Abstract: It is in the booting stage that the soil water influences seed setting of foxtail millet (Setaria itulica Bcauv.). When soil water is too much or too little, the seed setting rate, seed number per spike and yield ail decline obviously. The best condition for grain development is to keep soil moisture at 70% of capillary water. Insufficient of soil water affects the root system activity and water status inside of plants first, therefore, influences the air exchange between inside and outside of plants, reduces the rate of photosynthesis and respiration of the leaf, lowers the permeability of cell membrane, causes changes of substances metabolicem process, and decrease of the accumulation of organic matters, and results in nutritional inadequancy of the spike and in formation of abortive grain.When soil water is excessive, the aeration is poor, the activity of root system is affected, the bleeding decreases, metabolic process and substances tranport in plant are controlled. So the nutrition in spike is poor and the abortive grain is formed.

Key words: Foxtail millet, Soil water, Seed setting rate, Abortive grain rate