Proper sports field construction usually involves an expensive subsurface drainage system, specialized root zone modification, and subtle surface drainage contours. It is a critical aspect, since improper construction due to cost-cutting results in the higher long-term maintenance costs, problems in maintaining a quality playing surface, frequent loss of turf, and costly reconstruction (Beard, 1973 and 1982). The steps in construction are:

1. Survey and stake.
2. Construct sub grade.
3. Install a subsurface drainage system.
4. Modify root zone:
a construct drainage layer.
b construct coarse sand zone.
c mix and install specified root zone.
5. Install irrigation system.
6. Finish surface contours.
7. Plant
a soil pH adjustment, if needed.
b fertilization based on soil tests.
c plant.
d post-plant care.

By following the suggested specifications of the Texas-USGA Method, tens of thousands of greens have been constructed during the past 30 years and, more recently, many sports fields have been constructed and successfully used throughout the world.

Sub grade.

Contour the sub grade so it conforms to the proposed finished grade, with a tolerance of 25 mm. The sub grade should be 450 mm below the planned finished grade and should be firmed to prevent settling. Care should be taken to ensure that the final sub grade base contours, within the overall slope, drain: gravitational water to the nearest drain line.

Subsurface Drainage System.

A herringbone or gridiron design is utilized, with 100 mm diameter drain lines spaced at 4.2 to 6 m intervals at a minimum grade are with 0.5 percent. The drain line trenches should be cut into the sub grade at as shallow a depth as possible. A 38 to 50 mm depth of 6 to 10 mm diameter crushed stone or gravel is placed in the bottom of the trenches and drainlines laid. Than additional stone or gravel is placed around and over the drain lines to fill the trenches.

Drainage Layer.

Angular, hard, noncalcarious, washed, screened river run gravel or crushed stone involves 6 to 10 mm diameter should be selected for covering the sub grade to a minimum settled depth of 100 mm. The proper sized crushed stone or gravel must be obtained to prevent migration of the same into the gravel or stone bed and thereby preserve the integrity of two distinct layers: the upper high-sand. mix over gravel or crushed stone.

This drainage layer functions in the rapid lateral movement: gravitational water to the drain lines. Also, the porous crushed stone or gravel base prevents the upward capillary rise of salts from the soil base into the root zone. During installation, the crushed stone or gravel is typically dumped from the delivery trucks on the perimeter and then distributed over the construction site by a small, tracked crawler tractor, being careful to avoid driving over and crushing the drain lines.

Course Sand Zone.

A 50 mm the layer of washed, screened, hard, angular course sand holds 1 to 2 mm diameter is carefully spread over the drainage layer. The specific size of the same particles must be within 5 to 7 diameters of the underlying crushed stone or gravel.

Thus, if 6 mm stone or gravel user used, the particle size of the course sand zone should be not less than 1 mm diameter. This course sand design has to be functions:
1. To prevent infiltration of the high sand root zone makes into the spaces between the drainage layer particles.
2. To create a perched hydration zone of plant available water immediately above the drainage layer in be lower portion of the high sand root zone mix. The distinct interface between the course sand zone and be up a 300 mm all of settled high sand root zone mix disrupts the continuity of surface interfaces among the particles and the downward movement of water. When the perched hydration zone above the interface approaches water saturation, the force of gravity overcomes the interface perched effect and the excess water is released downward.

Installation of the course sand zone is best accomplished manually, taking care to Not mix the sand with or into the drainage bed. The course sand is dumped from the delivery trucks on the outside perimeter, and is typically moved across the crushed stone or gravel by wheelbarrows over a path of plywood boards.

This thin course sand layer presents some difficulties in installation. However, this intermediate design is critical to the overall concept and is a modest long-term investment compared to turf failure and rebuilding costs if improperly constructed.

Substitution of a non-biodegradable screen-like material for the course sand intermediate zone has been proprietors. Problems have been observed with these geofabrics which tend to become clogged to the extent that they are impermeable to water and may cease to drain. However, a more open, nonfilter mesh or netting may be used between the intermediate course sand zone and the drainage Layout when using gravel to provide a stabilizing effect during construction. This netting should not be necessary when using angular crushed stone to to the stability of this material.

