ammoniated superphosphate

Definition

Fertilizer produced by mixing ammonia with superphosphate in the ratio of 5 parts to 100.

Agricultural Uses

Ammoniated superphosphate is a powdered or granulated grey material with an acid odor.
To 9.1 kg of phosphorus (in the form of P₂O₅), 2.7 to 3.2 kg of ammonia is added. Where concentrated superphosphate is used, 2 kg of ammonia is added for every 9.1 kg of phosphorus.
Ammoniated superphosphate contains 2 to 6% nitrogen and 6 to 21% phosphorus (14 to 49% P₂O₅,, Ammoniation of superphosphate offers an inexpensive way of adding nitrogen to a fertilizer, which reduces the water-soluble phosphorus content to less than 20% in ordinary superphosphate whereas nearly 50% in triple superphosphate. Nitrogen promotes phosphorus uptake by plants by (a) increasing the tip and root growth, (b) altering the plant metabolism and (c) increasing the solubility and availability of phosphorus. Ammoniacal fertilizers facilitate absorption of phosphorus better than nitrate fertilizers do.
Ammonium superphosphate becomes easy to store when made free-flowing by mixing with non-caking agents like limestone, sand, rice hull, granite dust, kaolin clay or tobacco stems. It is not effective as a fertilizer for wheat and rice in laterite soil, but gives higher response in black cotton soil, alluvial and calcareous soils. Similar to ammonium phosphate sulphate, ammoniated superphosphate forms an acid in the soil. In humid regions, soils develop acidity as a result of leaching, erosion and crop removal. This feature is being used successfully even in low fertility agricultural soils.