Report to the Stapledon Memorial Trust

Evaluation of rootzone mixes and water retentive amendment materials in sports surface constructions

Dr. Stanislav Hejduk Department of Animal Nutrition and Grassland Management, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic [email protected]

Details of the fellowship

Contact in UK: Dr. Stephen W. Baker Sports Turf Research Institute St. Ives Estate Bingley West Yorkshire, BD 16 1AU [email protected]

Research and Fellowship Dates: 9 August – 8 October 2010

The main Purpose of the Fellowship was to undertake a research project to investigate the use of various organic and inorganic rootzone amendment materials to improve both water retention and surface stability.

Research Report

INTRODUCTION Sand-dominated rootzones are now widely used for high quality sports facilities because of their good drainage properties, greater air-filled pore space after compaction and more consistent playing characteristics, particularly in respect to the firmness of the surface (Adams 1986, Baker 1989).

Two of the potential problems associated with sand-dominated media are ensuring adequate water and nutrient retention. Accordingly, amendment materials are regularly added to the sand material and there has been a considerable amount of research on the effect of different amendment materials and application rates for sports turf rootzones (eg. Waddington et al. 1974, Cook & Baker 1998, Baker et al. 1999, Baker et al. 2010).

There has, however, been relatively little research work on the effects of the depth of the amended layer on water retention properties of rootzones. There is a need to assess whether it is better for the amendment material to be applied through the whole profile or concentrated in the surface layers where most of the root system is found.

It is also important to be able to predict the potential implications for water retention, particularly within the main rooting depth of the grass plant, when a specific amendment material is used. Laboratory data can be obtained relatively easily for different combinations of amendment materials and incorporation rates. The laboratory tests can give water release curves which indicate the volume of water retained at a range of moisture potentials (SWB papers with water release curves, ASTM F 1815-06). Knowledge of the water release characteristics of rootzone materials should give a relatively easy method of predicting water retention of different amendment materials through the depth of the profile.

The objectives of the current study were therefore:

1) To assess the effects of a number of amendment materials and the depth of incorporation on water retention within typical profiles used for sports turf construction.

2) To examine how effectively water release curves can be used to predict the vertical distribution of water within sports turf rootzones.

MATERIALS AND METHODS The study was carried out under laboratory conditions using 150 mm diameter plastic cylinders. Within each column, a profile was constructed with a 300 mm rootzone layer over a 50 mm gravel drainage layer. The rootzone was based on uniform medium sand (Table 1) and the gravel was a fine gravel where all particles fell within a 2-5 mm size range. The gravimetric moisture of the sand was 4.7 %. The sand and gravel coincided with the normal ranges for golf green construction (STRI 2006, Baker 2006).

TABLE 1: Particle size distribution of the used sand

Category Particle diameter (mm) % Coarse gravel 3.4-8.0 0.0 fine gravel 2.0-3.4 0.2 Very coarse sand 1.0-2.0 2.1 Coarse sand 0.5-1.0 52.2 Medium sand 0.25-0.5 41.4 Fine sand 0.15-0.25 2.9 very fine sand 0.053-0.15 0.4 silt+clay under 0.053 0.9

Experimental design A randomised block design was used with three main treatments: profile characteristics, amendment type and amendment rate. a) There were three profile arrangements. All contained the amendment at the appropriate rate in the upper profile (0-150 mm) but for the lower profile (150-300 mm) three alternatives were included, i.e. amendment at the same rate as the upper profile, amendment at half the rate of the upper profile and no amendment in the lower profile (sand only). b) Five amendment materials were used as follows:

Sphagnum peat (commercially available material)

Composted green waste (Re-do, Bathgate Silica sand)

Zeolite (Clinoptilolite, grade 0.5-1.0 mm, Zeocem Inc., Slovakia)

TerraCottem Turf (mixture of hydroabsorbent polymers of acrylamide and acrylic acid, partially neutralized by potassium and ammonia salts, humic acids and zeolite, TerraCottem n.v. Belgium)

Stockosorb M (cross-linked potassium polyarylate/polyacrylamide co-polymer, grade 0,8 – 2.0 mm; The Resource Management Group, Inc. Atlanta GA 30350)

Three rates were used for each material, nominally 0.5, 1.0 and 1.5 times a typical rate for each material based on either earlier research or manufacturer’s recommendations). Rates of 10, 20 and 30% by volume were used for the two organic materials and the zeolite. For the TerraCottem the recommend rate was 600 g m-3 and for Stockosorb 1200 g m-3. A control with no amendment was also included. All combinations were included using three randomised blocks.

