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Greenhouse Updates: Sep 9, 2016

Drought Information
Sep 9, 2016

The drought this summer has been a challenge for some growers. Many towns have water bans and some towns have discouraged new plantings. Some retailers have reported that the hot, dry weather has also reduced demand for plants. Depending upon the water source, another consequence of the drought may be the quality of water being used for irrigation. Equipment clogged with sediment (surface water), or high salt (Na and Cl) concentration in irrigation water due to low water levels are possible considerations.   

While likely sources of sodium (Na) and chloride (Cl) in the Northeast is road salt, water softeners and some fertilizers may also be contributors. High sodium acts to inhibit plant uptake of calcium, and may result in excess leaching of calcium and magnesium from the media. Acceptable levels of Na and Cl for ornamentals are  less than 50 ppm and 140 ppm, respectively, however higher levels may be tolerated depending on crop sensitivity. Na and Cl can be directly toxic to plants, may contribute to raising the soluble salts (EC) level of the growing medium, or may inhibit water uptake by plants. Plant problems include injury from excess soluble salts, growth reduction, and increased susceptibility to disease. Foliar chlorosis caused by high Na and Cl is similar in appearance to that caused by deficiencies of nitrogen, iron, and magnesium. If high levels of Na and Cl are suspected as plant problems, the suspicion should be confirmed by water testing.

A 2004 study of 50 Massachusetts greenhouse growers showed that most growers were irrigating greenhouse crops with water containing safe levels of EC, Na, and Cl. However, a small, but significant number, of growers were using water containing elevated levels of Na and Cl and accompanying high EC with the result being lower quality and even crop loss. Most often this water was from a private well or pond (usually near a road), but sometimes public drinking water was the source. With the current drought, it might be helpful to have water tested and test again prior to the spring growing season to prevent any potential problems.

The solutions to the problem of high Na and Cl include: Regular water testing during the growing season in borderline cases of excess Na and Cl and avoidance of over-fertilization to prevent high growth medium EC; installation of water treatment systems to remove Na and Cl; efforts to protect wells and ponds from salt contamination by runoff; mix existing water sources with collected water to dilute the high salts levels or, in extreme cases, finding a new source of water.


Northeast Regional Climate Center, Cornell University

UMass Extension Floriculture Water Quality Project: I. Salinity, Sodium and Chloride

UMass Extension Greenhouse Best Management Practices

MA DEP Municipal Water Restrictions in MA (Map)

State of Connecticut Water Status

UConn and Natural Resource Conservation Service (NRCS) Drought Project

Partial List of Water Testing Laboratories (for greenhouse water samples used by some growers)

Tina Smith, UMass Extension
with input from Leanne Pundt, UConn Extension