Ringing the Perimeter.

Polyethylene sheeting should be permanently inserted as a vertical barrier between the outer native soil and be read zone mix. This barrier prevents lateral water transfer into the adjacent dry soil, which would course perimeter turf warter stress.

When the sheeting is extended 100 to 150 mm above the surface during construction, it will also function in preventing erosion of unwanted soil onto the construction area.

Root Zone Mix Installation.

Quality-control is the key to successful execution of root zone modification All root zone mixing should be completed off the construction site, termed off-site mixing. Although it sounds good, in practice the procedure: in-place rotary tilling of the organic and/or components into the high sand component has not been successful.

Every truck load of each component in the soil mix, as well as the gravel and course sand, should be checked at delivery to ensure that the specifications are met.

Off-site mixing includes soil shredding, screening to remove any objectionable stones, and addition of the specified proportions of each mix component. Because of the narrow range in acceptable limits of the physical properties, it is very important that the laboratory recommendations be explicitly followed in mixing the components of the root zone mix. Upon confirmation that the root zonemix has met the specifications, it is transported to the construction site and dumped around the perimeter onto the course sand zone.

A small, crawler tracked tractor with blade then pushes the mix over the area being careful to avoid crushing the drain lines. Be sure the unit is operated with its weight all root zone mix. This reduces the chance of disturbing the lower construction profile.

Caution.

Use of wheeled tractors courses rutting and they are more likely to crush the drain lines than are tracked vehicles. Grade stakes placed in a grid pattern at 3 to 4.5m intervals will aid in constructing the final contours to the specified root zone depth. Success has been achieved by carefully selecting the components of the root zone n-mix and by careful adherence to the construction guidelines.

Texas-USGA Root Zone Mix Specifications.

The greatest problem encountered in maintaining turfgrasses on sports fields is soil compaction. This pressing together of the soil particles into a more dense mass results in impaired drainage of excess water and a loss of proper Aeration needed to provide oxygen for healthy root growth. As a consequence, there is a general decline in turfgrass health, vigour, and recuperative ability following turf injury from wear stresses.

Soil compaction and the resultant negative effects can be minimized by selection of a high sand root zone of the proper particle size distribution and associative key physical and chemical characteristics. The result is minimum proneness to compaction, adequate drainage of excess gravitational water, and proper aeration to provide needed oxygen for root growth and related to soil biological activity.

However, such wise sand root zone's are very droughty due to pour water retention capacity unless a perched hydration zone, such as achieved through the Texas-USGA method, is utilized in the construction specifications. In addition, high sand root zone's tend to have a low cation exchange capacity, thus, the leaching of the the essential plant nutrients is a greater concern, particularly during the initial years following construction. This potential problem can be minimized through the use of slow release nutrient carriers and/or the timely use of foliar feeding techniques.

Composition of the 300 mm settled depth of root zone mix should be selected based on specific physical tests conducted in a reputable physical soil test laboratory. The test report specifies the particular materials and the percentages in which they are to be mixed. They decide characteristics for a Texas-USGA method root zonemix are given in the following paragraphs.

Component Descriptions of Root Zone Mix.

It is important that the three components selected for the root zonemix be free of toxic levels of materials such as heavy metals, persistent crop herbicides, and industrial organic chemicals. Minimal amounts of soluble salts, Boron, and sodium are preferred.

Angular, hard, washed, screened silica sand is strongly suggested. Avoid high pH calcareous sands. The preferred sand component particle size is: 100 percent below 1 mm, 65 percent below are 0.5 mm, 25 percent below 0.25 mm, and five percent below 0.05 mm. Note: the mesh sieved size refers to the U.S. Standard of the United States Department of Agriculture (USDA).

It is suggested that the organic matter source selected be well decomposed and have no more than 15 percent ash or mineral content, preferably less than 10 percent mineral content. Examples include peat humus and ree-sedge peat. The organic material should be shredded to insure mixing uniformity, but not to the degree that the material is pulverized thereby causing reduced soil water infiltration.

Soil Component.

