The Art of Infields

The first thing that strikes your eye when watching a big league baseball game is the turf: the bright green grass, razor sharp edges and detailed mowing patterns. The players, however, have their eyes on the dirt. Seventy percent of baseball's action takes place on the “skinned” areas of the field. The outfielders play only half of the game on the grass. The infield dirt is what makes or breaks a field.

Turfgrass management is a complex science. Several universities offer degrees in it and millions of dollars are spent each year researching it. But maintaining a quality-skinned infield is an art that you can learn only on a ball field. There has been an increase in research in the last few years, but in order to really find out what you need to know about it, you have to roll up your sleeves and get down in the dirt.

CHOOSING INFIELD SOIL

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The most important ingredient in infield soil is the base soil. The base should be 4 to 6 inches deep and packed tightly, but not too tightly. You should still be able to till it with moderate agitation. To create an acceptable base soil, you first need to evaluate the current percentages of sand, silt and clay. A good starting point is a soil with 60 percent sand, 15 percent silt and 20 percent clay. Too much sand will prevent the soil from packing tight enough and will cause low spots in the high-traffic areas. Too little sand will make the infield a mud bog after a rain and too hard in the heat of the summer. Silt and clay, when combined with water, are the glue that holds the soil together. These two combined should be less than 50 percent of soil makeup. (For tips on evaluating soil makeup, see “Determining soil texture,” below.) It is important for you to have the soil tested. There are several labs around the country that can do these tests.

DRAINAGE

The most critical element in infield drainage is the surface grade. The composition of the soil can make the sub-surface drainage ineffective. If the soil is too tightly compacted it will not allow water to pass through, and skinned infields will drain at less than 1/10 inch per hour. The only way to effectively remove excess water is to set the grade so that water flows off at the surface. One half of one percent of fall from front to back will accomplish this.

After you establish surface grade, the most important aspect of drainage is managing the transition from the turfgrass to the dirt, or the “lip.” A perfect grade will not be effective if you allow a lip to build up too much around the infield perimeter. The infield soil should be level with the root-zone soil, not the top of the turf. There are many reasons that malformed lips develop. Erosion from wind and water move the infield soil and deposit it in the turf. Improper or neglected maintenance will compound the problem. Regular, scheduled maintenance will prevent the need for a major renovation.

The most effective method for preventing lip build-up is to sweep out the edge on a daily basis. While this is ideal, it is not practical for most maintenance crews due to manpower and budget constraints. Using a backpack blower on a weekly basis and hosing on a monthly basis is probably more realistic. To correct major lips, you often have no choice but to remove the turf, re-establish the grade and replace the turfgrass.

MAINTAINING SURFACE GRADE

Once you've discovered the optimal soil consistency, establishing a good surface grade is your next step. A common practice is to hire someone to laser grade your field before play begins in the spring. If this fits in your budget, do it. However, there are less expensive ways to do this. One way is to check the grade using string lines. The first step is to make sure that all the lips are the proper size. Run a string line from the front edge to the back edge of the infield. This line should be very tight and make contact with the turf on both ends. Stand to the side and look for spots where the string is touching the infield. Using the flat edge of a landscape rake or a leveling board, scrape the high spots first and work the excess into the low spots. With a little practice and a lot of patience you will quickly become proficient at this. Move the strings over five to 10 feet and work your way across the field. Level the base paths with a 2 × 4, using it as a screed board. Loosen the soil with a nail drag, level and roll. Regularly scheduled maintenance to maintain the surface grade will prevent a big problem down the road.

TOPDRESSINGS

Infield topdressings, or conditioners, come in all shapes, sizes and colors. Their main benefits are moisture management, improved texture and appearance. Calcined clay has been the most widely used by field managers for a number of years. It is capable of absorbing large amounts of water and gradually releasing it back into the soil. It works well as an amendment in the soil and as a topdressing. Vitrified clay is rapidly gaining favor among groundskeepers as a topdressing. Its reduced absorption rate allows water to pass through to the base soil. Crushed aggregates are also commonly used in some parts of the country. These are usually ground stone dust or brick dust. Choosing the right topdressing for your particular soil should involve some experimentation. The combination of calcined and vitrified clays is becoming very popular. Particle size and color choices add to your possibilities. Try different combinations until you find what works best for your budget, the field and your team.

Calcined clay is also used as a drying agent on wet fields. You can spread it on wet or slick areas of the field to improve footing and absorb excess water. Organic products made from corncobs are also made for just this purpose. These will absorb tremendous amounts of water but should be removed as soon as possible.

SPIKING AND DRAGGING

Spiking and dragging are the most frequent maintenance tasks for sports infields. When done properly, they will help to maintain the surface grade, drainage and provide a safe, resilient playing surface. Spiking, or nail dragging, fluffs the soil and provides loose material to fill divots and low spots. To maximize the effectiveness of this procedure, do it when oil is moist, not wet. For daily maintenance, only spikes deep enough to remove spike marks and bumps. Stay six to 12 inches away from edges and use hand drags in tight areas.

Mat dragging, or leveling, is a similar process. Speed control, especially on turns, is critical for a quality job. Using excessive speed while turning will sling soil to the outside of the field, causing potential grade and drainage problems while the proper speed will aid in cutting down high spots and filling low spots. Keep screen drags at least six inches away from all edges. These you should do by hand with a rake or a drag broom. Always rotate your starting and stopping points. Try to start on a high spot and end on a low area. You should also level base paths by hand whenever possible due to their narrow width. A periodic rolling will keep them firm and stable. Regularly trimming the grass edges will give a crisp appearance and help keep lips under control.

MOISTURE MANAGEMENT

Water is the glue that holds the whole thing together. You can have a firm, tightly compacted soil and with the proper moisture content it will play “soft.” Moist soil is easier to work and will be more resistant to wind erosion. So the question looms, “How much water do I put on the skin?” This, more than any other aspect of infield management, is where the art comes in. There are several things you must consider. First and foremost is the weather. The temperature, humidity, cloud cover, chance of rain and wind are all factors you will be dealing with. Other considerations include the amount of time before the game starts, the forecast for game time and the rate at which the skin will absorb water. You should take all these factors into account when watering. Only experience will be able to guide you. It takes hours of practice to be able to apply water evenly. This is just as important as how much water you apply. A consistent, uniform watering will promote a consistent, uniform bounce. Deep watering after the last game of the day will help the next day's work go smoother.

MAKING YOUR MARK

The best thing about maintaining a baseball field is that you get to put your own personal touch on it. Each one has its own character and look that distinguishes it. And you get to use your imagination. A well-groomed ball field is truly a work of art.

Tom Burns is director of grounds for the Texas Rangers in Arlington, Texas. You can reach him at (817) 273-5050 or by e-mail attburns@texasrangers.com.

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