SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/369217
www.stma.org September 2014 | SportsTurf 9 will the development of compacted layers within the soil profile. Any reduction in rooting depth will decrease the water and nutri- ent uptake of the plants, which ultimately has a negative impact on plant growth. Given the intense use of most athletic fields, this is obviously a situation we want to avoid. There has been a significant amount work done to determine the ideal range of soil textures for use on athletic fields with recom- mendations often varying slightly depending on geographic location and intended use. I'm not going to get into that here. Chances are that you do not have the luxury of choosing the soil texture of the fields you are managing unless you are lucky enough to be involved in a new construction project or a significant renovation. That being said, I still feel it is important that you have a good understanding of where your fields stand with regard to soil texture. In most cases it will not be necessary to submit samples for textural analysis. However, it would be good to pull some soil cores to depth of 10 to 12 inches from a few random locations in each field to get a better idea of what you are dealing with, particularly if your field was constructed using native materials. Pay particular attention to the consistency of soil texture from top to bottom of each core and from one location to the next. While you will expect some variability from one loca- tion to the next, particularly with a native soil field, you want to see a consistent soil texture throughout the depth of the soil cores (photo 1.). Note any changes in soil texture as they can lead to problems with water infiltration and root growth. Abrupt changes in soil texture in the soil profile, often referred to as layering, can impede water movement through the profile leading to the surface staying wet longer after rainfall and irrigation events (photo 2). If the soil surface is at or near saturation while being used, the field will wear out more quickly. To make matters worse, the water in a soil at or near saturation acts as a lubricant for the soil particles allowing them to slip past each other more easily lead- ing to increased compaction (bulk density) of the soil. As bulk density in the soil increases it becomes more difficult for plant roots to pen- etrate the soil leading to a reduction in water and nutrient uptake. In extreme cases, soil com- paction can result in surface hardness (Gmax) levels that increase the risk of impact injuries to athletes using the field. For example, the Clegg Impact Tester is used to monitor surface hard- ness on all NFL fields. The NFL has established a maximum threshold value of 100 Gmax for all natural and synthetic fields. Given the intense use that most athletic fields receive, effective management of soil compaction on athletic fields is just as impor- tant as a well-developed fertility program. Once you have a good understanding of the soil conditions you are dealing with on your fields you can begin to develop an aerification program to address any problems that exist. In general, aerification practices should be conducted on actively growing stands of turfgrass. For cool-season areas you can begin a heavy core aerification program in the spring before the first fertilization followed by light coring/pencil tining during the summer months when the grasses are under more stress and more aggressive aerifica- tion again in the fall. Aerification of warm-season grasses should not begin until late spring or early summer once the grasses are growing vigorously. In both cases, high traffic areas should be cultivated 6-8 times a year at a minimum to maximize plant health. Left: (Photo 1) A soil core removed from an athletic field built with a sand-based rootzone. Note the consistent texture throughout the depth of the core, lack of any compacted layers and minimal organic matter accumulation at the surface. Right: (Photo 2) A soil core removed from an athletic field depicting the layering of different soil types. At the bot- tom of the core there is a fine-textured soil that is high in clay, above that there is a 4-inch layer of sand that has been topped with an additional 3 inches of fine-textured topsoil.