Preparation of the profiles Each column was 375 mm high and had a voile membrane attached at the base and was supported on a perforated plastic mat to allow free drainage and ease of handling. The 50 mm drainage gravel was added to the base of the column and then the lower rootzone (including any amendment as appropriate) was added in two layers, each of 75 mm. Each layer was consolidated using four blows from a 2.82 kg weight dropped from a height of 0.39 m (packing energy for each layer = 2.5 kg m-2). After each compaction treatment, the upper 5 mm was lightly raked to prevent layering and any adjustments to the height of the layer were made to give the desired 150 mm depth. The upper rootzone was then added again in two layers with the same compaction treatments to give a total depth of the rootzone of 300 ±10 mm. The rootzone finished 25 mm from the top of the cylinder allowing space for water to be ponded in the cylinder as part of the wetting procedure.

The mixes were prepared with moist sand (gravimetric water content approximately 5 %). To saturate the cylinders, 2650 cm³ of water (50% of the total rootzone volume) was added and the materials were left overnight. A further 2650 cm³ was added the following morning.

Photo 1: Cylinders filled with different rootzone mixtures

Measurements To monitor changes in water content during drainage, volumetric water content in the upper 60 mm was measured using a Theta probe. Initial measurements were made within the first minute after the ponded water had completely percolated into the surface of the rootzone. Further measurements were made after 1, 2, 4, 6, 24 and 48 hours. In all cases, three replicates were made per cylinder.

After gravitational drainage for 48 hours, the surface was lightly compacted (one blow of the 2.82 kg mass from 0.39 m) to firm the surface after the theta probe measurements. Hardness was then measured again using a Clegg soil impact tester (0.5 kg test mass released from 0.55 m. Three measurements of peak deceleration during impact were made per cylinder. After the hardness measurements, shear strength was measured using a Geonor shear vane fitted with four blades of 50 mm length and 12 mm width. Measurements were made in the area of impact from the hardness measurements as these areas had more uniform consolidation because of the greater compaction.

To determine the bulk density and the volumetric water content after gravitational drainage, the columns were excavated in increments of 50 mm. The exact height of each layer was recorded and the total weight of material removed was determined. A sub-sample of around 100-150 g was taken for measurement of gravimetric water content after drying at 105˚C. Bulk density was calculated as the dry weight of material per unit volume, and volumetric water content for each layer was calculated from bulk density x gravimetric water content.

Water release characteristics Samples were taken from each rootzone for determination of hydraulic conductivity measurements and water retention measurements using USGA methods (ASTM F 1815-06). The range of tensions was extended to give a sequence of 10, 20, 30, 40, 50 and 60 cm tension. Measurements were taken after 24 hours at each tension.

Photo 2: Water release characteristics measurement on a tension table

Statistical analysis Statistical analyses were performed using ANOVA (Statistica 7.1, StatSoft) with a randomised block design where all the treatments were analysed separately.

Results and discussion

Water retention

Individual amendment materials increased water retention in a rootzone unevenly. The greatest water retention was measured for the 30% sphagnum peat and the 1.5 recommended rate of Stockosorb (Table 1). Both these treatments increased water retention in the rootzone top layer (150 mm) almost by 150% compared with pure sand (36 mm at Stockosorb rate 1800 g m-3, 35.5 peat 30% vs. 14.6 mm at pure sand). The lowest water retention was recorded for the Terracottem amended rootzones, even when added at the highest rate (17.9 mm at 1.5 RR). Average water consumption of turfgrasses during summer sunny days in climatic condition of temperate zones is cc. 3 mm. Under these circumstances a 150 mm layer of pure sand would provide enough soil water for 5 days while the most retentive treatments could provide plants with water for 12 days. However, not all the water in rootzone would be available to plant roots. Part of this water is tightly bound on the soil matrix and is refereed to as „dead water“ and its content corresponds to permanent wilting point (PWP potential -1.5 MPa). Estimation of PWP is very time consuming and needs special equipment. Nevertheless, in sandy soils the value of PWP is very low but in amended rootzones this tends to be much greater. PWP values of the mixes will be estimated in laboratory in the Czech Republic which will allow the calculation of plant available water for each of the individual rootzones.

Water retention in the top layers 0 - 150 mm Vertical columns show confidental intervals at p = 0.95 45

waterretention (mm) 15

peat10 peat20 peat30

Terra10 Terra20 Terra30

Stock10 Stock20 Stock30

sand100

zeolite10 zeolite20 zeolite30 compost10 compost20 compost30

Figure 1: The differences in a water retention among individual rootzones in the top layer

The differences in water retention between the amendment treatments in the bottom layer of the profile (150 – 300 mm) are given in Figure 2. The difference between pure sand and the most retentive material is much smaller than in top layer. Water retention of pure sand is 40.0 mm but the most retentive rootzone with 1.5 recommended rate of Stockosorb contained just 59.0 mm of water which equates to a 47.5 % increase whilst this difference was 150% in the top layer. The difference expressed in millimetre between the lowest and highest rate amendment rate for the Stockosorb was broadly similar as in the top layer (19.0 vs. 16.4 mm). The justification of amending the lower half of the profile was less clear as the differences between the individual treatments tended to be lower.

