What is in irrigation water? Is it good, bad or undesirable? What do we test for? How do we test? When do we test? What does it all mean?
These are questions that are often proposed at water quality seminars because water chemistry can be a very complex science: The contaminants are numerous — with even common contaminants posing problems — and the technologies used for treatment compound the complexity. Every water supply is different to some degree, and water testing on different sources varies if the water comes from a well, pond, lake, river, cistern, reclamation system or municipal supply.
Additionally, each water supply offers different contaminants and associated problems, plus treatment options vary extensively. Too many times, growers wait until there is a problem before correcting a situation: It is always better and less costly to be proactive than reactive, and this is where testing helps control larger problems.
Well water is the most problematic because of iron, manganese, calcium, magnesium and organics that cause nutritional problems and staining. These waters can cause numerous aesthetic issues and pose concerns with disease.
Water that tests negative for E-coli and coliform, which are indicators of pathogenic presence, can still test positive for heterotrophic plate counts (HPC). HPC can cause disease problems in roots and other problems where bacterial contamination provides a food source.
Even municipal water supplies, which are dosed with chlorine, can cause microbial growth because of phosphates added to the water as a sequestering agent used to prevent scaling. Algae seem to be the biggest factor in these municipal water issues, since the phosphate breaks down and offers microbes a food source.
The problem with high alkalinity is the change in soil media. The pH rises in the media over time and affects the plant’s growth and overall production time. Acid can be injected into the water to control this problem or special media can be used to combat the rise in pH. This is where an in-house test can help the grower get real-time test results so treatment can be implemented and changes made to subdue any production maladies. Proper pH and alkalinity can help nutrients absorb into the plant better and keep hardness minerals and iron in suspension, which reduces scaling and staining.
Growers can also test for specific nutrients such as iron or even trace minerals like copper or boron that affect growth of certain varieties. Again, an in-house test can give instant results, and fertilizers can be adjusted. Many times, growers scout their plants for symptoms, take samples, send them to labs and await results before applying the remedy. This results in lost time and even lost production and plant mortality: It is easier to grow a healthy plant from the start and keep it healthy than turn a crop around after it has had days or weeks of poor nutrition. Trial and error methods are not cost effective.
Common tests for most growers are pH and bicarbonate alkalinity. The biggest influence on testing would be the origin of the water, and it must be stressed that each source is worlds apart. Each type of system has simple, inexpensive, in-house test equipment that can create peace of mind for growers. Water treatment devices that are implemented into operations must be functional and monitored on a daily, weekly and monthly basis.
Bacterial tests need to be performed on waters that are drawn from nearly every supply. Each source would need specific monitoring depending on the type of supply. Water drawn from a pond would need to monitored more often than water from a well, and depending on the treatment technology, this monitoring would also need to be adjusted. Chlorinated systems should be tested to make sure the water is getting proper disinfection and there is not a breach in equipment performance. UV systems need to be watched closely because the quartz sleeves can scale, reducing UV output and efficacy. Ozone systems need to be tested or have inline monitors in place to assure system integrity.
Setting up in-house testing can be very simple and inexpensive. There are many titration test kits that are easy to use and cost effective. There are also test strips that cost only pennies per test. These tests are not as accurate as lab results but can help set a baseline from which growers can make solid judgments and decisions.
Spectrophotometers are more accurate and pricey, but the costs to set up multiple tests can actually offset the initial startup. There are various makes, models and brands on the market, and each offers a higher level of accuracy. Some of these products are able to test to very low levels of certain contaminants, and the parameters tested can be as high as 90-100. These units are durable and portable for easy use and long life.
Growers need to address water quality like they do soil media. Analyze the incoming water closely when applying a treatment process and then monitor the water to be sure the treatment is working effectively. We check the oil on our cars and other equipment, and water treatment equipment should be no different. Preventative maintenance is always better and most times less costly than repairs, lost time and production. Keeping close tabs on water quality can help make the difference of a successful crop or a failure.