Difference Between DAP and NPK Fertilizer

The key difference between DAP and NPK fertilizer is that the DAP fertilizer has no potassium whereas the NPK fertilizer contains potassium as well.

What is DAP Fertilizer?

DAP fertilizers are sources of nitrogen and phosphorous that have wide usage in agricultural purposes. The major component in this fertilizer is diammonium phosphate that has the chemical formula (NH4)2HPO4.  Moreover, the IUPAC name of this compound is diammonium hydrogen phosphate. And it is water-soluble ammonium phosphate.

In the production process of this fertilizer, we react phosphoric acid with ammonia, which forms a hot slurry that is then cooled, granulated and sieved to get the fertilizer that we can use in the farm. Moreover, we should proceed with the reaction under controlled conditions because the reaction uses sulfuric acid, which is dangerous to handle. Therefore, the standard nutrient grade of this fertilizer is 18-46-0. This means, it has nitrogen and phosphorous in the ratio of 18:46, but it has no potassium.

Typically, we need 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 for the production of DAP. Moreover, the pH of this substance is 7.5 to 8.0. Therefore, if we add this fertilizer to the soil, it can create an alkaline pH around the fertilizer granules that dissolve in soil water; thus the user should avoid adding a high amount of this fertilizer.

What is NPK Fertilizer?

NPK fertilizers are three component fertilizers that are very useful for agricultural purposes. This fertilizer acts as a source of nitrogen, phosphorus and potassium. Therefore, it is an important source of all three primary nutrients that a plant requires for its growth, development and proper functioning. The name of this substance also expresses the nutrient that it can supply.

NPK rating is the combination of numbers that gives the ratio between nitrogen, phosphorous and potassium provided by this fertilizer. It is a combination of three numbers, separated by two dashes. For example, 10-10-10 indicates that the fertilizer provides 10% of each nutrient. There, the first number refers to the percentage of nitrogen (N%), the second number is for phosphorous percentage (in the forms of P2O5%), and the third is for potassium percentage (K2O%).