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What Does DAP Mean When Talking About Fertilizers?

By Hallie Engel ; Updated September 21, 2017
A farmer is throwing fertilizer on his crops.
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Diammonium phosphate is a widely used phosphorus-based fertilizer. Rich in nutrients, it's been available since the 1960s and is created by combining sulfur, ammonia and phosphate rock, which are heated or treated with acid. Heat-treated DAP fertilizer is more pure and is cooled and processed into grains before it's ready to use.

Composition of DAP

DAP fertilizer is widely used in the agricultural industry. In order to be labeled as DAP, it must meet the standard grade of 18-46-0, which refers to the available levels of nitrogen, phosphate and potash, according to the International Plant Nutrition Institute. As it's nutrient-dense, a little DAP fertilizer goes a long way, and it's also easy to store and handle, making it an affordable choice in comparison to other products.

Importance of Phosphorus

The phosphorus in DAP fertilizer, which is highly water-soluble and easy for plants to absorb, aids in protein synthesis, cell division and the development of new plant tissues. Using DAP fertilizer in soil lacking available phosphorus also helps plants to mature, strengthens their roots and improves hardiness, according to the University of Nebraska-Lincoln. If plants lack phosphorus, they grow poorly, are prone to insect damage and have difficulty surviving cold winter weather.

Nitrogen Needs

DAP fertilizer is also a rich source of nitrogen, which is vital to strong, healthy plants. Nitrogen aids in energy transfer and is also present in chlorophyll, which helps plants perform photosynthesis and create their own food from sunlight. Without nitrogen, plants experience weak growth and cannot produce strong, healthy seeds and fruit. Too much nitrogen is also problematic, though; for instance, tomato vines and leaves grow rapidly with too much nitrogen but produce fewer tomatoes.

Using DAP Fertilizer

Wear a dust mask and goggles when working DAP fertilizer, as it can irritate your mucous membranes and eyes. DAP fertilizer should be blended with soil to a depth of approximately 8 inches. Amounts vary depending on what you're growing. After using DAP fertilizer, the soil will temporarily have an alkaline pH of 8.5, so test the soil using a store-bought kit before planting to ensure it's returned to the pH level that's right your crops. Store DAP fertilizer in a cool, dry area away from water and light.

Other Uses

There are various uses for DAP fertilizer outside of agriculture, from metal finishing to food. Wine and cheese are often made with DAP, as it provides nutrients to yeast and bacterial cultures, aiding the fermentation process. DAP fertilizer can also be mixed with other substances and spread over woodland to prevent forest fires while enriching soil and plants.


About the Author


Hallie Engel is a food and lifestyle writer whose work has appeared in several international publications. She served as a restaurant critic for "Time Out Abu Dhabi" and "Time Out Amsterdam" and has also written about food culture in the United Arab Emirates for "M Magazine." She holds a bachelor's degree in communications and film studies from University of Amsterdam.