The invention is directed to a crumbly, water-absorbing, soil-like hydrogel. The hydrogel comprises finely comminuted mineral substances, such as igneous rock; water-soluble alkali-silicate; solid and liquid nutrient additives; and ballast, bound in a cross-linked polymer. The hydrogel is structured like a sponge and absorbs water and liquids when in contact with water or aqueous liquids. The mineral substances present in the hydrogel may be present in an amount of at least 30% by weight of the dried hydrogel. Also, the invention encompasses methods of producing acidic and neutral to weakly alkaline hydrogels.