Ronald Strahan, Koske, Thomas J., Stevens, Jr., J. Cheston | 6/27/2006 8:01:12 PM
More and more sports fields and golf greens are turning to high-sand-content fields. These are also called sand-based fields. The sand portion of the root zone mix is generally 75 percent to 100 percent true sand.
There may be zero percent to 5 percent (v/v) organic matter (OM) to start with until thatch, rhizomes and roots add to that percentage over time. Without much OM or clay, the cation exchange capacity (CEC) will be very low, and the soil nutrient cations are easily leached out. This is basically true for any very sandy native soil as well.
Many superintendents are now faced with this maintenance challenge of quick changes in nutrient and moisture status. They generally agree on the lessons learned about growing natural turf on sand-based root zones. Keep these principles in mind if considering or managing turfgrass on a sand-based soil or root zone.
Drainage in a sand-based field is usually good to excellent. It is downward percolation with some lateral internal movement of water. Lateral water movement in a sand profile is minimal, so an irrigation system must be well designed for uniform coverage, and water management then becomes a critical production practice. Sand fields will require less irrigation per watering but require watering more often because the sand holds less moisture down to 4 inches than a clayey or loamy soil. Most sand-based fields will not be built with a perched water table system that would hold some lower-profile water longer.
The amount of water held in the system will vary with the sand-size range and any amendments. Fine sands will hold more water than medium-coarse sand, but they percolate slower — perhaps 2 inches per hour or a lot less. You can gauge your irrigation by 1)moisture replacement based on evapotranspiration (ET) data, 2)soil moisture sensors and/or 3)visual evaluation plus experience history. With good sand, you can hardly overwater because of the high percolation, but that will waste water, stress the environment and require excess nutrient application. The moisture needs of sand-based turf is about the same as that in native soil; it's just that sand doesn't hold nearly as much available moisture as does a native loam or clay soil. Consequently, we irrigate sands much more frequently and with less irrigation output per watering event.
Pesticides can have a hotter reaction and greater phytotoxicity in sands. There is less clay, OM and CEC to tie up and slow down soil-applied chemicals. Pesticide labels usually specify more product be used on clay soils and less on sandy soils. Some labels not only mention soil clay content but also the percentage of organic matter present in the soil. A sand-based root zone would require even less than a sandy soil if that is the case, so be concerned about application rates and read the label more carefully when dealing with sand; it’s not the same as soil.
Fertility, other than soil pH, is best monitored by tissue testing. Soil tests are based on soils, not sand, thus soil test results are often much less useful with sand. With low CEC and high percolation, the nutrient status is very dynamic and should remind you of a hydroponic culture. Applied nutrients may be quickly available and quickly lost. Frequent light and complete feedings are a must. Light foliar feedings can work very well, and micronutrients are more of concern in sand than most soils.
Sand-based root zones have many good qualities that extend play on the turf, but they are not soils and act quite differently.