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nlunan@msn.com 203-537-0420 |
 "Broad Benefits of Biostimulants" |
How does an athletic field manager know when to use which tine? * Coring tines alleviate soil compaction most effectively. Pulling cores and dragging them back into the field produces highly productive results. Holes opened by hollow tines allow water and oxygen to reach turf roots. The turf usually responds immediately with growth. Hole spacing is an important factor with this type of aerification. With a 3/4-inch hollow tine, use 30 holes per square foot as your benchmark. More holes translates to more compaction relief, and over-aerifying a field is nearly impossible. Aerifying four to six times per year is not unreasonable by any means. Unfortunately, core aerification creates the most severe surface disruption of the different techniques. The procedure requires a field to be taken out of use for at least a couple of days. Crews need enough time to effectively aerify, drag in the cores, and irrigate the turf to ready the field for play. Also, soil moisture must be near field capacity before aerating, so the tines can effectively penetrate the soil to remove uniform cores. * Solid-tine aerification allows turf managers to aerate more frequently, since the procedure produces less surface disruption. Turf areas in soccer goal mouths, in front of the pitcher's mound on a baseball field, and between the hash marks on a football field can benefit greatly from weekly 1/4-inch solid-tine aeration. Solid tines larger than 1/4 inch in diameter open turf to allow water and air infiltration, but the process compresses displaced soil downward and to the sides. This actually increases soil compaction around newly created aerification holes. Repeated solid-tine aerification with larger-diameter tines can create a hardpan at the aerating depth. * Slicing tines can have the same effect as solid-tines on heavy-wear areas. They can also stimulate turf growth by cutting turf rhizomes and stolons. * Deep solid-tine aeration can alleviate hardpan with little surface disruption by opening the soil profile to depths ranging from four to 18 inches. Deep hollow-tine aeration is generally not recommended on native-soil athletic fields. Pulling cores from deeper than four inches usually brings poorer-quality soil to the surface, and defeats the purpose of the original soil modification effort. No matter which aerification technique you choose, be sure to vary the depths of the tines over the growing season to avoid forming a hardpan layer. Topdressing: A common fallacy of native-soil athletic field management is that topdressing with sand will improve soil structure and drainage. Most soil fields have high concentrations of silt and clay. Adding sand to this mix will only decrease a field's percolation and make it harder. Consider the ingredients used in concrete: sand, silt, and clay mixed with water! Over time (10 to 30 years), topdressing will gradually build up sand concentration in the soil and improve the field in the long run. However, in the short term, adding sand actually makes a native-soil field worse. The sand fraction of the soil must reach 60 to 70 percent in the top three to four inches before topdressing with sand will help drainage and infiltration characteristics. There is a better way to modify a problem native-soil field with sand. Harvest the cores after a hollow-tine aerification. Then topdress with enough sand to completely fill the holes. This method allows water to better infiltrate the aeration holes. Over time, much more of the problem native soil can be replaced with sand, as opposed to simply being mixed with the sand. This method is not without its drawbacks. Depending on the size of the field and the diameter and number of holes, up to 60 tons of sand could be needed to completely fill the holes. Topdressing this much sand at one time can be prohibitive, and it can produce a sand layer on top of the soil if the sand is not properly dragged into the holes. A sand layer on top of native soil leaves turf susceptible to divoting and shearing-type injuries, because the sand layer can slide off the top of the soil layer under athletes' cleats. Diatomaceous earth or calcined clay products are often a good alternative. These materials increase pore space within the soil profile if worked into the soil during aerification. Of course, these options are considerably more expensive than topdressing with sand. Aeration cores make the best topdressing for native-soil fields. When you drag cores back into the field, most of the soil will fall back into the holes, but some of it will topdress the turf in the process. Take a physical soil test of each of your fields. This will reveal the respective fractions of sand, silt, clay, and loam. If you're going to initiate a regular, heavy topdressing program, your mix should closely approximate the test results. Even with a proper crown, good aerification and topdressing strategies, and properly constructed drainage, there are times when a field is simply too wet to allow play after rain. When play threatens to severely damage and compact the soil, field managers must work with the coaches to relocate field activities. Wisely using a field every day is as important to the life expectancy of a native-soil field as construction considerations. Dan Bergstrom is athletic field manager for the University of Kentucky in Lexington. |
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