Abstract: A method for enhancing the water retention capacity of soils and providing plant nutrients thereto over an extended period of time uses chryso-zeolites type A and/or X admixed with a soil at 2 to 30% by weight of the soil. The chryso-zeolites comprise a magnesium-leached asbestos matrix with a zeolite crystalline structure thereon. The composition of the chryso-zeolites includes silica--35 to 60% by weight, MgO--0.1 to 10% by weight, Al.sub.2 O.sub.3 --10 to 45% by weight and from 10 to 25% by weight of CaO, the CaO being optionally substituted by one or more of plant nutrient components such as potassium or ammonium. The content of sodium oxide is reduced to less that 3% by weight. The chryso-zeolites of the invention exhibit a very low phytotoxicity, good water retention and easy substitution of calcium by other nutritive components.