The invention relates to a preparation method of a
water retention type
fertilizer. The preparation method comprises the following steps that: 50 to 80 weight parts of crylic acid is placed in a container, 350 weight parts of de-ionized water is added to be stirred uniformly, and
potassium hydroxide is used for regulating the PH value so that the PH value of the
system is about 7.0; 30 to 50 weight parts of dry natural sheep
manure is weighed and is crushed into
powder of 100 meshes; the prepared sheep
manure powder is added into the solution, next, 60 to 90 weight parts of carbamide and 10 to 15 weight parts of
diammonium phosphate are added to be stirred and dissolved, then,
nitrogen gas is introduced for stirring for 30 minutes at a high speed; mixture is heated to 65 DEG C at the pressure being 0.03 to 0.05 Mpa, and the pasting is carried out for 20 minutes; and 1.0 weight part of
potassium persulfate salt and 1.0 weight part of
sodium sulfite are added to be stirred uniformly, 0.5 weight part of N,N'-
methylene bisacrylamide is added, the
polymerization is carried out when the temperature is 50 to 60 DEG C, the
polymerization time is one hour, crosslinked polymeric products are obtained, and the final product is obtained after nutritional ingredients are supplemented. The preparation method has the beneficial effects that the
water retention type
fertilizer obtained through the method provided by the invention has good
water retention performance and good biologic and
chemical stability, meanwhile, the natural sheep
manure is used as a base material, the effective nutritional ingredients of the sheep manure are reserved, the effective utilization of resources is widened, and the cost can be greatly reduced.