Improved, low-pH aqueous polymer mixtures are provided which can be applied directly to soils or incorporated within ammoniacal nitrogen-containing fertilizers to inhibit nitrification in soils, thus enhancing plant uptake of ammonium and yields. The polymers are advantageously used as metal (e.g., Ca) salts or complexes at pH levels of up to about 2. The polymers have anionic functional groups and are highly water dispersible.