AgriBoost - as a Golf Course Putting Green Construction Material
Dr. Wayne R. Kussow, Douglas J. Soldat
Department of Soil Science – UW Madison

All research is sponsored by ASI Specialities, Ltd. and all rights are reserved. Any use of this
information without the expressed written consent of ASI Specialities, Ltd. is prohibited.

MATERIALS AND METHODS

During the fall of 2001, a putting green was built to USGA specifications at the O.J. Noer Turfgrass Research and Education Facility in Verona, WI. The green is comprised of twenty 6 ft. by 8 ft. cells consisting of 12 inches of root zone mix overlying a pea gravel blanket with imbedded drain pipe. A plywood grid and plastic sheeting extending the full depth of the root zone physically isolates each cell. The cells are arrayed in 4 rows of 5 cells each. Each row of cells constitutes a replicate of randomly located treatments.

The treatments are root zone materials of different compositions. Included are: (1) pure sand; (2) sand + AgriBoost (Jordanian zeolite); (3) sand + GSA ZK406H (a U.S. zeolite); (4) sand + Profile (a porous ceramic material); and (5) sand + peat moss. The ratio of sand: amendment in the mixes is 90:10 (v/v). Each cell was outfitted with a well for insertion of TDR probes at 5 different soil depths for moisture measurement and a low-tension lysimeter for leachate collection (Figure 1). A cover was placed over the green to minimize wind erosion and contamination of the root zone mixes during the winter months.

Figure 1

The root zone mixes were prepared by measuring out the volume of sand required, pacing it in a windrow on a paved surface, and spreading over the windrows the proper volume of amendment. These were then blended by making several passes thorough the windrow with a tractor- mounted compost pile mixer (Figure 2).

Figure 2

The putting green will be seeded to L-93 creeping bentgrass (Agrostis palustris Huds) in mid-May of 2002 or when the soil temperature reaches an acceptable level. The surrounding banks will be sodded with Kentucky bluegrass. Following seeding, a grow in period will take place. Once the grow in period is complete, the green will be placed under an irrigation, mowing, fertilization, and disease control program typical of that of an up-scale Wisconsin golf course.

Plant parameters such as density, quality, green speed, clipping weight, clipping nutrient content, rooting depth, root mass density, disease incidence and severity, and localized dry spot will be measured at varying frequencies. These tests will characterize treatment effects on bentgrass grow in, its subsequent growth, nutrition, and putting green quality. These plant responses will eventually be related to the physical and chemical properties of the root zone materials.

Detailed records will be kept of all construction costs, and any factor that has an influence on the economic and environmental benefits that may accrue from use of the various root zone amendments. Such factors are time to putting green playability, sustained turf quality, fertilizer, water, and pesticide requirements. This information will serve as the basis for treatment cost/benefit analysis. Relevant physical and chemical properties of the root zone construction materials and mixes are currently being measured in the laboratory. The following section provides a summary of the data collected over the past five months.

RESULTS AND DISCUSSION

Particle Size Distribution:
The first objective of the lab analyses was to verify that the field blended root zone mixes were as uniform as can be expected and are the intended 90:10 (v:v) blends. To do this, laboratory root zone mixes were carefully prepared in small batches using a twin shell blender. The carefully blended lab mixes were compared to the field mixes.

The particle size distributions of the laboratory and field mixes were very similar (Table 1) suggesting that the compost pile mixer used was an effective tool for creating uniform root zone mixes. There was some concern that AgriBoost, which has a wide range of particle sizes, would not yield a mix that meets USGA pecifications. While the AgriBoost amended mix did have higher percentages of very fine sand and silt + clay than in the other mixes, the mix does meet USGA standards of <10% fine gravel and very coarse sand, >60% coarse and medium sand, and < 10% very fine sand + silt and clay.

Table 1: Particle size distribution of root zone mixes prepared in the lab and in the field

Lab Samples - Root Zone Mixe

Field Samples - Root Zone Mixes

pH values:

The CaCl2 and H2O soil solution pH values of the root zone mixes and the amendments are
listed in Table 2. The pH was run in a 0.01 M CaCl2 solution because this more closely
approximates field pH of a fertilized putting green.

Table 2: Water and dilute salt solution pH values of the root zone mixes
and mix amendments.

