Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, September 9, 1993 TAG: 9309090167
SECTION: CURRENT PAGE: NRV-13 EDITION: NEW RIVER VALLEY
SOURCE: Joe Hunnings
DATELINE: LENGTH: Medium
More than likely, the focus will be on how human activity has adversely affected a river, lake or other body of water.
In fact, I have even written about how you - the home gardener - can have a negative impact on water quality through improper use of fertilizers and pesticides and unsound soil management.
Many of us also are concerned about drinking water quality.
But have you ever thought about the quality of the water you use to water your gardens and houseplants?
If not, let me try to "wet" your appetite for more information.
I have been hearing a lot lately about water quality:
How does the "quality" of the water affect my plants?
Is it OK to use my regular (drinking) water for my plants?
When we talk about water use for plants, an important water quality factor is the amount of soluble salts (total dissolved salt content) it contains.
The dissolved salts usually found in water include sodium (Na+), potassium (K+), magnesium (Mg++), calcium (Ca++), chloride (CI-), nitrate (NO3-), sulfate (SO4-) and bicarbonate (HCO3-) ions.
When water in the soil contains excessive soluble salts, plant roots are damaged, making them unable to properly absorb water and nutrients.
Tolerance to dissolved salts varies with plant species and age - young plants are less tolerant of high salts than older plants.
The soil's moisture level also affects the accumulation of salts - water salinity increases as rainfall decreases.
If you want to know about the soluble salts in your water, test it with a conductivity meter. Accurate meters are relatively inexpensive and easy to use.
Elements normally useful to plants sometimes can be toxic.
For example, boron and nitrates - when present in the soil in high amounts - can cause leaf burn, root damage and reduced seed germination.
Metals normally tied up in an alkaline soil, such as iron, manganese, zinc and copper, can become toxic when the soil solution becomes acidic.
Fluoride sometimes produces plant damage on foliage plants, like dracaena and chlorophytum. It also can reduce the longevity of gerbera, freesia, rose and gladiolus cut flowers.
Usually, the amount of fluoride in a municipal water supply is not enough to cause damage to plants.
Potted plants with a soil pH below 6.0 can be damaged by excessive fluoride because of the fluoride found in perlite and superphosphate, used in potting mixes.
Hardness of water refers to the calcium and magnesium present. Hard water contains carbonates and bicarbonates.
At low concentrations, they are merely annoying, plugging up small irrigation tubes and spotting foliage that's been watered overhead.
As their amounts become greater, they form insoluble compounds with other elements, making the nutrients unavailable for plant use.
High levels of carbonates and bicarbonates also interfere with floral preservatives used to condition fresh cut flowers.
Many homeowners use water softeners to alter the hardness of their water.
Water-softening replaces calcium and magnesium in the water with sodium. Water treated this way is not recommended for plant irrigation because the sodium level is too high for plants and may cause damage.
It's better to use rainwater or another water source to irrigate your plants.
Water quality also can affect other aspects of home gardening.
For instance, you should always read the label before mixing pesticides.
Some pesticides cannot be mixed with alkaline water or a reaction called alkaline hydrolysis occurs, causing the active ingredient in the pesticide to decompose or lose effectiveness.
If you know the pH of your water is too alkaline, you can adjust it to a neutral pH before mixing the water with a pesticide.
Joe Hunnings is the Virginia Cooperative Extension Service agent for agriculture in Christiansburg. If you have questions call the Montgomery County extension office at 382-5790.
by CNB