If you are a greenhouse grower then you are most likely familiar with the importance of proper water quality for your crops. Water quality can easily be determined by taking measurements periodically. It is important to use accurate and reliable equipment to perform the measurements. A wide selection of high quality conductivity testers and hydroponic pH testers can be found here at an affordable price.
To determine the suitability of water for irrigation you can easily take measurements of the Electrical Conductivity (EC) and the Sodium Adsorption Ratio (SAR). In general, the higher the EC and SAR, the less suitable the water is for irrigation. Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil.
SAR measurements are provided with laboratory analysis of the water. However, EC measurements can be made using a portable EC meter. The Myron L AG6/pH was specifically designed as a pH and conductivity tester for greenhouse crops.
As a rule of thumb, the water is considered borderline and its use can present problems if conductivity values are higher than 0.8 millisiemens/cm (mS) and SAR is over 4. If the conductivity measurement is below 0.8 mS and the SAR measurement is below 4, the water is suitable for greenhouse irrigation. Particular management practices should be used when water is outside the acceptable limits. This might include using a growing medium with excellent drainage, leaching with every watering and compensating the sodium with calcium and magnesium.
If galvanized steel is used throughout the greenhouse and water is reclaimed for irrigation, it is a good idea to check the amount of Zinc in the water and make nutrient correction accordingly.
Many greenhouses use drip irrigation systems, which are efficient and low maintenance, but nozzles can become clogged by hard water. Check for high levels of bicarbonates (above 100 ppm) in the water and neutralize with the appropriate acids.
There are many factors that affect water quality and greenhouse crop growth. Consult your fertilizer manufacturer for recommendations on proper nutrient levels.