Abstract: A method of improving water retention characteristics of soil by using water absorption polymer, including the steps of forming a water impermeable layer in a subsurface layer of the ground, and providing a water absorption polymer layer in an upper region of the water impermeable layer. The method is executed by an apparatus for forming a water impermeable layer in a subsurface layer of the ground, the apparatus also being used to mix water absorption polymer in the soil in an upper region of the water impermeable layer, by an injecting apparatus having a drilling function.

Abstract: A process for producing an inorganic compound-containing urea resin, which comprises adding an acidic gelling agent to an aqueous urea-formaldehyde precondensate solution to prepare a urea resin-containing product, and either(1) mixing the product with a reactant which reacts with the gelling agent to form inorganic particles substantially insoluble in water, or(2) separating the urea resin from the product, mixing the resin-freed mother liquor with such a reactant as stated above, and mixing the resulting inorganic particles with the separated urea resin.

Abstract: A slow release nitrogen fertilizer comprising a hydrous cured product of urea-formaldehyde condensate in which the total methylol content is 0.1 to 1.0% by weight (based on the weight of hydrous product) and the hot water-dissolution percentage [percentage of the cured product dissolved in hot water at 80.degree. C. when the product has been immersed therein for 30 minutes (based on the weight of anhydrous product)] is 10% by weight or less.