Multiple-component fertilizer materials and methods of use are provided, wherein the fertilizer materials include first and second fertilizer products respectively including an ammoniacal fertilizer (e.g., urea) in combination with a partial calcium salt of a selected copolymer, and a phosphorous fertilizer (e.g., DAP) in combination with a partial sodium salt of a selected copolymer. The copolymer fractions of the first and second fertilizer products are most preferably copolymers of itaconic acid and maleic anhydride. The fertilizer materials give synergistically enhanced crop yields when applied to soil or growing plants.