Fertilizer Compatibility and Storage

Improper mixing and storage of fertilizers can result in large nutrient losses. Some important aspects to consider in fertilizer mixing and storage include the following:

• Urea should not be mixed with ammonium calcium nitrate (CAN), KCl, SSP or TSP.
• Urea can be mixed with most other fertilizers but fertilizer mixtures containing urea should be applied immediately after mixing. Do not store fertilizer mixtures containing urea.
• Ammonium phosphates and super phosphates should not be mixed with lime, slag, rock phosphate or CAN.
• Potassium chloride and sulfate of potash can be mixed with most fertilizers, but mixtures of these fertilizers with urea and calcium ammonium nitrate should not be stored.
• CAN should not be mixed with basic slag but can be mixed with urea, single superphosphate, and ammonium phosphates immediately prior to application.

Do not store fertilizers in damp or dirty places. Make sure that bags of fertilizer in the store do not absorb moisture from leaky roofs or water seepage through walls and floors.

Fertilizers tend to absorb water from the atmosphere (they are hygroscopic) and can become caked and almost cement-like and impossible to apply properly. Fertilizers will start to absorb water when the CRH is exceeded. Fertilizers that have a low CRH will absorb atmospheric moisture first (e.g., urea with a CRH of 70 will begin to clump together before SA which has a CRH of 79).