Soils

Understanding soils

Sports turf managers are charged with providing cost effective, safe playing surfaces for athletes. The challenge is to create a uniformly dense turf cover that provides sure footing and one that is able to tolerate and recover from the extreme wear and tear to which high-use fields are subjected to.

Although newer, properly designed fields may be constructed to handle more intense use, many school and community sports fields were built on existing “native soils” that are often less than ideal.  These soils may or may not have the best properties for sports field use but in many cases can perform well if managed properly.

Soils are made of varying amounts of:

  • Mineral solids - grouped into 3 main categories based on particle size; sand, silt, clay
  • Organic matter - material that originates from living organisms
  • Water - essential for soil and plant life and enables plants to take up nutrients
  • Air – that provides the oxygen required by plant roots and soil organisms to grow and function
  • Micro-organisms – including bacteria, fungi, actinomycetes, nematodes, etc.
  • Macro-organisms – including earthworms, insects and millipedes

To say "the life of the soil" is important is an understatement. The life of the soil (micro and macro-organisms) helps maintain soil structure, suppress some plant pests, breakdown organic matter, mineralize and recycle nutrients, fix nitrogen and detoxify pollutants. Turfgrass management practices that support the “life of the soil” include: using organic amendments, maintaining adequate water and nutrient levels, improving soil porosity and limiting the use of pesticides.   

Importance of soil physical properties

The amount of water, air and nutrients available for plant growth is affected by the soil physical properties and turf management practices that include watering, mowing, and aerifying and how much the fields are used.  Determining the physical properties of your soils will ultimately help you determine how to manage them effectively.

Soil texture is based on the relative proportion of sand, silt and clay the soil contains and is used to name the soil, for example a sandy loam soil.   

Coarse-textured soils (sands, loamy sands, sandy loams) have a large particle size and do not have great water and nutrient holding capacity. They tend to be well drained, dry out faster, and are less likely to compact.

Fine-textured soils (clays, sandy clays, silty clays) have a small particle size. They can hold water and nutrients, take time to dry out, can be easily compacted when wet and often are associated with poor drainage that limits the use of the fields during wet weather.

Soil texture will influence watering and fertilizing management practices on sports fields.  

General soil physical and chemical properties of different soil textures

Soil texture Drainage Susceptibility to compaction Water & nutrient-holding capacity
sand excellent little to none limited
loamy sand excellent limited limited
sandy loam good limited to moderate moderate
loam good to fair moderate moderated – substantial
silt loam fair to poor substantial substantial
clay loam fair to poor substantial substantial
clay poor substantial substantial

Determine the soil type

Knowing the soil type is important and can differ from area to area and from field to field. The name of the soil is also necessary when submitting a soil sample for nutrient analysis.

If you are not familiar with the soils you have, you can have a customized Soil Resource Report generated for a particular parcel of land by going to the NRCS (Natural Resources Conservation Service) Web Soil Survey website. 

Or you can use the SoilWeb for the iPhone app from the California Soil Resource Lab. (Also available for Android.) This application retrieves graphical summaries of soil types associated with the phone's current geographic location.  Sketches of soil profiles are linked to their official soil series description.

If soils were brought onto the site, the above methods for determining soil type may not be very useful. Some soil testing laboratories (including the Cornell Soil Health Testing Lab) can determine soil texture. Also, you can get a good idea of the soil texture by following the texture by feel method. View University of California video: Soil texture by feel.

Soil structure

Soil structure refers to the arrangement or grouping of soil particles into granules or blocks of soils in various sizes and shapes. A well aggregated soil is good for plant growth because the wider range of pores provides better drainage, aeration and water storage and places for roots to grow. Soil aggregates (crumbs, or clumps) are formed when soil minerals and organic matter are bound together with the help of organic molecules, plant roots, fungi and clays.

Both air and water occupy the pores spaces created within and between soil aggregates. Air can be found in the larger pores (macropores) and water is held in the smaller pores (micropores).

Soil structure can be destroyed by over use and traffic and can be improved over time by incorporating amendments through topdressing.  

