Reclaimed Water May Affect Fertilization Needs

Reclaimed water is being used more frequently in the landscape.  It’s important to remember that reclaimed water has different properties than drinking water processed by our local water plants.  While it is perfectly safe to use, reclaimed water can have a higher salt and nutrient content than rainwater or drinking water.  If a property you maintain uses reclaimed water as its irrigation source, you should manage the landscape a bit differently.  Most importantly, you’ll want to test the water or otherwise obtain current test results so you know what level of salt and nutrients is being applied in the landscape.

From a landscape perspective, the most important item of interest is the nitrogen content in the water; it really varies in content from source to source.  Nitrogen is one of the main reasons we want to avoid over-fertilizing the landscape.  The use of too much nitrogen can stimulate excessive plant growth, encourage development of pest & disease problems, increase watering needs, encourage plant stress, runoff properties and pollute waterways, and waste money.  The great thing about nitrogen in your reclaimed irrigation water is that it’s like free fertilizer.  However, it’s important to know what is being applied through irrigation so you don’t over-fertilize.  This is often overlooked.

“Irrigation suitability” laboratory tests of reclaimed water are inexpensive and will provide important values and recommendations for fertilization.  Or, if you know the water’s nitrogen concentration, there are formulas available that can help to convert the nutritional content of reclaimed water into amount of nitrogen is being applied.  I’ve encountered some “mysterious” plant problems recently that I was able to trace back to excessive nitrogen applied through reclaimed water.  It’s not a problem to use this water source, but it is really important to reduce nitrogen applications to account for it.  Feel free to contact me with questions.


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