Playing the infield
Caring for turf can be a challenge even under normal conditions. Factor in heavy use and time constraints, and it becomes even more challenging. Add to that the requirement for turf to look its best at all times, and you've just entered the world of sports field management. Sports fields are some of the most challenging areas in turfgrass management. How do you balance the special needs of sports field turf? The key is to get in tune with turf. Start by reading below to get an idea of how to approach the task of maintaining established infields. Keep in mind that new baseball and softball infields require different care and management than fields that have been established for a season or more.
Your first step in determining how to care for infields is to consider the demands that will be put on the field. What will be the level of play? Will the field host one to two games a week, or will 20 games a week be played on it? Is the field used for practices as well as for games? Other critical pieces of initial information include your budget for turf care, the manpower available and access to equipment.
Consider this: How many players play on the turf of a baseball field? The answer: only three — the three outfielders. The remaining six play mainly on the skinned area of the infield. The infield gets wear only in front of the pitcher's mound and around the first base cutout. And the cutout around the bases can be enlarged so the area of primary stress will be only in front of the pitcher's mound.
With this in mind, your turf management program can be more focused. Even if the budget for materials is low, correct cultural practices can go a long way to help you offer a quality playing surface.
Turf species is also very important in the development of a quality program. What species of turf is on your field? In recent years, the use of bermudagrass on athletic fields in the Transition Zone has increased greatly. The care of bermudagrass in a northern climate is different than in a more southern climate. The mixture of bluegrass and ryegrass is still the main mixture for northern fields, while bermudagrass is the flagship of the South. However, the use of tall fescue is increasing, especially on the sidelines, where most of the stress and wear around the infield occurs.
In the South, if shade from stands or buildings causes a problem in keeping bermudagrass healthy, seashore paspalum may prove to be a suitable replacement. It is similar to bermudagrass in many ways but is much more shade tolerant. Each of these species requires slightly different management practices.
The majority of sports fields are composed of native soils, non-modified. It is important to have a texture analysis done on your soil. Having this test performed will provide you with the percentage of sand, silt and clay. Knowing about the texture is important because it can provide information about how the field can handle play and determine what agronomic practices will be necessary for you to keep the field playable.
Each of the different textural components is separated from the other two by its physical size: sand is larger than silt, which is larger than clay. The textural components vary in the pore size that forms between the soil particles. The larger pores that are formed between particles of sand allow easy infiltration, that is, they allow water to easily enter the soil; however, the overall volume of water that sandy soils can hold is less than clayey soil can hold. In addition, the ability of the soil to hold nutrients, or the cation exchange capacity (CEC), is greater in clay-based soils than in sandy soils.
The main problem with clay-based soil is compaction. When soil becomes compacted, the soil structure is physically destroyed. This ends up eliminating the pore space between the particles. This not only prevents the infiltration of water, but it also limits the amount of oxygen contained in the soil.
A proper aeration program is one of the most important cultural practices that can be performed on the field. Aeration is important on all soils, but it is critical on soils that have a heavier clay texture. The amount of oxygen and water that can infiltrate into the soil is critical for root development and survival.
The relationship between water and oxygen is crucial for the life of the plant. Nutrients required for plant health and growth are dissolved in the soil solution and are absorbed through root hairs. The absorption process requires the plant to burn energy to take up the water and nutrients. For this process to occur, the root needs to absorb oxygen from the soil. So, if either water or oxygen is out of balance, nutrient uptake is limited.
When soil is compacted, the texture of the soil does not change, but the structure does. In the majority of soils, when compaction occurs, aeration is the only practice to correct it. Aerating equipment ranges in price and effectiveness. Some equipment simply pokes holes in the soil; more expensive equipment will pull a soil core; others pull a core and shatter the soil to a depth of 12 inches or more. Agronomically, it's difficult to aerate too much; but realistically, your aeration will revolve around use of the playing surface because aeration will disrupt use of the field.
Cool-season turf is best aerated in the spring or fall, and warm-season turf should be aerated in the summer. A general rule of thumb is to have 30 to 45 good growing days following cultural practices such as aeration. Heavier clay soils can be modified by topdressing with a sand mixture following aeration. As this is a specialized operation, it is recommended that you contact someone with experience in your area prior to beginning a soil modification process.
