Abstract: Hexi region in Gansu Province is an irrigation agriculture area in China.Insufficient water resources is the major limiting factor for the agriculture production.The conventional water-storing irrigation,with high quantity and large scale,occurs in the end of the autumn or in the beginning of the winter(from mid-October to mid-November).The irrigation water derives from melted ice and snow in the Qilian mountain,and the river runoff decreases in the winter.Limited water-storing irrigation leads to contraction between water demand and supply,and excess irrigation often easily results in soil salinization.A field experiment was conducted during the period 1994-1996 in Hexi region to study the effect of the time and amount of irrigation,and surface mulching on the water storage.The results showed that the amount of irrigation,no less than 120 mm in mid-October and 90 mm in November,could ensure the seedling emergence of the spring wheat.The water-storing irrigation saved 50~80 mm,and there is a great potential to develop.The amount of water consumption is relative small during the mid-September to mid-October,it is very beneficial for water-saving irrigation to advance the irrigation time to the mid-September.Also,the results suggested that the last irrigation of autumn crops could be combined with storing irrigation as a one.The amount of irrigation increased up to 150 mm,and the timely cultivation,and harrowing could ensure high percentage of seedling emergence after irrigation.Surface straw and film mulch can effectively conserved moisture after water-storing irrigation.The mulching can reduce the amount of irrigation and advance irrigation time.The amount of irrigation can be dropped to 60 mm,and the time can be advanced to mid-September.The straw cover can not be applied when the high quantity of water is irrigated,which can lead to seed decomposed due to low soil temperature and high moisture.

Key words: the time for water-storing irrigation, the amount of water-storing irrigation, water-saving, technique, Hexi oases