A sand, loamt sand topsoil is suggested. The source should be shredded to insure mixing uniformity and should be screened to remove stone and other debris.

Composite Root Zone Mix.

Particle Size Distribution.

It is suggested that the root zonemix obtained less than 25 percent particles smaller than 0.25 mm, and contain less than five percent silt and three percent clay. The suggested specifications for the particle size distribution of the root zonemix are shown.

Mix Water Infiltration Rate.

The preferred Water Infiltration rate for a laboratory compacted root zone mix using the range of 150 to 300 mm per hour. The right in the laboratory tests should not exceed 600 mm per hour.

The upper limit in the Water Infiltration rate is designed high enough to account for the normal on site reduction in Infiltration rate that occurs during the first three to four years due to increases in roots and organic material.

Mix Aeration Porosity.

An acceptable total pore space volume is between 40 and 54 percent. The preferred distribution would be 22 percent capillary and 25 percent non-capillary pore space. Noncapillary pore space should be not less than 15 percent. The measurements are my aid on a root zone mix that has been allowed to percolate water for 8 hours and then is drained at a tension of 400 mm of water.

Mix Water Retention Capacity.

An acceptable laboratory established 400 mm water retention capacity would be between 12 and 25 percent by weight on a 105 to 111C oven dry soil basis.

The available water in the sod is estimated to be that held at a tension of 400 mm of water, which is the approximate distance from resurface to the drain line.

The preferred Water Retention capacity is 18 percent, or 1.5 mm of water held per 10 mm of soil.

Mix Bulk Density.

The preferred root zonemix should have a bulk density of 1.4 grams per cc; with a minimum acceptable bulk density of 1.2 and a maximum of 1.6 g per cc.

pH

The acceptable pH range is 5.5 to 8.0, and the preferred pH range 6.0 to 6.5.

Soil Salinity / Electrical Conductivity.

The acceptable range is less than 4 millimhos per cm, with the preferred range being between zero and one.

Soil Sodium Level.

The acceptable range is an exchangeable sodium percentage (ESP) of less than 15, with the preferred being a minimal sodium level.

Root Zone Mix Analysis.

The starting point in selection of a root zone mix involves obtaining detailed physical and chemical descriptions of the components being considered for a root zone mix and how they respond when n-mixed in various combinations. One or more representative samples of each sand, organic matter, and sandy sore component under consideration for use should be submitted to a reputable physical soil test laboratory. Only a few physical soil testing laboratory's are equipped to conduct these specific Texas-USGA but method tests.  

The primary laboratory physical determinations made of the particle size distribution, bulk density, and the mineral composition. The next laboratory step is to combine serious proportions of the sand, organic matter, and sandy soil, based on physical determinations. These trial mixes are compacted and then evaluated for water infiltration rate, moisture retention, bulk density, and pore space. Mixes are made and tested until one is found that conforms to the standards. Recommendations as to the relative volume of each component to be used are then given.

The crushed stone or gravel for the drainage layer and the coarse intermediate sand also should be tested for particle size diameter to assure that the root zone mix does not washed down and block the drains.

In addition to recommendations concerning the appropriate sand, organic matter, and soil materials and their mix proportions, a description of the chemical properties of each material is needed. Included are the pH, total salts, and levels of P and K.

Submitting Soil Materials for Testing.

A laboratory physical analysis requires a minimum of 8 litres of sand, and 4 litres each of organic matter, soil, intermediate coarse sand and crushed stone or gravel. If there is a choice of sands, organic materials, and sandy soil, send samples of each along with a note indicating a preference based on cost, accessibility, and quantity available. These laboratory will attempt to use the preferred, most cost effective materials in the recommended root zone mix.

Representative samples of the materials must be collected. If the materials are stocked, make sure to compensite several samples dug from within the side or top of the stockpile. Materials near the edge or on a sloping surface may not be representative. Make sure that a prospective vendor will have sufficient stocks of uniform materials over a long period so that if there is a delay of a few months, the materials available at the time of construction will be the same as the original samples tested. All samples should be packaged separately and securely. Strong plastic bags inside cardboard cartons or metal cans are most satisfactory. Use plastic labels inside the package and also to mark the outside of package.