1999 Iowa Turfgrass Research Report

Objective: The objectives of the study are to determine the proper placement depth for Enkamat and to evaluate it as a stabilization material for sand-based systems.

Sand-based systems are widely used for sports fields to reduce compaction and promote rapid drainage. Sand is an excellent media for drainage of the rootzone, but it can result in an unstable surface, especially when the grass has worn away. New technologies are being developed to stabilize sand-based fields. Fibrillated polypropylene fibers woven into a synthetic black backing (SportGrass™), fibrillated fibers (TurfGrids^®), and interlocking mesh elements (Netlon, Ltd.) are a few of the products available for stabilizing sand-based athletic fields. Reinforcement material can be grouped into two categories: those that form a horizontal layer at or near the turf surface and those that are comprised of individual discrete units that are mixed into the rootzone layer (Baker, 1997).

Enkamat consists of a bulky mat made from nylon threads which are fused together where they cross. The thickness of this three-dimensional mat ranges from 11/16- to 7/8-inch and has an open construction leaving 90% of its volume to be filled with sand or soil (Baker, 1997). Enkamat has been used in combination with other geotextile material (polyester covers, TurfArmor®, and plywood) to protect the grass surface when special events are held on stadium fields.

Demonstration plots have shown that if Enkamat is exposed to the surface during field wear, there is a potential for tripping with cleated shoes. We are interested in how deep Enkamat needs to be placed to prevent exposure to the surface and if there is any benefit from field stabilization with Enkamat.

Methods:

A 50 ft. by 50 ft. sand-based pad, six inches deep, was constructed in the fall of 1997 for evaluation of Enkamat at the Horticulture Research Station, Ames, Iowa. The sand-based system was placed over a 4-inch gravel blanket with a network of 4-inch drain pipes. The sand rootzone is described below and no other physical amendments were added. The study area is automatically watered and is part of our new sand-based sports turf research facility. Table 1 shows the treatments that were installed to evaluate Enkamat as a reinforcement material for sand based athletic fields.

Table 1. Treatments used to compare the reinforcement capability of Enkamat on sand-based athletic fields.

Trt	Synthetic	Depth of synthetic below sod (sod contains 0.75 inches of soil)	Comments
1	Sand	--	Standard for the industry
2	Enkamat	0 (0.75 inches)
3	Enkamat	1 (1.75 inches)

The experimental design is a randomized complete block with three treatments and three replications. Individual treatment plots are 13 ft. by 16 ft. The large size of the plots will allow for study of an additional factor by sub-dividing each treatment plot. Potential split plot treatments could include typical field management factors such as topdressing or drill seeding. Enkamat will be placed at two different depths to ensure that it will not become exposed during intense traffic. We will determine if Enkamat provides any advantage for turf growth, even when placed deep enough in the soil profile to avoid surface exposure. Enkamat will be placed at two depths, even with the surface of the sand base or one inch below the surface of the sand base. In treatment #2, the top of the Enkamat is even with the top of the sand surface. When sodded, the top of the Enkamat is then covered by 0.75 inch of soil. In treatment #3, the top of the Enkamat is placed one inch below the surface of the sand. When sodded, the top of the Enkamat is then covered by 1.75 inches of soil. The study area was sodded on 7 November 1997 with ‘Midnight’ Kentucky bluegrass containing 0.75 inch of a Nicollet fine loam soil. Sod laid on sand based fields is the current standard for the industry. In northern climates, sand-based fields are seldom established from seed. Enkamat reinforced fields will need to show an improvement over the conventionally accepted sand fields that are sodded. Turf will be mowed, watered, and fertilized to simulate a high maintenance sand-based sports field. Turf will be mowed, without catching clippings, at a 1.5-inch height three times per week. Water will be applied through an automatic watering system at the first sign of wilt. Approximately 1.5 inches of water will be applied each week from May through September. Nitrogen will be applied at 1 lb N/1000 sq. ft./growing month. Phosphorous, potassium, calcium, magnesium, and micronutrients will be applied based on soil testing.

The study was evaluated for turf appearance, surface hardness, and traction from July through October. Turf appearance was evaluated by determining turf quality and percent turf cover. Surface hardness was measured with a 2.25-kg hammer attached to the Bruel and Kjaer 2515 Vibration Analyzer. The hammer was dropped from a height of 18 inches. Also, surface hardness was measured with a 0.5-kg Clegg impact hammer. Traction was conducted with a torque wrench apparatus attached to a cleated plate that was developed by Canaway and Bell, 1986. One hundred pounds was the load bearing weight of the torque device and the weight was dropped from a height of 2 inches. Traction was assessed as the amount of torque (N× m) required to tear the underlying sod. Traction data represent the average of two individual measurements per plot. From mid-August through October, traffic was applied every Monday, Wednesday, and Friday with a model T224 Brouwer roller that has been converted into a riding traffic simulator. Both of the two-foot-wide rollers on the traffic simulator are fitted with 5/8-inch football cleats on 2-inch centers. The rollers are attached by chain and sprocket to supply a differential-slip-type of traffic that produces a tearing action of the grass surface. During 1998, all Enkamat treatments received a total of 133 passes of simulated traffic. Soil moisture content was performed by randomly sampling soil cores from the study area on each of the four different dates. The soil moisture content was 10.69%, 17.21%, 10.57%, and 17.30% respectively for the four dates. The entire study area will receive both hollow and solid coring in 1999 to determine if Enkamat disrupts this routine management practice.

The Statistical Analysis System version 6.06 (SAS Institute, 1989) and Analysis of Variance (ANOVA) were used to analyze the data. Least Significant Difference (LSD) means comparisons were made to test between treatments effects on surface hardness (Tables 1 and 2), traction (Table 3), and turf appearance (Table 4).

