Features Agronomy
Sodium, bicarbs impact role of soil

Sodium and bicarbonates in the soil are a “big deal” and can rob golf courses of their nutrient dollar, superintendents attending BrettYoung’s annual spring turf academy were told in March at the Links of Kent Golf Club in Chatham, Ont.

Greg Moore, distributor sales manager for Plant Food Company, said knocking back sodium to make all nutrients more available to turf and dissolving bicarbonates to make calcium more available is imperative.

Sodium compacts soil, decreasing nutrient availability.

“Sodium is the bad boy of turfgrass management,” he said.

The good news is that available soil calcium can reverse that, he added. Making calcium soluble to displace sodium is “the big deal,” he added, noting bicarbonates found in irrigation water is what prevents the calcium from doing its job.

“It’s taking it out of the game.”

Bicarbonates decrease calcium availability and decrease nutrient availability to the roots. If soils are high in sodium, superintendents need to ensure there is enough total calcium present in the soil, which can be determined by a soil test. If soil calcium levels are low, the tendency is to put out regular products because it’s more cost effective as long as the product dissolves quickly. Once there is sufficient calcium, it must solubilize. This is when long lasting acids work well. If there is sufficient rain, there is no need for additional acid products because rain is acidic by nature and releases calcium, making all nutrients more available.

“Soil testing is the pink elephant in the room,” Moore said, adding everyone should be testing and know what to do with the results. Many, however, don’t use the test results because they don’t know how to extract the information.

Moore said a turf plant compares to the engine in a truck. The soil is the transmission that works with the engine to allow one to get to where he wishes to go. A superintendent can have the best turf variety, the best nutrient program and the best aerification program, but if the soil is out of balance it’s like driving down Highway 401 in third gear, he said. One can still reach his destination, but he’ll end up overworking his engine and will experience an uncomfortable ride “because your soil transmission is not working properly.”

Soil tests reference what is present in the soil, but not what is needed. The big three nutrients that plants require are nitrogen, phosphorus and potassium while the big three nutrients needed in the soil are calcium, magnesium and potassium. As the “soil transmission mechanic,” the superintendent needs to make sure all nutrients are available.

When the goal is to make all nutrients available, Moore said the soil biology, soil structure and soil chemistry must all be considered. The biology includes putting out good organic matter to feed the microbes that produce more nitrogen, phosphorus and potassium. Attention to the soil structure includes building a green properly and making sure aeration is done to get oxygen into the soil. The focus on soil chemistry works with the biological and physical components.

Moore said sodium breaks down soil structure, rendering it tight. When irrigating, greens will start to puddle. Even a small amount of sodium could make clay particles tight and prevent water penetration. Roots will lack oxygen and become shorter. High amounts of sodium make it difficult for the plant because all nutrients become less available, prompting superintendents to put down more nutrients to compensate.

“Poor soil chemistry can be very expensive and puts more stress on the plant and puts more stress on you when you’re trying to get excellent playability conditions. High sodium can be a problem.”

Calcium to cure sodium problem
When high sodium levels are present, the cure is having enough calcium, magnesium and potassium in the soil that is soluble. Moore said the cure is available calcium and not total calcium.

“If I have calcium and sodium, calcium is always going to win.”

Sodium has one charge and an atomic weight of 23. Calcium has two charges and an atomic weight of 40.

“If calcium is available, it will beat sodium, but sometimes calcium becomes unavailable and is busy someplace else.”

Clay soils tend to present issues with sodium, and even a small amount can be detrimental. Sodium acts like glue, and its one charge makes the clay particles stick together. In high sodium soils, the clay sticks together, preventing air and nutrients to move through. This happens when sodium levels typically increase in the summer. Greens tend to puddle when irrigating.

If there is available calcium and it’s watered in, it solubilizes the sodium. The calcium knocks out the sodium, and calcium’s two positive charges takes the clay’s negatively charged particles and inverses them.

Moore said if irrigation has taken place for three or four weeks and nutrients are becoming less available and puddles are occurring, and then a rain storm occurs that initiates green-up and water is beginning to move better, it’s because the calcium is solubilizing and opening up the soil.

Available calcium will displace sodium, Moore said, but bicarbonates in poor irrigation water can cause sodium buildup. Bicarbonates in water for human consumption is good, but if a water test shows bicarbonates are more than 120 parts per million, it’s undesirable for irrigation. In bottled drinking water, bicarbonate levels are 285 parts per million.

“If you irrigate with bottled water, you would have less nutrients available to your turf.”

Even though bicarbonates are good for humans and pets, they present issues when their levels in irrigation water are high.

“If your bicarbs are 120 or over, I would be concerned. Below that, you have plenty of solubility.”

A water test will provide a sodium adsorption ratio (SAR). If the number is greater than four, there is an issue, Moore said. If it’s less than four, there is more calcium and magnesium than sodium that allows things to be available.

He shared a water test example in which the SAR was 1.48, suggesting plenty of calcium and magnesium present in the water. But the bicarbonate level was 249 parts per million – greater than the ideal level of 120 – indicating it could make the calcium unavailable. If there is ample rain, it won’t be an issue, he said, but during a dry season with frequent irrigation and a bicarbonate level greater than 120, more can be done.

Bicarbonates have a physiological effect on roots that leads to a reduction in nutrient adsorption. High bicarbonates lead to unavailable calcium, elevated sodium levels and nutrient tie-up. The problem with bicarbonates is that when there are high levels, calcium cannot displace sodium. Combined with soil calcium, the calcium becomes unavailable. Sodium levels are able to increase, locking up the soil and decreasing the efficiency of fertilizers.

Moore said superintendents reading a chemical extraction test should pay particular attention to the percentage of sodium present as well as the levels of calcium, magnesium and potassium.

A saturated paste test will determine proper availability. A three-point priority will determine if there is a need to solubilize more of the calcium in the soil. The percentage of potassium must be greater than that of sodium. Potassium is the barrier that keeps moisture in the plant. Sodium dehydrates nutrients and moisture of the cell wall. The percentage of calcium must also be greater than the sum of the percentage of magnesium and the percentage of potassium. Calcium should be at least 40 parts per million.

“If any one of those three fail, you need to solubilize with an acid or pray for rain.”

Moore said the cure for dissolving bicarbonates is to use acids, and acid rain delivered by Mother Nature will also do the trick. Acid injection systems are effective and have been successfully used “for ages” in Florida where there are significant bicarbonate issues. Long-lasting acids work in the soil for 21 to 28 days to release calcium and knock out sodium.

“Acids are a fantastic tool to release things.”