Cation Ratios and Soil Testing Methods for Sand-Based Golf Course Greens

Rodney St. John, Nick Christians, Henry Taber

This research is being supported by a grant from the USGA.

Introduction:

The current recommendation for golf course greens construction is to utilize a sand root-zone mix. These sands have low cation exchange capacities (CEC), ranging from less than 1 to 6 cmol_c•kg^-1. With so few cation exchange sites available, applying the correct amount of fertilizer to provide adequate plant nutrition without causing nutrient leaching can be difficult. To further complicate the problem, the sand used for greens and athletic field construction is often derived from limestone and is termed calcareous. Calcareous sands are found throughout the United States.

Calcareous soils have been extensively studied on agronomic crops established on soils with large proportions of clay, silt and organic matter and relatively high cation exchange capacities. Very little work has been done to relate turfgrass growth and development with the low CEC-sands used for golf course greens.

Goal:

To develop a set of standard methods and models to be used in analyzing turfgrass soil samples, especially for calcareous sand samples. To gain better understanding of cation ratios used for making fertilizer recommendations. Accurate recommendations will help develop best management practices that increase overall turfgrass health and protect the environment.

Objectives:

1. To evaluate and correlate several existing soil extraction methods with tissue analysis to determine which type of extractant is best for sand based turfgrass systems.
2. To modify, if necessary, existing extraction methods to better suit turfgrass soil types.
3. To better understand how the BCSR theory and Ca/Mg/K ratios apply to turfgrass systems.
4. Improve current recommendations for Ca/Mg/K fertilization of turfgrass.

Research Methodology:

Soil Testing Methods:
A greenhouse experiment will be started to evaluate different extraction methods and gain further knowledge about different Ca/Mg/K ratios. Four different levels of each Ca, Mg, and K will be applied to creeping bentgrass established on calcareous or silica sand. Soil and tissue samples will be taken and analyzed for nutrient content using an Inductive Coupled Argon Plasma (ICAP) machine, which can analyze 12 different nutrient concentrations. The different extraction methods will be correlated with tissue analysis and applied fertilizers.

Moreover, tissue and soil samples will be collected from several golf courses and other turf areas with varying soil type, and the soil testing methods will be correlated with tissue tests.

Ca/Mg/K Ratios:
The same greenhouse experiment listed above will try to establish different basic cation ratios. Some preliminary work will be done to determine the best methodology for establishing and maintaining the different cation ratios. As of now, we are planning to use 4 different levels of each Ca, Mg, and K to make 12 different cation ratios. Creeping bentgrass will be established on either calcareous or silica sand. Clippings and soil samples will be collected and analyzed monthly. Tissue, soil test results, and quality ratings will be correlated to evaluate the differing cation ratios.

Treatments

• One Grass: creeping bentgrass
• Two Sand Types: calcareous and silica sand
• Three different nutrients: calcium, magnesium and potassium
• Four different levels of each nutrient: low, medium low, medium high and high

Expected Results:

Initiate or develop use of better analysis techniques for soil nutrient testing of sand-based turfgrass systems.
Improved understanding of Basic Cation Saturation Ratio Theory and Ca/Mg/K ratios used for fertilizer recommendations.

ISU Turfgrass:2003 Turfgrass Report

College of Agriculture

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