Q & A WITH DR . GRADY MILLER

Our irrigation water was recently tested and found to be slightly salty . This situation is all new to me . Is there anything we can do considering that this is our only irrigation water source ?

Good water quality is often taken for granted , but like the soil you use , irrigation water should be periodically tested to see what is in it . Water may be found unsuitable for a particular use based on selected chemical and biological characteristics . Salts , sodium , bicarbonates , pH and other minerals affect water quality . Water quality is also not static , but may be influenced by a number of situations . For example , pumping and depletion of groundwater can cause saltwater to migrate inland and upward , contaminating the water supply .

Salty water ( also called saline water ) can cause leaf burn for turfgrasses . Salt water in the soil can pull water from the plant ’ s roots , resulting in physiological drought stress , even with adequate moisture in the ground . If the concentration of some salts is high enough , there can be a direct ion toxicity to the plant , resulting in poor plant health . Another potential problem from salty irrigation water can be ion imbalances that can result in nutrient deficiencies .

There are also significant negative implications of salinity to the soil . Salty water will degrade soil structure , causing more compaction and reducing pore space for water movement . Without adequate water movement through the profile , surface ponding of water will reduce efficacy of fertilizers and pesticides . The compacted soil profile can also negatively impact the soil ’ s microbial ecology , which is necessary for good plant health .

The salinity hazard of water is usually expressed as the total content of soluble salts , measured by electrical conductivity ( EC ) or total dissolved salts ( TDS ). These units are used to classify irrigation water quality so that management practices can be suggested for different levels of saltiness of the water . At the lower end of the scale , there is usually little concern since periodic rainfall will dilute the salt water . As the saltiness of the water increases , there is an increased

need to leach the salts from the soil by using additional water , either from the same source or from a cleaner source . I suggest you contact a water specialist if your water tests above 1,000 ppm total salts . They can determine a leaching program for you to use if needed .

Salts and sodium do not act independently . For that reason , water quality tests will usually measure the sodium adsorption ration ( SAR ) to determine the ratio of sodium to calcium and magnesium . This ratio will also be used to classify irrigation water and help determine the potential damage sodium will inflict on soil structure and permeability . In general , an SAR value below three is considered very safe for turfgrasses . Water with an SAR of nine will cause increasing structural damage to clay soils and then to sand soils with slightly higher SAR values .

Gypsum is the first line of defense to use for soils with high SAR values . Research has started evaluating other amendments that may be helpful when using poor water quality for irrigation . Some of these amendments may be injected directly into the water and others may be applied to soil . Cultural practices such as cultivation and topdressing can be used to improve soil properties . Ultimately , you will likely need to more closely manage your other inputs to try offsetting any negative influences from the water . SFM

Grady Miller , Ph . D . Professor and Extension Turf Specialist North Carolina State University

Questions ? Send them to Grady Miller at North Carolina State University , Box 7620 , Raleigh , NC 27695-7620 , or e-mail grady _ miller @ ncsu . edu

Or , send your question to Pamela Sherratt at 202 Kottman Hall , 2001 Coffey Road , Columbus , OH 43210 or sherratt . 1 @ osu . edu

50 SportsField Management | March 2023 sportsfieldmanagementonline . com