How Important is Water Testing?

It’s important to know what your plants are constantly coming in contact with. Your water is H2O plus whatever micronutrients and macronutrients are in your water source- which can vary significantly. All of these materials will have an effect on your nutrient solution formulation and need to be considered, especially with respect to adjusting magnesium levels. Depending on your water quality, you may also need to use Cal-Mag if your water is too pure (RO water) and plants are showing deficiency signs (especially if cultivating in coco coir).

Testing Greenhouse Water Supply

Greenhouse water sources should be tested thoroughly prior to constructing a greenhouse. Existing producers should test water at least twice a year in summer and winter to ensure that adjustments can be made in consideration of seasonal changes to mineral salt levels, pH, and alkalinity. Should groundwater sources become contaminated, regular water testing will ensure that contamination is identified before toxins can be taken up by plants and passed on to expose consumers. Water quality can also be monitored on-site with pH, TDS (dissolved minerals), and EC meters for more simple measures and day to day adjustments.

Laboratory Tests for Water Quality

  • Inorganic Elements
  • Electrical Conductivity (EC, soluble salts)
  • pH
  • Alkalinity
  • Nitrate Nitrogen
  • Levels of Calcium, Magnesium, Sodium, Potassium, Phosphorus, Zinc, Copper, Aluminum
  • Levels of Pesticide and Herbicide, and Fuel Oil Contaminants
  • Microbial Contaminants and Pathogens

What to Test Water For

For greenhouse production, four water test parameters are recommended: pH, alkalinity, hardness, and electrical conductivity (EC). You can regularly test your pH and EC using your pH/EC meter. Testing for alkalinity tells you what your water’s “buffering capacity” is (ability to neutralize acids). If you need to correct pH, you will need a product like pH Up or pH Down. Water with alkaline compounds requires more acidity to be added to balance it.

You can test for alkalinity and water hardness yourself using DIY kits or get a sample tested for irrigation purposes at a lab inexpensively. Lab water tests are typically much more elaborate and will include levels of many elements in parts per million (PPM). You check your results against acceptable limits for trace elements on the UMass website.

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