Diammonium phosphate (DAP) is the world’s most widely used phosphorus fertilizer. It’s made from two common constituents in the fertilizer industry, and its relatively high nutrient content and excellent physical properties make it a popular choice in farming and other industries.

Production of Diammonium phosphate(DAP)

Ammonium phosphate fertilizers first became available in the 1960s, and DAP rapidly became the most popular in this class of products. It’s formulated in a controlled reaction of phosphoric acid with ammonia, where the hot slurry is then cooled, granulated and sieved. DAP handles and stores well. The standard nutrient grade of DAP is relatively high, at 18-46-0, so fertilizer products with lower nutrient content may not be labeled DAP.

The inputs required to produce one ton of DAP fertilizer are approximately 1.5 to 2 tons of phosphate rock, 0.4 tons of sulfur (S) to dissolve the rock, and 0.2 tons of ammonia. Changes in the supply or price of any of these inputs will impact DAP prices and availability. The high nutrient content of DAP helps reduce handling, freight and application costs. DAP is produced in many locations in the world and is a widely traded fertilizer commodity.

Agricultural use

DAP fertilizer is an excellent source of phosporus and nitrogen for plant nutrition. It is highly soluble and thus dissolves quickly in soil to release plant-available phosphate and ammonium. A notable property of DAP is the alkaline pH that develops around the dissolving granule. The ammonium present in DAP is an excellent nitrogen source and will be gradually converted to nitrate by soil bacteria, resulting in a subsequent drop in pH.

DAP or NPK is used while planting. These fertilizers are quickly and are immediately available to the plants depending on them to provide essential nourishment in the form of nitrogen, phosphorus and potassium. DAP Aand NPK fertilizers have a distinct advantage over organic choices, which depend on soil organisms to first break down the organic matter before nutrients can be released.

DAP and NPK are offered as dry granulesa and water-soluble powders. Controlled-release of these fertilizers dispense plant nutrients over an extended period from three to eight months, eliminating the need for repeated fertilizer applications throughout the growing season.

Management practices

Differences in the initial chemical reaction between various commercial P fertilizers in soil become minor over time (within weeks or months) and are minimal as far as plant nutrition is concerned. Most field comparisons between DAP and monoammonium phosphate (MAP) show only minor or no differences in plant growth and yield due to P source with proper management.

Non-agricultural uses

DAP also acts as a fire retardant. For example, a mixture of DAP and other ingredients can be spread in advance of a fire to prevent a forest from burning. It then becomes a nutrient source after the danger of fire has passed. DAP is used in various industrial processes, too, such as metal finishing. And, it’s commonly added to wine to sustain yeast fermentation and to milk to produce cheese cultures.