1998 Results:

On 9 September 1998 Enkamat placed 1 inch below the sod resulted in a significantly harder surface than Enkamat placed immediately below the sod or the control without Enkamat when measured with the 0.5kg hammer (Table 1). This effect was observed in both the traffic and no traffic areas. Also, on 9 September 1998 the control treatment without Enkamat was significantly different between the traffic treated areas and no traffic treated areas when measured with the 2.25kg hammer (Table 2).

Enkamat treatments had no effect on surface traction, turf quality, and percent turf cover under conditions of no traffic or intense traffic. On 29 October 1998 turf injury resulted in a quality of 3 with 30 percent turf cover for the control and 35 percent turf cover for the treatments with Enkamat (Table 4). This level of loss resulted in approximately a 10 N·m decline in traction (Table 3). Traction was significantly less for the traffic treated areas compared to the non-trafficked turf.

Enkamat treatments did not affect traction in the traffic treated areas. Even though the turf was significantly worn, 30-35 percent turf cover, the sod layer was not "broken through" and the cleats of the traction measurement device did not contact the Enkamat. The traction device impacts a rotational force in a plane horizontal to the surface. It appears that this device does not simulate the forces necessary to cause breakthrough of the surface as observed when a player makes a foot-plant or sharp turn. There is currently no device available that measures field stability or the ability of a player to break through the sod surface. A visual but quantitative scale also needs to be developed to rapidly assess surface stability conditions.

Research will continue before a final report is prepared.

Literature Cited

Baker, S.W. 1997. The reinforcement of turfgrass areas using plastics and other synthetic materials: a review. International Turfgrass Society Research Journal, 8:3-13.

Canaway, P.M. and M.J. Bell. 1986. Technical note: An apparatus for measuring traction and friction on natural and artificial playing surfaces. J. Sports Turf Res. Inst. 62:211-214.

 

Enkamat Study Plot Plan

Objective: To determine required depth of placement for Enkamat.

Treatments:

1. No Enkamat

2. Enkamat 0" below surface of sand.

3. Enkamat 1" below surface of sand.

Installation procedure:

Table 1. Surface hardness measured with the 0.5kg hammer (g_max)

Treatment	7-24-98	8-25-98	9-29-98	10-29-98	Mean
NO TRAFFIC
Control - no Enkamat	80.3	84.0	74.7	59.3	74.6
Enkamat - 0 inch below	77.3	76.0	73.7	61.7	72.2
Enkamat - 1 inch below	81.0	80.0	86.3	60.7	77.0
TRAFFIC
Control - no Enkamat	88.0	90.0	87.3	62.3	81.9
Enkamat - 0 inch below	86.0	82.0	83.7	64.7	79.1
Enkamat - 1 inch below	86.7	85.0	98.3	64.7	83.7
LSD(0.05) =	ns	ns	8.9	ns	5.3

NS = not significant at P æ 0.05.

Table 2. Surface hardness measured with the 2.25kg hammer (g_max)

Treatment	7-24-98	8-25-98	9-29-98	10-29-98	Mean
NO TRAFFIC
Control - no Enkamat	53.7	53.0	54.3	51.7	53.2
Enkamat - 0 inch below	55.7	55.7	58.3	52.3	55.5
Enkamat - 1 inch below	53.0	52.3	64.0	54.0	55.8
TRAFFIC
Control - no Enkamat	55.0	57.3	67.0	51.3	57.7
Enkamat - 0 inch below	57.0	57.7	63.7	50.7	57.3
Enkamat - 1 inch below	54.0	53.0	73.0	50.0	57.5
LSD(0.05)	ns	3.8	10.3	ns	ns

NS = not significant at P æ 0.05.

Table 3. Traction measurements (N·m)

Treatment	7-24-98	8-25-98	9-29-98	10-29-98	Mean
NO TRAFFIC
Control - no Enkamat	52.3	46.7	48.6	49.9	49.4
Enkamat - 0 inch below	52.8	48.1	48.3	49.8	49.8
Enkamat - 1 inch below	50.4	46.6	52.5	49.7	49.8
TRAFFIC
Control - no Enkamat	50.6	49.8	49.4	39.3	47.3
Enkamat - 0 inch below	54.6	50.6	48.2	38.4	47.9
Enkamat - 1 inch below	51.6	48.3	49.7	38.3	47.0
LSD(0.05)	ns	ns	ns	2.2	ns

NS = not significant at P æ 0.05.

Table 4. Percent turf cover (% cov) and turf quality (Q), 10 = best and 1 = worst.

Treatment	7-24-98			8-25-98		9-29-98				10-29-98		Mean
	Q	% cov	Q		% cov		Q	% cov	Q		% cov		Q	% cov
No Traffic
Control &emdash; no Enkamat	8	100	9		100		10	100	10		100		9	100
Enkamat &emdash; 0 inch below	8	100	9		100		10	100	10		100		9	100
Enkamat &emdash; 1 inch below	8	100	9		100		10	100	10		100		9	100
Traffic
Control &emdash; no Enkamat	8	100	9		100		6	55	3		30		7.7	71
Enkamat &emdash; 0 inch below	8	100	9		100		6	50	3		35		7.7	71
Enkamat &emdash; 1 inch below	7	100	9		100		6	55	3		35		7.7	72
LSD(0.05)	ns	ns	ns		ns		ns	ns	ns		ns		ns	ns

NS = not significant at P æ 0.05.

ISU Horticulture:Publications:1999 Turfgrass Report

College of Agriculture