Triple superphosphate (TSP) was one of the first high-analysis phosphorus (P) fertilizers that became widely used in the 20th century. Technically, it is known as calcium dihydrogen phosphate and as monocalcium phosphate, [Ca(H₂PO₄)₂ .H₂O]. Despite its excellent history as a P source, its use has declined as other P fertilizers have become more popular.
Liquid fertilizer solutions and fluid fertilizers are popular in many areas because they’re safe to handle, convenient to mix with other nutrients and chemicals, and are easily applied. A solution of urea [CO(NH₂)₂] and ammonium nitrate [NH₄NO₃] containing between 28 and 32 percent nitrogen (N) is the most popular fluid N fertilizer.
High crop yields often come under scrutiny because of the fertilizer levels needed to produce such yields and because of the perception and reality of the potential environmental impacts of those inputs.
Despite phosphorus (P) availability from geologic deposits distributed around the globe, widespread P deficiency in soils limits the growth and productivity of plants in many parts of the world. Because of this, growers commonly add this nutrient to their fields to improve crop yield and quality. Polyphosphate is an excellent liquid P fertilizer used to increase agricultural production.
Scientists from Arizona State University compared fluid ammonium polyphosphate (10-34-0) applied in irrigation water with granular monoammonium phosphate (MAP) broadcast and irrigated into the soil as phosphorous (P) sources for high-yield alfalfa (eight cuttings per year) and to study movement and availability of P in a calcareous soil.
When it comes to phosphate source selection, the menu is a good one. It contains liquid sources, such as the polyphosphates 10-34-0 and 11-37-0; and granular sources such as monoammonium phosphate (also called MAP, which is 11-52-0) and diammonium phosphate (also called DAP, which is 18-46-0).