Drainage management

Soils for sports turf must have good footing and traction for athlete safety and performance.

Soils that are easily compacted, have a low amount of organic matter, have poor nutrient and water holding capacity and poor drainage are not suitable for sports turf.

Organic soil amendments (i.e. compost, peats) function by enhancing soil structure (in non-sandy soils) and aeration as well as contributing to improved nutrient and water retention. Soil resiliency can also be increased with organic amendments. Learn more about composts and compost testing.

Inorganic amendments (i.e. sand, calcined clay, diatomaceous earth) can be used to improve drainage and aeration along with water and nutrient holding capacity.

Long term improvement in soil properties can be achieved by topdressing. Topdressing with ¼ - ½” of screened high quality compost or lesser amounts of sand after aggressively core aerating the soil will begin to improve the soil’s drainage and aeration properties. Depending on your goals this may need to be repeated a couple of times per year.

Soil texture Management strategies

Coarse-textured soils:

  • Sands
  • Loamy sands
  • Sandy loams
  • Add organic amendments to increase organic matter content, improve water and nutrient holding capacity and support microbial activity.
  • Fertilize carefully: apply smaller amounts of fertilizer more often or use organic or slow release fertilizers. Do not apply if heavy rain is expected.

Fine-textured soils:

  • Clays
  • Sandy clays
  • Silty clays
  • Add organic amendments or sand to improve aeration and drainage.  Using organic amendments can also support and enhance microbial activity.
  • Do not use when wet.

Compaction

Compaction breaks down soil structure and reduces the amount of pores space for air exchange, which is necessary for root growth and microbial activity. It also reduces the amount and rate that water can infiltrate into the soil and percolate down through the soil profile.

Compaction is more likely to occur on fine-textured soils and less likely a problem on fields with coarse textured soils.

Management options include various cultivation practices such as coring, slicing, spiking, grooving, water and air injection, drilling and solid tine cultivation. These operations still must be done at the correct time, at the proper depth when soil conditions are not wet and are required more often on high use fields.

Drainage

Drainage is the removal of excess water from the soil surface and/or soil profile either by gravity or artificial means. Some fields may have adequate drainage because the field was constructed properly. However, poor drainage is one of the most common problems of high use sports fields.

Improving Surface Drainage

When water remains on the field surface and does not drain many problems occur including slippery and unsafe conditions. Games are cancelled and maintenance practices are delayed.

Wet soils take a longer time to warm up in the spring and seed germination can be delayed.     

The raised portion of a sports field that provides a slope to promote runoff of surface water is called the field “crown”. Crowns are the most effective way to remove surface water because they move water the shortest distance possible.

Football fields should have at least a 1-2% slope. The highest point is usually about 10-18” above the lowest point on the field. Soccer fields made of native soil typically are built with a minimum of 1½ % slope and should never be flat. If the fields have underground drainage the slope should be at least 1%.

Crowned fields are not suitable for multiple sports because they cause difficulty in ball control sports like soccer and field hockey.

The water that is directed to the sidelines will need to be collected by interceptor drains and move away from the field.

Improving Sub-surface Drainage

Sub-surface drainage can be effective at removing excess water from the rootzone during high rainfall events and for reducing the water table. These systems assist in moving water out of the soil profile by providing a pathway for “excessive” or “drainable” water to leave the soil. They work the best when good surface and internal drainage are in place.

There are a few commonly used systems to help improve sub-surface drainage including pipe drains, interceptor drains (also known as French drains), trackside drains, strip drains and sand-slit drains. A thorough discussion of each of these methods can be found in fact sheets from the Sports Turf Managers Association.

Use the information to assess your drainage problem and select the appropriate approach for correction.

Building a Sand-Cap

Michigan State University (MSU) offers an alternative to complete renovation of native soil fields with high silt and clay content and drainage problems. The Sand-Capped System uses the installation of a subsurface drain tile system followed up by sand topdressing to build up the soil profile over time.  See Sand Cap Build-Up Systems for Michigan High School Fields.

