Avoid Salt-Out of Liquid Fertilizers

Tacy Callies Tip of the Week


By Ajia Paolillo

The use of liquid fertilizers in citrus production has increased over the years. Liquid fertilizers offer the grower a way of applying frequent doses of fertilizer to trees to optimize nutrient efficiency.

Now that the winter months are here with cooler weather and some cold nights, growers may face the issue of liquid fertilizer salting-out in the holding tanks. The term salting-out refers to the fertilizer solids coming out of solution and forming crystals or sediment in the bottom of the tank. This typically happens to higher analysis liquid-fertilizer solutions when low temperatures occur. In many cases, the solids are difficult to mix back into solution, causing the fertilizer to not be as effective. In addition, the solids could cause clogging issues in the irrigation lines.

The temperature at which a fertilizer has the potential to salt-out is related to the chemical analysis, nutrient sources and the solubility of these materials in the solution. Different materials have different solubility rates, at different temperatures. It is important to remember that various combinations of nutrient materials will also change the temperature at which the solids in the fertilizer will begin to come out of solution and crystalize in the tank. If choosing to apply liquid fertilizer during the winter months, be aware of the potential for salt-out. Purchase fertilizer with formulations that are more stable during winter temperatures.

During cold weather, take these steps to help reduce the potential for clogging of the lines and emitters due to fertilizer salt-out:

  • Before running the fertilizer through the irrigation system, check the holding tank for signs of crystallization and sediment.
  • Agitate the liquid in the tank to attempt to dissolve the solids back into solution.
  • If the solids will not dissolve back into solution, wait until the weather is warmer and attempt agitation again. 

Ajia Paolillo is a University of Florida Institute of Food and Agricultural Sciences Extension multi-county citrus agent based in Arcadia.   

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