A wise man once said, “There is nothing new under the sun.” This may be true, but some things can be overlooked.

What is most commonly overlooked when discussion soil fertility is calcium—more specifically, the form and application of calcium to your turf. It’s true that nitrogen, phosphorus and potassium are used in greater percentages than calcium, but no other nutrient is used more by weight and volume than calcium. In the soil, the relationship of calcium to other nutrients (e.g., magnesium, potassium and sodium) is dynamic, so to limit its importance to pH adjustment is short-sighted. Calcium is the second highest element percentage in plant tissue. Literally, then, calcium levels in both soil and plant are the backbone of an effective turf program.

In the soil calcium improves cation exchange capacity and soil structure by reducing compaction. This particularly benefits soil bacteria. Without the proper balance of calcium, soils become tight and restrict the flow of air and water, thus depleting beneficial microbes. Often soil imbalances come at the cost of calcium because of an increase in another nutrient such as magnesium, hydrogen or sodium. To correct this we apply gypsum or limestone in one of two forms: high calcium (calcitic) lime or dolomitic (high magnesium) lime.

It’s important to know if your soils are high in magnesium so you can determine which lime to apply. Applying dolomitic lime to a high magnesium level soil could create even more problems. Gypsum or calcium sulphate is another form of calcium but at times is misused. Unless your base saturation of calcium is greater than 60% the use of gypsum is not very effective. Once above this threshold the use of gypsum becomes an efficient way to knock off high magnesium and sodium levels or other excesses on the soil colloid without raising the pH.

Though calcium tends to make its own way in the soil, it is largely immobile and difficult for plants to utilize.

Even in calcium-rich soils with strong biological activity calcium does not solubilize well. In soils like golf course greens that are heavily managed and have high degrees of soil compaction, calcium’s mobility is even weaker. Though the application of gypsum is great for the soils calcium requirements, its efficiency (to the plant) is not as good as foliar applications, due to how long gypsum takes to actually become available to that plant. Calcium can be made more mobile from applications of ammonium sulphate which moves it from the soil colloid and into solution. This has been shown to aid in disease suppression but can also lower soil pH.

The benefits of calcium to the plant are numerous, primarily in root and cell wall development. Calcium enhances the strength of cell tissue for greater resistance to heat and heavy traffic stress and is the essential component (calcium pectase) for building strong cell membranes, proper cell division, cell bonding, overall plant vigor and stiffness. Stronger cell integrity makes for a stronger root system, and stronger cell membranes make for more aggressive rooting throughout the soil profile. Cell integrity is important in disease resistance, as research indicates that pathogens probe their way into a cell and inject their enzymes to weaken and eventually break the cell down. Thus, stronger cell membranes can actually slow or even stop this attack.

Because calcium also allows the plant to use sunlight, carbon dioxide, water, nitrogen and other minerals more efficiently and is essential in starch conversion, it makes sense to detect and correct calcium deficiencies both in the plant and in the soil early in the spring and continue applications through the growing season, as heat tends to exacerbate calcium loss. The new bentgrasses and lower mowing heights are increasing the need for calcium supplements for your plants. Strengthening what tissue is left surely will enhance the plants’ overall health.

Soil and tissue analysis play an important part in tracking your plant’s calcium levels. The standards offered in tissue analysis is a good place to start. There is still some discussion as to what calcium level in plant tissue is essential, since most standards are based on plants growing in “normal” conditions (including temperature) with “normal” traffic; however, the standards done for soils with the established protocols for balancing the basic cations, performed over 50 years ago by Dr. William Albrecht (University of Missouri) are still the optimums. His development of base saturations has been an invaluable tool.

Only after we’ve addressed the soil’s calcium and other nutrient levels can we focus on the plants.

In conclusion, when you sketch out your turf program this year and total nitrogen, phosphorus and potassium, remember to make a new column for calcium. It could be the edge your turf needs this summer.