Super Journal: an online turf research resource
Super Journal is provided by PACE Turf as a free public service to the turfgrass management community. Our mission is to provide an electronic venue for:
- Superintendents to publish results of their turf research projects and to share them with fellow turf managers.
- Turf researchers to rapidly publish and disseminate their experimental results.
- Superintendents who want assistance in designing, carrying out, interpreting and/or summarizing turf research experiments.
Please see our submission guidelines if you wish to have your report published in Super Journal, and our research guide for information on designing and implementing your own turf research project.
A new look at calculating calcium requirements
We are continuing our efforts to refine the new Minimum Levels for Sustainable Nutrition (MLSN) guidelines in cooperation with Dr. Micah Woods at the Asian Turfgrass Center. In the process, we have received some questions about managing sodium.
The MLSN guideline identifies 110 ppm (milligrams/kilogram, mg/kg) sodium as the maximum threshold for cool season grasses. To maintain sodium below 110 ppm in the soil, supplemental calcium is sometimes needed. To determine how much calcium needs to be applied to reduce sodium if levels exceed 110 ppm, follow the calculations below. For a similar method using metric units, refer to the Asian Turfgrass Center calcium requirements in metric units:
- Determine how much excess sodium is present in your soil by subtracting 110 ppm (mg/kg) sodium (Na) from the value on your soil report.
For example, if your soil contains 150 mg/kg sodium, your soil contains 40 mg/kg more (150 mg/kg - 110 mg/kg) sodium than is desired.
- To compute how much calcium is needed to displace the sodium, we need to convert sodium units from mass into units of positive charge. To make the calculations easier, we use millimoles (mmol) of charge.
For example, (40 mg sodium/kg)/(23 mmol sodium charge/mg) = 1.7 mmol sodium charge/kg soil
- To displace 1.7 mmol sodium charge/kg with calcium, we will need 1.7 mmol calcium charge/kg soil
For example, (1.7 mmol calcium charge/kg) X (20 mmol calcium charge/mg) = 34 mg calcium/kg (ppm) are needed to displace the sodium
- To convert this value to pounds per acre, multiply by 2
For example, 34 ppm calcium X 2 = 68 lbs calcium/acre are needed to displace sodium
- To convert pounds per acre to pounds per 1000 sq ft, divide by 43.65
For example, (68 lb calcium/acre)/43.65 = 1.6 lbs calcium/1000 sq ft needed to displace 40 ppm sodium
- A shortcut to steps 2 - 5 is to multiply the excess sodium ppm value by 0.04 to obtain pounds calcium/1000 sq ft needed to displace excess sodium
- To determine how much of a calcium amendment is needed to provide the desired amount of calcium, divide by the proportion composition of the product.
For example, gypsum typically contains about 23% calcium. Therefore a requirement for 1.66 lbs calcium/1000 sq ft will require: (1.6 lb calcium/1000 sq ft)/0.23 = 7 lbs gypsum/1000 sq ft required to displace 40 ppm sodium
For example 40 ppm excess sodium x 0.04 = 1.6 lbs calcium needed/1000 sq ft
It is important to remember that calcium is also required as a plant nutrient (at levels of 330 ppm in the soil), in addition to its value as a tool for managing sodium. When calculating calcium requirements, you will need to keep both the sodium management and plant nutrition requirements in mind.
Minimum Level for Sustainable Nutrition
Increased economic and environmental pressures have caused many of you to re–assess the way you manage turf. With fertilizers as one of the bigger inputs, we felt that it was time to review and revise our current soil guidelines.
Working together with Dr. Micah Woods of the Asian Turfgrass Center, we reviewed data on all key soil nutrients from thousands of turf soil samples, and determined that in many cases, guidelines could be safely lowered without a dramatic impact on turf quality or playability.
The result of our efforts is the new "Minimum Level for Sustainable Nutrition" (MLSN) soil guidelines, a new, more sustainable approach to managing soil nutrient levels that can help you to decrease inputs and costs, while still maintaining desired turf quality and playability levels.
Additional information can be found here:
Calculating calcium requirements when sodium exceeds 110 ppm in the soil
STMA 2012
The resources below have been provided for participants of the 2012 Sports Turf Managers Association in support of the demonstrations provided by Dr. Larry Stowell of PACE Turf. Please conact us if you have any questions.
- Turf monitoring tools
- EC (electrical conductivity) monitoring for soil salinity
- Quick test for soil nitrate
- Interpreting soil analytical information
- Soil Chloride and Sulfur Guidelines
- Tissue Guidelines
- Water Guidelines
- PACE Turf disease photo index
- PACE Turf insect photo index
- How we review products and practices
- Links of interest
- Turfgrass disease diagnostic laboratories
- Soil analytical laboratories
- Fungicide combination products: decision making tools
- Turf growth potential in selected U.S. locations
- Turf growth potential at different average air temperatures
- Recycled Water
- IPM Planning Tools
- Precision Turfgrass Management