There are four steps for building a sand-capped system. Based on 2008 cost figures the system can be built for $58,200 - $103, 800 (this includes an irrigation system installation ($15,000), 6-20 foot drain tile spacing ($14,200 and $60,000, respectively), and a 2-inch sand layer depth ($28,800). It is believed that this would provide a cost effective solution to improve field playability that does not interrupt field use for an extended period of time.

Steps include:

  • Cutting drain lines in the existing field running length wise
  • Putting drain tile in the lines
  • Back filling with peas stone and then sand or coarse sand alone

MSU suggests installing an irrigation system (before the drain tile installation) if one is not present because turf grown on a sand-based system will need regular irrigation. Be sure to correct any low or wet spots in the existing site and repair any drainage line damage found.

Once installed, an aggressive sand-based topdressing program must be initiated and maintained using a well-graded sand-based material ~90% sand: 10% silt/clay.

Soil testing: Essential management tool

Why soil test?

Soil tests evaluate the nutrient supplying power of the soil and report phosphorus (P), potassium (K), calcium (Ca), Magnesium (Mg), minor nutrients, percent organic matter and the soluble salt level and soil pH. Soil test results provide the foundation information for building a sports turf fertilizer program and can also be used to diagnose problems related to nutrients and soil pH. 

With soil test results you can:

  • Adjust soil pH
  • Determine amount of required fertilizer
  • Avoid over/under fertilization
  • Utilize an environmental protection tool

Select a lab to work with

Cornell’s Turf Team provides the fertilizer recommendations for soils tested at Agro-One

Soil test results may from lab to lab vary because several methods can be used to extract the nutrients from the soil sample when estimating the nutrient supplying power. Although the levels may be different, the interpretation (very low, low, medium, high) should be fairly consistent between reputable labs.

Select a lab service that uses soil test calibration data from New York State soils to interpret the results.

Cornell University works with Agro-One, which is a department within Dairy One, to perform the analytical work while the recommendations are provided by Cornell University from research based information conducted by Cornell’s turf team. 

Recommended soil test packages

For mineral soils (non-sandy) request the 855 Standard soil test package which will provide soil pH, lime requirement, percent organic matter, and phosphorus, potassium, calcium, magnesium aluminum, iron, zinc and manganese levels and recommendations.

For sand-based fields request the following to be tested: soil pH, phosphorus, organic matter and cation exchange capacity (CEC). The standard tests are not as useful when testing sand-based soils. The CEC measures the capacity to hold nutrients potentially available for plant uptake and provides more useful information.

When do I begin soil testing?

Soils can be sampled any time the ground is not frozen. Allow time to take and submit samples, receive the results and order the fertilizer. Some managers like to sample and have soils tested in the fall or early spring to plan for the next year’s fertilization program and budget.

A soil test should be conducted when establishing a new site and every 2-3 years on established sites. To obtain meaningful and useful test results, sample soil correctly, at the same time each year and maintain fertilizer records.

How and where do I soil test?

Take a good soil representative sample

Always follow the soil sampling instructions provided by the soil testing lab you use.   

You can use a soil probe or towel to take a sample

Sources of Soil Test Probes:

Be sure to follow these soil sampling steps:

  1. Always take samples at a consistent depth, preferably 4”.
  2. Take about 10-20 cores from a uniform area, similarly managed, using a zig zag pattern to ensure that overall field conditions and variability are taken into account.
  3. Remove live plant material or thatch
  4. Mix the soil in a clean plastic container to provide about 1 cup of a composite sample
  5. Air dry the sample before sending it to the lab if possible
  6. Complete and include the submission Form T (for commercial turf samples). 

When you complete the form be sure to include:

  • crop code (ATF for athletic fields submitted to the Agro One lab)
  • soil name (Required for Agro-One nutrient guidelines in NYS. See links below to find your soil name.)
  • soil texture and drainage
  • tests requested

View sample submission form.

Soil test name and description can be found using several resources:

Keep records on file

Soil test results should always be kept on file and used to adjust fertilizer programs over time.