Proper fertilization is the backbone of any good maintenance program. A soil test is the best initial step to determine needs. This will tell you what nutrients you currently have in the soil. Standard soil tests do not include testing for nitrogen. A proper nitrogen program should be based on the requirements of turf on your field, your location, the soil texture and, lastly, your budget. Standard soil tests will provide information on phosphorus, potassium and soil pH. Other nutrients can be included in the test if requested. Most native soils contain sufficient micronutrients to grow healthy turf and supplemental applications are not needed.
The exception to this would be iron. Iron is a useful nutrient to the groundskeeper as it enhances the green color of turf without encouraging topgrowth. This is especially useful in the spring when baseball and softball are being played. Refrain from making heavy applications of quick-release nitrogen in the spring. This can cause the plant to initiate a flush of leaf tissue, using energy needed for root development.
After taking a soil test, you will know if any particular nutrient is deficient. Correcting any deficiency should be a part of your regular nutrient program.
Tissue testing can also be helpful because the soil may contain a nutrient, but the tissue test will show if the plant is actually capable of absorbing it. Tissue testing done at different times of the year under different conditions will show how the plant is responding to both environmental conditions and cultural practices.
Keeping records of both the soil and tissue testing will show a pattern in the life of the turf. The actual growth of turf is the best indicator of the need for nutrients, such as nitrogen. Following the standard growth cycle of the turf species, monitoring such things as clippings can provide information on how the turf is responding. Understand what your plant is telling you. Again, turf grown on highly modified soils will have to be treated differently than most native soils. Sands do not have high CECs. Nutrients that are not cations, such as nitrogen, will leach quite readily, so you should monitor them for deficiencies.
Over the past several years, the market place has seen a rise in specialty products, such as biostimulants. Recent research has shown that the addition of biostimulants during root development will enhance fertilizer activity. Both research and end-user testimonials have shown that most of these products can provide beneficial results. The use of plant hormones and humic-based products can help plant roots and provide stress prevention.
Stress in turf is caused by a variety of environmental factors including field play. Regardless of cause, stress weakens the turfgrass plant. Once stressed, the plant becomes susceptible to other problems. Disease, reduction of photosynthesis or a decline in the production of hormones such as cytokinins and auxins are more likely in stressed plants. University research has shown that when a grass plant is stressed, normal metabolism is disrupted and oxygen is left in an unstable state. Unstable oxygen is called reactive oxygen or free radical. In this state, the oxygen can be very damaging to plant cellular tissue. Chlorophyll and other parts of the chloroplast are susceptible to damage from free radicals.
Plants possess chemicals known as antioxidants, which combat free radicals. When the plant is under stress, the volume of free radicals is greater than the volume of antioxidants naturally produced by the plant. An overabundance of free radicals increases stress and reduces the photosynthetic potential for recovery. Applications of biostimulants, which supplement plant hormones, have been shown to enhance the presence of various antioxidants in the leaves, reducing stress and promoting faster recovery from injury. Applying this type of biostimulant product to sports fields several weeks prior to the beginning of play and following up with regular applications during the season can enhance the presence of antioxidants for stress reduction and recovery.
If you have a fall fertility program, biostimulant applications in the spring can help your turf avoid flush growth and enhance root development. Biostimulant application in combination with proper fertility practices can allow your field to withstand the stresses of spring activities while still producing the root mass needed during the upcoming summer months.
The key to selecting these types of products is to check with other users and purchase them through a reputable distributor. If marketing claims seem too good to be true, they probably are.
Pesticides are also an important part of a field maintenance program. Due to the smaller size of the infield, it is best to use most products on an as-needed or spot-treat basis. Many times, you will need to perform repair work during the season and, if pre-emergents are used, reseeding may be restricted. The best weed control is a dense, actively growing turf. However, weeds, insects and diseases can be found even in the best-managed turf. When these problems occur, proper identification of the pest can be followed up by using the correct product at the label rate.
Remember, there are no magic bullets. It is important for sports field managers to keep good records and communicate with other field managers through state organizations or associations like the STMA (Sports Turf Managers Association). Even more important, don't be afraid to ask questions.
S. Gary Custis, CPAg, is manager of field research and technical services for PBI/Gordon Corp. (Kansas City, Mo.).
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