Water retention in the lower layer 150 - 300 mm Vertical columns show confidence intervals at p = 0.95 65

water retention (mm) 40

peat 0 peat 5

peat 10 peat 15 peat 20 peat 30

zeolite 0 zeolite 5

sand100

zeolite 10 zeolite 15 zeolite 20 zeolite 30

compost 0 compost 5

compost 10 compost 15 compost 20 compost 30

stockosorb 0

terracottem 0

stockosorb 0.5 stockosorb 1.0 stockosorb 1.5

terracottem 0.5 terracottem 1.0 terracottem 1.5

stockosorb 0.25 stockosorb 0.75

terracottem 0.25 terracottem 0.75

Figure 2: The differences in a water retention among individual rootzones in the bottom layer

Photo 3: Experimental turfgrass plots at STRI showing a water deficit

The greatest decrease in soil moisture content was within one hour after saturation (Fig. 3). The peat and Stockosorb incorporated at the recommended rates had approximately the same water retention throughout the 48 hour drainage period after saturation of the top 150 mm of the profile. The total difference in moisture content between sand and peat treatments was 6.0% v/v after 48 hours.

Volumetric water content changes in the layer 0 - 60 mm

40,0 35,0 30,0 25,0 20,0 % v/v % 15,0 10,0 pure sand 5,0 peat 20% 0,0 compost 20% 0 1 2 4 8 24 48 zeolite 20% terracottem 1.0 RR Hours after saturation stockosorb 1.0 RR

Figure 3: The changes of volumetric water content measured by Theta probe in selected rootzones combinations

vwc (%) 8

peat10 peat20 peat30

sand100

zeolite10 zeolite20 zeolite30

compost10 compost20 compost30

Stockosorb 0.5 RR Stockosorb 1.0 RR Stockosorb 1.5 RR Stockosorb

Terracottem 0.5RR Terracottem Terracottem 1.0 RR 1.0 Terracottem RR 1.5 Terracottem

Figure 4: Volumetric water content after 48 hours in the top 0 - 60 mm

The differences in saturated hydraulic conductivity and water retention between the individual treatments are given in Table 2. There were large differences in water retention between the various amendment treatments and the amendment incorporation rates. In general the peat and the Stockosorb tended to retain the most water, in comparison to the other amendment materials. As expected water retention tended to increase as the rate of incorporation increased.

Treatment Saturated Water retention (mm) at 10 cm interval tensions from 10 cm to 60 cm hydraulic conductivity WR @ 10 WR @ 20 WR @ 30 WR @ 40 WR @ 50 WR @ 60 Ratio (mm hr-1) Peat 10% 520 27,6 27,1 18,8 10,7 8,4 7,9 20% 449 33,6 32,9 24,6 16,3 13,9 13,0 30% 291 41,9 40,7 34,3 25,3 22,4 21,1 Compost 10% 677 25,8 24,8 16,0 8,4 6,5 6,4 20% 664 28,7 27,5 20,2 11,1 8,8 8,7 30% 503 33,3 31,6 23,7 14,6 12,1 12,0 Stockosorb 0.5 RR 638 26,4 25,6 16,5 8,9 6,9 6,8 1.0 RR 615 31,1 29,4 20,7 11,7 9,4 9,2 1.5 RR 515 34,5 32,8 24,3 14,8 11,3 12,4 Terracottem 0.5 RR 698 23,9 18,6 14,1 7,3 5,2 4,8 1.0 RR 646 24,8 20,0 14,8 8,1 6,1 5,6 1.5 RR 695 26,4 20,4 15,7 9,1 6,9 6,5 Zeolite 10% 800 24,9 19,4 13,1 6,9 5,0 4,6 20% 808 26,4 19,9 13,0 7,6 6,0 5,8 30% 855 26,7 21,3 15,4 8,2 6,2 5,8 sand 100% 889 23,9 17,9 12,2 6,3 4,4 4,0

Table 2: Saturated hydraulic conductivity and water retention characteristics of individual mixes used for the experiment

Shear strength changes (transformed values, sand = 100%) F(4, 30)=22,996, p=,00000, Vertical columns show 0.95 confidental intervals 180 160

140

120

100 80 (%) values transformed

40 peat compost zeolite Terracottem Stockosorb

Figure 5: The differences in shear strength among used materials (sand = 100 %)

The shear strength of a rootzone is important particularly when rounded sands with a uniform grain size are used and if grass cover is damaged. This parameter essentially measures the mechanical strength of the growing medium. Figure 5 shows that organic amendments (peat and compost) led to significantly greater shear strength, whilst the use of superabsorbents led to decreased of the shear strength. This decrease in rootzone mechanical strength, when the superabsorbents were used, was due to the volume change of the polymer grains leading to a lower particle packing density and therefore less inter-particle friction.