The AgriBoost mix had the highest pH (Table 2) followed by GSA, Profile, and peat moss respectively; the pH of each root zone mix was dominated by the pH of the sand. This sand like many others used around the U.S. for putting green construction, contains a yet to be determined amount of carbonates.

Cation Exchange Capacity:

Compared to the minerals commonly found in soils, zeolites have a unique property. Due to the nature of their crystalline structures, many of the negative charged sites in zeolites can be accessed by cations such as NH4 + and K+ that have small hydrated radii (< 5A.), but not by large cations such as Ca2+ and Mg2+, whose hydrated radii are 9.6A and 10.8A respectively. This can be a very important distinction from the perspective of N and K management in sand based putting greens. The NH4 + and K+ bonded to the sterically restricted sites in zeolite are not subject to displacement by Ca2+ or Mg2+ and will therefore, suffer much lower leaching loss as compared to root zone mixes that do not contain zeolite.

To verify the existence and magnitude of the preferential bonding of NH4 + and K+, the cation exchange capacities of the root zone mixes and amendments were determined via Ca2+ saturation/Mg2+ displacement (Figure 3) and NH4 + saturation/K+ displacement methods (Figure 4).

Figure 3

Figure 4

One thing that is important to note, is that the cation exchange capacity measurements are taken on a weight basis while the root zone mixes are created strictly by volume measurements. Therefore, the peat moss appears to have a relatively high cation exchange capacity as an amendment, but loses much of that benefit when incorporated into a 90:10 (v:v) root zone mix. Peat moss has a much smaller weight to volume ratio than any of the other amendments used in this study. Another important property of peat moss is demonstrated by these two experiments. Peat moss is capable of retaining relatively large amounts of divalent cations, but retains very few monovalent cations such as NH4 + and K+ on its exchange sites. We see this when the cation exchange capacity of the peat moss changes from 24.16 cmol kg-1 when divalent cations are used to 1.54 cmol kg-1 when monovalent cations are used.

When the ammonium/potassium method was used, the estimated cation exchange capacity of each zeolite (AgriBoost and GSA ZK406H) increased roughly five times from that obtained using the calcium/magnesium method. The other inorganic amendment used in this study, Profile, showed almost no change in cation exchange capacity from one method to the next indicating that all negatively charged sites in the product are equally accessed by monovalent and divalent cations. The pore spaces in the zeolite act as an ionic sieve, letting the smaller ions (in this case ammonium and potassium) pass, while denying the larger ions access to many of its exchange sites. It should be noted that although AgriBoost and GSA ZK406H are both zeolites, AgriBoost demonstrated a CEC of almost twice that of GSA.

Moisture Release Data:

Soil cores were prepared for the moisture release measurements by compacting them to the degree of a severely compacted putting green. While this is the standard laboratory method used for evaluating putting green root zone mixes, it represents a worst-case scenario and most likely does not represent the field conditions that would be found in a new putting green.

Obtaining moisture release data is a very lengthy process. Approximately six weeks are required to obtain one moisture release curve. Fortunately, we have the equipment to measure up to ten curves simultaneously. The data included in this report are incomplete (Figure 5). Data is currently being collected for the release curves of duplicate samples. The trends we are seeing so far indicate that the AgriBoost root zone mixes retain moisture just below that of the peat moss mixes, and above the remaining three treatments. However, statistically significant differences cannot be calculated until data collection is complete.

Figure 5

SUMMARY

AgriBoost has demonstrated a cation exchange capacity far superior to that of the other amendments tested. It has shown a special selectivity for smaller cations such as K+ and NH4 +. This property may very well lead to agronomic, economic, and environmental benefits from using AgriBoost as an amendment to a sand-based root zone. Its ability to hold a large amount of water and release it at a relatively low tension is also a very desirable trait with probable significant benefits.

REFERENCES

1. Amrhein, C., and D.L. Suarez. 1990. Procedure for determining sodium-calcium selectivity in calcareous and gypsiferous soils. Soil Science Society of America Journal. 54:999-1007
2. Schofield, R.K. 1949. Effect of pH on electric charges carried by clay particles. Journal of Soil Science. 1:1-8.
3. Hummel, Jr., Norman W. 1993. Laboratory methods for evaluation of putting green root zone mixes. USGA Green Section Record. March/April 1993. 23-27.