Nitrogen fertilizer compositions based on polyphosphate caged structure

A urea-polyphosphate composition comprising urea, a polyphosphate, inorganic cations, and a water-insoluble fraction having (a) a nitrogen content in the range of 5 wt % to 40 wt %, (b) a phosphorus content in the range of 1 wt % to 20 wt. %, (c) primary inorganic cations in the range of 1 wt % to 20 wt % wherein the primary inorganic cations are selected from the group consisting of ammonium, calcium, iron, magnesium, and potassium cations and combinations thereof, (d) a molar ratio of nitrogen to the combined total of the primary inorganic cations in the range of 2:1 to 40:1, (e) a number average chain length of polyphosphate groups of 1.1 to 20 when orthophosphates are included in the number average chain length calculation, (f) a molar ratio of nitrogen to phosphorous in the range of 3:1 to 60:1, and (g) a solubility in citric acid such that (i) at least 70 wt. % of each of the total nitrogen and total phosphorous in the water-insoluble fraction is soluble in 2 wt. % citric acid, and (ii) at least 50 wt. % of each of the total nitrogen and the total phosphorous in the water-insoluble fraction is soluble in 0.2 wt. % citric acid, wherein the water-insoluble fraction is obtained by placing 2 g of the urea-polyphosphate composition on a filter paper in a funnel over a Whatman 1 filter paper, leaching with 10 mL deionized water added dropwise from a burette for 8 minutes at 25° C. and collecting the solid residue.