Calcium sufficiency strikes new low

A new yardstick for calcium levels in turfgrass soils has been established. Data show that calcium levels of 330 parts per million or higher (at pH levels of 5.5 to 6.0 or higher) should yield expected turf performance and allow superintendents to save dollars. The new soil guidelines, titled Minimum Level for Sustainable Nutrition (MLSN), were generated by Dr. Micah Woods, the chief scientist at Asian Turfgrass Center, working in concert with PACE Turf and its director Dr. Larry Stowell. The researchers discuss their work developing the new guideline in a video “Minimum Level for Sustainable Nutrition: The Calcium Guideline” now showing on YouTube.

Dr. Stowell said the effort to find a new recommendation level for calcium began with a question: “How can we do a better job of resource management in cutting the required nutrients down just to the minimum to maintain the turf at the expected performance levels?”

BCSR or Base Cation Saturation Ratios, which are noted in percentages (Ca%, Mg%, K%), are still used today and frequently over-recommend the application of calcium. But “we don’t think BCSR has a role any further in turfgrass management systems,” Dr. Stowell said.

SLAN or Sufficiency Levels of Available Nutrients is another guideline recommendation widely used today that finds calcium levels should be greater than 750 ppm.

 “We asked, how low can you go to maintain acceptable performance,” Dr. Stowell said.

Dr. Woods said, “I started thinking about this . . .because I kept seeing soil samples or nutrient levels in the soil where the levels of elements such as potassium, calcium and others were according to conventional soil recommendation guidelines . . . really low. But when we looked at the turfgrass performance--the quality of the grass, the health of the grass--the performance of the turf as a playing surface seemed very good. So here we are with levels in the soil that seem like they’re really low by conventional thinking about soil testing or interpretation, and yet the turf was performing extremely well. So I made some calculations of how much of an element is actually in the soil and how does that relate to expected turf uptake?”

Sharing data, Drs. Woods and Stowell created the new category of soil nutrient guidelines called Minimum Levels for Sustainable Nutrition or MLSNs. These guidelines focus on sustainability, reduced inputs and reduced cost of maintenance, all while maintaining expected turf performance. “We're not talking about compromising turf performance, we’re just talking about being smarter with the way the nutrients are utilized,” Dr. Stowell said.

Drs. Stowell and Woods recommend superintendents maintain a level of 330 ppm of calcium in the soil (while maintaining pH levels of 5.5 to 6.0 or higher to ward off aluminum/manganese toxicity). Higher amounts of calcium applied would not be as sustainable.

“The only problem with using the older SLAN or BCSR guidelines for calcium is primarily cost,” Dr. Stowell said. “So it doesn’t mean that you can’t grow good grass using SLAN or BCSR guidelines, it just means that you’re not getting the most out of your investment.”

Of his work Dr. Woods said he looks forward to “seeing lots more good performing turfgrass areas at a more sustainable level of calcium in the soil.”

The video “Minimum Level for Sustainable Nutrition: The Calcium Guideline” is the third-in-a-series of “Interviews with the Experts” videos produced by PACE Turf. Like other PACE Turf videos, this one is practical, to the point, and contains information that can be put to immediate use. PACE Turf videos can be placed on superintendent association websites or golf course websites by clicking on the “Share” button that appears underneath the video on YouTube. PACE Turf’s other golfer education and superintendent education videos can be viewed on the PACE Turf YouTube Channel or http://www.youtube.com/user/paceturf.

PACE Turf is a membership organization that provides breaking research news, information and expert advice on its website www.paceturf.org.  The mission of PACE Turf is to generate and share independent and objective agronomic information for turf professionals, so they may develop management programs that are effective, practical and scientifically sound.