A multiple-component fertilizer material adapted for fertilizing a crop and comprising a first fertilizer product component and a second fertilizer product component for application onto soil in which said crop will grow: the first fertilizer product component including an ammoniacal fertilizer selected from the group consisting of ammoniacal nitrogen-containing fertilizer, and a partial calcium salt of a first copolymer comprising maleic and itaconic moieties, said partial calcium salt of said first copolymer applied to or mixed with said ammoniacal fertilizer as an aqueous liquid product and having a pH of from 1 to 3.5, said partial calcium salt of said first copolymer being mixed with said ammoniacal fertilizer product at a level of from 0.01-2% by volume, based upon the total volume of the first fertilizer product component taken as 100% by volume; and the second fertilizer product component including a phosphorous fertilizer and a partial sodium salt of a second copolymer comprising maleic and itaconic moieties, said partial sodium salt of said second copolymer applied to or mixed with said phosphorous fertilizer as an aqueous liquid product and having a pH of from 5 to 10, said partial sodium salt of said second copolymer being mixed with said phosphorous fertilizer product at a level of from 0.01-2% by volume, based upon the total volume of the second fertilizer product component taken as 100% by volume; said first and second fertilizer product components being present in synergistically effective amounts, such that the coordinated amounts of said first and second fertilizer product components give crop yields greater than a mere additive effect obtainable through the use of the respective said first and second fertilizer product components alone in the same amounts, wherein said first and second fertilizer product components in case of being liquid are kept separate for separate substantially simultaneous or in serial order application thereof. the first fertilizer product component including an ammoniacal fertilizer selected from the group consisting of ammoniacal nitrogen-containing fertilizer, and a partial calcium salt of a first copolymer comprising maleic and itaconic moieties, said partial calcium salt of said first copolymer applied to or mixed with said ammoniacal fertilizer as an aqueous liquid product and having a pH of from 1 to 3.5, said partial calcium salt of said first copolymer being mixed with said ammoniacal fertilizer product at a level of from 0.01-2% by volume, based upon the total volume of the first fertilizer product component taken as 100% by volume; and the second fertilizer product component including a phosphorous fertilizer and a partial sodium salt of a second copolymer comprising maleic and itaconic moieties, said partial sodium salt of said second copolymer applied to or mixed with said phosphorous fertilizer as an aqueous liquid product and having a pH of from 5 to 10, said partial sodium salt of said second copolymer being mixed with said phosphorous fertilizer product at a level of from 0.01-2% by volume, based upon the total volume of the second fertilizer product component taken as 100% by volume; said first and second fertilizer product components being present in synergistically effective amounts, such that the coordinated amounts of said first and second fertilizer product components give crop yields greater than a mere additive effect obtainable through the use of the respective said first and second fertilizer product components alone in the same amounts, wherein said first and second fertilizer product components in case of being liquid are kept separate for separate substantially simultaneous or in serial order application thereof.