NSP is an excellent P source for plants and has the added advantage of containing about 12 percent sulfur as calcium sulfate. NSP is used as a direct-application material and as an ingredient in some mixed fertilizers. The resulting product is mainly MCP, with very little sulfur present since sulfuric acid is not directly used in the production process. Because of its higher analysis, which results in reduced shipping and handling costs, TSP is favored over NSP when sulfur is not needed. Ammonium Phosphates Ammonium phosphates constitute a large class of P fertilizers produced from phosphoric acid and anhydrous ammonia.
Some ammonium phosphates contain additional materials, such as sulfuric acid and urea.
Three of the common ammonium phosphates are monoammonium phosphate, diammonium phosphate, and ammonium polyphosphate. Although an excellent, high-analysis source of P with superior handling characteristics, DAP can cause germination damage if high rates are placed in direct contact with the seed. Such damage results from the formation of free ammonia, especially on high-pH soils. For applications other than direct seed contact, however, DAP, MAP, and APS are comparable and excellent P fertilizers. These materials have been developed during the last 20 years Polyphosphates are formed when two or more phosphoric acid molecules are chemically combined by removing water.