It is no surprise to anyone that water is vital for all of life and that you cannot successfully grow plants without it. Not all water is equal, however, and not all water is suitable for the vital task of plant irrigation. Depending on the source of your irrigation water, it could be full of biological or chemical impurities. It could have high levels of dissolved solids or heavy metals. The pH could also be too high or low for proper plant growth. It is important that you do not do more harm than good to your crops with your choice of irrigation water. while watering your crops.
It is no wonder that many growers utilize tap or well water since it is typically abundant and usually free or relatively inexpensive to use. These are fine options, especially if they are the only options, but any professional grower or commercial operation should additionally be purifying that same water for irrigation purposes. The quality of the water that keeps your plants alive is directly proportional to the quality, health, and robustness of the desired harvest. Impure irrigation water leads to unhealthy plants and poor harvests.
Water purity is especially important for hydroponically grown crops. Some soilless media, as well as garden or field soil, can act as a buffer for impurities that are found in many water supplies. In a hydro system, however, there is little, if not nothing to protect your plants’ roots from being exposed to whatever is in that water that can cause your crop undue harm.
Why You Should Purify Your Irrigation Water
Purifying irrigation water for your commercial grow rooms and greenhouses is crucial for several reasons, some intuitive, others quite technical. The use of impure water over time can clog irrigation systems, for starters. This leads to inefficiencies in water delivery and potentially uneven distribution of irrigation water. This is not even to mention the damage it can do to the physical system itself or its many components like lines and emitters. Using purified water will aid in consistent water flow to your crop plants and keep you from having to constantly clean or replace your irrigation components.
Residues in impure water can also build up in the plant’s vascular system. Plant tissue can accumulate contaminants over time. These accretions will negatively impact the taste, appearance, and ultimately, the market value of the end product.
Unclean and impure water can be contaminated with harmful pathogens. These could be bacteria, fungi, viruses, or even other unwanted biological residues. Traces (or larger quantities) of chemical contaminants could also be present in unpurified water. These could be pesticide residues, or heavy metals. Using purified water reduces the risk of crop damage or loss to these various contaminants, resulting in cleaner and safer harvested crops and heavier yields.
Impurities in some irrigation water can interfere with proper nutrient absorption by crop plants. Utilizing pure water will allow plants to receive the appropriate balance of nutrients to ensure healthy growth and higher yields. Water impurities can negatively affect desired pH levels which can also contribute to poor nutrient uptake by plants. Purified water will also help to avoid or minimize mineral buildup over time. Impure sources of irrigation water, such as tap water, can contain minerals that accumulate in various grow media over time, which can lead to nutrient imbalances and stresses to plants.
Not insignificantly, the use of purified water allows growers to maintain consistency, control, and in many cases, to achieve regulatory compliance. Purified water, by virtue of eliminating impurities that negatively affect the flavor, aroma, and overall quality of the crop, aids growers in the production of high-end, premium-grade harvests. This is due to the stable growing environment purified water helps to create throughout the entire cultivation cycle.
In many regions, irrigation water quality is subject to strict regulatory standards. These regulations are in place to protect the consumer and the safety of consumable products. Using purified water helps growers to meet these requirements and ensure compliance with regulatory standards. Even if there are no regulations where you operate, your irrigation water should still be as pure as you are able to get it.
Methods to Obtain Purified Irrigation Water
Now that we have established the importance of using purified water in a growing operation, let’s look at the various types of systems and methods that can be used to obtain it. Options range in price and complexity, but there are numerous products on the market that can be plugged into any sized operation.
Activated Carbon Filters: Activated carbon filtration absorbs and traps most organic compounds, and many chemicals that can be present in impure water. These are not usually used as the sole purification system for most growers, but are usually used in conjunction with another purification system. Activated carbon filters are especially good for removing or reducing unwanted odors and tastes from irrigation water.
Chlorination/Chemical Treatment: Chemical treatments, most often chlorination, involve adding disinfectants like chlorine, directly into the irrigation water, usually through an injector or other device that can regulate the delivery of the chemicals, in order to kill bacteria and other pathogens in the water. Careful monitoring of any chemical or chlorination system is critical as residual compounds can cause safety issues if not managed through proper dosing.
Filtration Systems: Numerous types and styles of filtration systems are available on the market, but they all essentially perform the same function in the same manner. They use physical barriers such as sieves, screens, mesh, ceramics, even sand, to remove particles, sediments, and other debris from water. Like the activated carbon filters, these are often used in conjunction with other water purification methods and are generally used as the “first line of defense” of purifying water as they improve the clarity and protect against clogs in the equipment. This method, though, is not useful for removing all chemicals and dissolved contaminants that can be found in some irrigation water.
Ion Exchange Systems: Ion exchange systems purify water by removing dissolved nutrient ions, such as calcium (Ca), magnesium (Mg), and sodium (Na) using resin beads. Then, as the name implies, these ions are exchanged with other ions. These systems are primarily used in applications where water hardness needs to be addressed to reduce or prevent scale buildup in irrigation delivery equipment.
Ozone Water Treatment: Ozone water treatment works by injecting ozone gas (O3) into water to oxidize and remove impurities like bacteria, viruses, and other organic matter. While very useful in disinfecting water, often used to improve the odor and color of water, ozone treatment systems are often used in tandem with other purification systems because they don’t remove sediment from the source water.
