Super absorbent polymer(SAP)is not only widely used in sanitary materials, industrial dewatering materials, sludge solidifying materials, anti-condensation materials, etc., but also has begun to be used in the agricultural field, and achieved obvious effect. Of course, water retention agent is not omnipotent, can not think that the use of water retention agent does not need to irrigate, or increase the amount of water retention agent can save a lot of water.