biodegradable anionic polymers are disclosed which include recurring polymeric subunits preferably made up of dicarboxylic monomers such as maleic : anhydride , itaconic anhydride or citraconic anhydride . free radical polymerization is used in the synthesis of the polymers . the polymers may be complexed with ions and / or mixed with fertilizers or seeds to yield agriculturally useful compositions . the preferred products of the invention may be applied foliarly or to the earth adjacent growing plants in order to enhance nutrient uptake by the plants .