Reverse Osmosis (RO) Systems: Reverse osmosis technology is very commonly used in many commercial growing operations. RO systems utilize a semi-permeable membrane that the source water is forced through in order to remove minerals, salts, and other contaminants. These systems are highly effective at producing pure water with low levels of Total Dissolved Solids (TDS).
UV Sterilization Systems: Ultraviolet sterilization involves the use of UV light to disinfect water by killing bacteria, viruses, and other microorganisms. These systems effectively kill biological contaminants, but are not able to remove dissolved solids or chemicals, so these systems are also often employed as one part of a total solution for commercial growers to purify their irrigation water.
Water Sources
After looking at the importance of purified water and several systems and options to achieve it, the original source of the irrigation water should not be overlooked. Choosing a water source is a very crucial decision to make when opting to grow premium and high value crops. The cleaner the water is to start with, the easier it will be for any purification system or method to achieve the desired levels of purification for your crops. In many cases, growers are more or less stuck with what comes out of the tap, whether it is public or well water, but there are many other considerations when choosing a source.
While arguably the most widely available source of water, tap water (municipal or “city” water) should not be used to directly irrigate plants if at all possible. Tap water quality and attributes vary wildly throughout with wide-ranging pHs, levels of hardness, and it often contains additives like lime, chlorine, and/or fluoride. Tap water can be used as the primary water source for irrigation if it is subjected to one or more of the purification systems mentioned above. Even then, it is better to let tap water sit for a day or so before using so that sediment can settle and some of the chlorine can evaporate.
Well, cistern, or reservoir water is often also used for irrigation, especially outside of urban areas. The quality of this kind of water varies wildly. It generally contains mineral content, like tap water, but may also have any number of other contaminants that have leached into it, such as chemical insecticides, or fertilizers residues. These sources of water also need to be regularly monitored for bacteria, fungi, viruses, and parasites. A water quality analysis should be performed prior to considering well or reservoir water to be used on your plants. Correct any deficiencies, and then make sure it is purified before being used. Chlorination is one of the most common treatments for well water, even for residential uses.
Growers who are situated near rivers, streams, or other natural (or man-made) waterways can be understandably tempted to use this free source of abundant water. As with well and tap water, the quality of the source water varies greatly. It too can have chemical residues, biological wastes, and harmful pathogens. Depending on where the river or stream is situated, mineral composition of the rock material that is passed over needs to be accounted for. Rivers or streams in urban areas are likely to be more contaminated than those in more rural or pastoral settings, but these areas are likely to contain more farm runoff, than in urban areas which are more likely to have heavy metals present and other chemical wastes that have leached from the soils or landed in the water from asphalt or concrete runoff. If river or stream water is your only option for irrigation water, take it from as high an elevation as possible, have it tested regularly, and then purify it before using it for your crops.
Rainwater is arguably a cleaner source to start with than any of the previously mentioned types. It usually has far fewer impurities and biological contaminants than river or stream water. It also tends to have a stable pH around 7 or just below. This source is of course only practical if you have the means to collect and store it (and it is legal to collect where your operation is), as well as if you live or operate in an area that gets sufficient amounts of rain to warrant collection of it. Prior to its use, it should be purified to be safer to irrigate with, before applying it to your crops.
If it is an option, bottled mineral water is a better choice for irrigation, though this is usually cost-prohibitive on a commercial scale. Its benefits are low ECs, stable pH, helpful minerals, and no contaminants. Bottled water with lower mineral contents, though, are generally better for irrigation.
An even cleaner source of H20 that is often overlooked, but again, is not as practical for commercial growers, is air conditioner water. Water pulled from the air in the process of air conditioning is essentially distilled water. It will still need to be amended and purified as it can have a pH over 7.0 and may have some amount of EC depending on the age and condition of the air conditioner. Condition matters, because if there are rusty components that the water will make contact with then it can easily pick up some amount of unwanted metal debris, or other industrial materials that could harm your crops. The biggest benefit of air conditioned water is that it is a free source of relatively clean water, but will not water a large number of plants, unless collected and stored in bulk before purifying it to irrigate with.
The optimal source of water, that starts out pure, is distilled water. Purchasing and using distilled water eliminates the need for a purification system, but over time, the cost of the water would likely exceed the cost of a purification system if otherwise utilizing free or inexpensive water. The smaller the scale of production, the more practical using distilled water is. Distilled water has an EC of zero, so it is essentially a blank slate with which to add the precise level and amount of nutrients to your crops as you need. It does have a pH just over 7.0, so an acidic nutrient solution will likely be needed to counteract the higher pH.
In summation, the choice of which type of purification system or systems to use, along with the available type of source water (if there is a choice available), will be determined by each grower based on multiple variables such as:
- Initial water quality of the source water
- Desired level of purity
- Scale of the growing operation
- Specific requirements of the existing irrigation system
- Specifics of the strain or species of crop being grown
- Budgetary considerations of each individual grower or business
Using purified water is a necessity for operating a successful, growing venture.
Ultimately, armed with the knowledge that purified water leads to healthier plants and more robust harvests, as well as achieving regulatory compliance in some regions, each grower will likely land on some combination of source and system to achieve the desired results.