Differences in hardness (transformed values, sand = 100%) F(4, 30)=15,574, p=,00000, columns show confidental intervals 0.95 140 130 120 110

100

hardness transf. (%) 70

40 peat compost zeolite Terracottem Stockosorb

Figure 6: The differences in hardness among the used materials (sand = 100 %)

Hardness of the rootzones influences the playability of the sport surfaces. The softest surfaces were produced when the Stockosorb was incorporated into the rootzone. This reduction in surface hardness can lead to problems with low ball bounce and a surface that is more prone to wear. The only inorganic amendment to increase surface hardness was Zeolite, probably as a result of the angular grain shape of the material leading to greater inter-particle friction. New techniques for turfgrass evaluation During my stay at STR I was able to assist the research and consultancy staff with their turfgrass trials, golf courses and football pitches assessment. I spent most of the time in the soil physics lab where next to my experiment I learned the key methods for assessing rootzone materials which included soil organic matter content by loss on ignition, particle size distribution, saturated hydraulic conductivity, and determination of water retention). I also learned techniques in turfgrass cultivar trials establishment, management and evaluation (e.g. height increase and measurement of turf colour). I also had the opportunity to take part in golf and bowling greens assessment (botanical composition, surface evenness, surface hardness, soil water content, soil sampling). During the objective assessment visits to football pitches I assisted in carrying out measurements of hardness, Poa annua content, water infiltration rate measurement, surface traction and rooting depth). Conclusions

Based on the results it can be stated that the most water retentive mixes were with superabsorbent Stockosorb and with sphagnum peat, followed by compost and zeolite and the least water holds Terracottem. Nevertheless for an objective assessment of plant available water amount the estimation of permanent wilting point will be necessary. Individual amendments influenced the properties of sand based mixes differently, but the lowest influence was measured at Terracottem. The recommended rate should be increased probably.

Outcomes of the Fellowship

It is anticipated that the results from this Stapledon Fellowship will be used to produce a paper for submission to a peer-reviewed journal. In addition to working on the specific project described here, I had the opportunity to observe and assist with a number of turfgrass measurement techniques during the Fellowship. This has greatly increased my knowledge and understanding of turfgrass science what I will use for improving of learning materials for students at Mendel University in Brno. I have acquired an understanding of how the turfgrass research and consultancy in UK function. I made contact with most research staff at STRI and with many at IBERS and I hope to cooperate together on some project in future. D. Thorogood guided me through the Aberystwyth University campus and through Gogerddan reaserch station. S. Hughes showed me round grass cultivar trials. M. Aberton talked to me about his research in red clover and generally about breeding programme at Gogerddan station, M. Humpreys made showed me with Festulolium characteristics and advantages for future use in agriculture, A. Lovatt familiarized me with system of grass and forage legumes genotypes collection, E. Jensen showed me Miscanthus experiments and T. Troop and J. Adams guided me through bioenergy trials. I was able to get know about grassland research of IBERS staff in some publications (e.g. Abberton et al., 2008). I was very happy I could meet Professor W. Adams (retired) who had worked on many projects whose aim was congruent with this one. Thanks to librarian of Thomas Parry library at Aberystwyth University, Stephen Smith, I was able learn more about the personality and work of Sir G. Stapledon who is inspiring man for grassland scientists and environmentalists (Waller, 1962). He was an honorary member of the Academy of Agriculture of Czechoslovakia. Thanks to Mr. S. Smith I was also able to get know more about British agriculture from statistics pages of Defra. I would like to use this information for writing a paper for some agricultural journal in the Czech Republic.

Acknowledgements

I would like to thank S.W. Baker for his help, provision of all requirements for my research project at STRI and for giving his time. I have to also thank staff of STRI namely Ch. Spring, A. Newell, F. Crossley, P. Reynard and M. Fergusson for their willingness and making me welcome. My special thank belongs to E. Yates and M. Baines from soil physics laboratory who taught me special techniques for rootzone testing. I am very indebted to D. Thorogood from IBERS who dedicated me 3 days during my stay in Aberystwyth and organized greatly my visit. I am very grateful to the Stapledon Memorial Trust for the opportunity that this fellowship offered me.

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Baker, S.W. (2006) Rootzones, Sands and Top Dressing Materials for Sports Turf. The Sports Turf Research Institute, Bingley, 112 pp.

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