicles per unit area, or leaf area index, and grain yield fitted in second order model. There were appropriate values for the number of individual in colony and for leaf area index of the plant. There was a significant negative correlation between leaf area index of the plants and light intensity, or air temperature, in the canopy, while the correlation between the leaf area index and relative humidity in the canopy was significant positive. Accordingly, light intensity, relative humidity and air temperature in the canopy were controlled and regulated by leaf area index of the plant. The experiment also indicated that the plants with ideal canopy structure and high growth rate in the late growth period tend to become high yielding ones. To establish and regulate the ecological system of paddy field, a series of measures, which composed of choosing varieties with erect panicles, thin sowing to rear healthy seedlings, sparse transplanting, proper fertilizing, effective irrigating, weeding with herbicides, preventing plant diseases, eliminating pests, and regulating the growth and development of the plants, should be putted into practice.