'But Would it Make a Good Drink?'
Richard W. Bosley, Mentor, Ohio
Water has many functions within a plant and so it's quality is a very important consideration for a grower. Water acts as a bio-chemical reagent, a solvent, a transport agent, a heat regulator, the hydraulic fluid for plant support, and some of it becomes a part of the plant cell. All life depends on water. The qualities that make water suitable for human use may not make it suitable for plant irrigation.
A restaurant that I frequent has a planter with some tropical plants which only retain the top leaves as the lower ones have been burned off by high salts. They water these plants with tap water. The source of the tap water is Lake Erie, which is good, then through the city chlorine treatment, which is good, but when it comes into the restaurant it goes through a softener and this is where the trouble is. They feel the need to soften it so it will make good quality coffee but the sodium used in the process is poison to the plants.
Several years ago we were having trouble with our azalea propagation which was showing up as the roots turning brown and the leaves yellowing after being under mist for two to four weeks. After having the water analyzed we found that the well which had been good for 40 years had turned salty and could not be used for mist propagation in which the salts are concentrated because of the constant evaporation from the leaves and medium surface. Our choice was to switch to city water which had proved, by test, to be very low in soluble salts and thus very good for plants.
This will not always be the case though with city water. In the Los Angeles basin they use water that has come from the Colorado River and is so high in soluble salts that it makes the growing of petunias difficult. To grow a good quality azalea you must de-ionize water first and then add back the fertilizer you wish which makes the water very expensive. Let us look at what soluble salts are, how we can test for them, what to do if you get them, and what to do before you buy that new "farm".
What Are Soluble Salts?
I am sure that most of you have heard of the "U. C. System" but what you might not realize is that the soil mix is only a small part of the system. If you do not already have a well worn copy of this "Manual 23" I suggest you send a dollar to:
Agriculture Publications
University Hall University of California
Berkeley, CA 94720
The reason that I suggest this is that they have a very good section devoted to the problems of salinity in the nursery which is well worth the price alone. California growers learned long ago about water quality because of the nature of their water sources but it is only recently that water quality problems are starting to pop up in the areas of "pure" water such as the Pacific Northwest and the eastern growing areas. Soluble salts are any chemical compounds which are dissolved in the soil water solution. This would include those minerals needed for plant growth but may also include such things as sodium chloride which probably is the item injuring the plants in the restaurant I mentioned earlier.
The growing plant root tip acts as a membrane and when presented with this soil solution the dissolved minerals will seek to equalize their strength on either side of the membrane
even if this means withdrawing water from the plant
. The plant does not have the ability to select only those minerals it wishes and only in the desirable amounts so that when presented with a high soluble salts situation, plant tissue injury is inevitable.
The older leaves will be the first to be injured as the
new leaves
have the top water priority and are the last to be damaged. By the time you see leaf injury, extensive root damage has already occurred but it might not be too late to leach heavily. Something in the order of one foot of water per six inches of medium would bring the salts out.
How to Test for Salts
A very large grower who might have his own laboratory may choose to purchase a Solubridge and make extracts of saturated soils to test for high salts. In most cases it would seem like more reliable results would be achieved from sending a sample of questionable water or soil to a commercial laboratory or your State Cooperative Extension Service for suitable testing. It would be an excellent practice for a rower to test his critical water sources at least once a year. It is also a good idea to test your line irrigation water AFTER FERTILIZER INJECTION OCCURS for soluble salt concentration to make sure the injector is working properly.
What To Do If You Have Salty Water
If you have recognized that you have a problem the first thing to do would be have it tested by a reputable agriculture laboratory. Re sure that the laboratory gives you a recommendation along with the results, as to the quality, and if possible how you might improve it. Water that might have too much salts. depending on what salts are present, for mist propagation might be acceptable for irrigation if you are careful. Light watering tend to concentrate salts at the soil surface where evaporation occurs but if watering is adequate to always get some leaching, marginal water might work. If mist propagation is being used it is very important to use good quality water. Since the volume employed is relatively low a person could afford to purchase water in bulk loads and store it or tie into city water if that is available. Rain water might be another possibility. Be sure to check whatever source you might choose to substitute for your deteriorated well.
What To Do Before You Buy The New Farm
It is not unusual for you to have soil tested before purchasing a new piece of property on which you will be growing nursery stock but don't forget to have the water tested also. Water is something that many of us have taken for granted but today with increased population and industry. the use of water, whether from the ground. a pond, or stream may not be a constant value. The wise grower will find it is a good investment to test his water sources at least once a year.