Michigan State University Extension
Soils & Soil Management - Fertilizer - 06209712
07/10/97
Fluid Fertilizers--Liquids and Suspensions MSU Ag Facts Extension Bulletin E-933, December 1984, Revised, destroy previous editions
by R. E. Lucas and M. L. Vitosh, Department of Crop and Soil Sciences
Nitrogation and fertigation are terms sometimes used to describe the application of nitrogen or other fertilizer nutrients through an irrigation system. The most common fertilizer applied is a 28 percent nitrogen solution because it is easily obtained and causes few or no problems when added to the water. All soluble dry products, such as urea, ammonium nitrate and potassium nitrate, can be dissolved in water and then metered into the irrigation system. Phosphate materials, anhydrous ammonia and aqua ammonia should not be applied through an irrigation system because of precipitation problems and losses of ammonia into the air during application.
The amount of nitrogen that can be applied through the irrigation system is limited only by the capacity of the injector pump. Even with a high rate of injection, the nitrogen will be so dilute that it will not injure crops. Most situations call for rates of 20 to 50 pounds of nitrogen per acre per application.
Many greenhouse operators and vegetable growers are equipped to apply fertilizer through their watering systems. They generally make up a concentrated solution and dilute it 100 to 300 times with water through an injector. Many strive for a final concentration of about 100 ppm nitrogen in the water. Twenty ounces of 20 percent nitrogen fertilizer added to one gallon of solution and then injected into the water at a ratio of 1 to 200 will make a final solution containing 150 ppm nitrogen.