A composite particle and a population of particles comprising a water-insoluble polyphosphate composition, methods of producing, and methods of using the same are provided. The polyphosphate composition may comprise at least one alkaline earth metal selected from calcium and magnesium and optionally at least one nutrient ion selected from the group consisting of potassium, ammonium, zinc, iron, manganese, copper, boron, chlorine, iodine, molybdenum, selenium or sulfur.