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In the previous issue of the H&K Maintenance Minute we discussed the drainage of infield skin areas. But drainage is also a common problem on the grass portions of a field. If muddy conditions are present, the field becomes unsafe and can warrant cancellation of games and practices. The cause of most drainage problems are fairly predictable. First we’ll briefly review surface drainage. Then we’ll examine ways to help water move into the soil more quickly.

As with skinned infields, surface drainage is the first concern on grass areas. The field must be sloped at a minimum of 1% so that excess water will flow off the field. Even if the general grade is correct, any small undulations in the surface will cause water to “pocket” and form puddles. Sometimes these low spots can be corrected by topdressing with a thin layer of high-quality topsoil. If done a few times per year this practice can disperse the water and allow it to flow along the grade. Larger undulations will require removal of the vegetation and re-shaping of the field contours.

puddle-450

Figure 1: Puddles often in the low areas of a field during rain events. These water pockets are common on high-wear portions of the field, such as soccer goal mouths or the center of a football field.

When sloped properly, excess water will run off the field. However, wet conditions may still persist if the soil is overly compacted. Soil compaction is probably the number one problem on athletic fields of all types. As pore space is squeezed out of the soil by players and equipment, water encounters great difficulty in moving through the profile. Aerification is the best practice to relieve compaction without complete tillage. A great upgrade to the aerification process is a topdressing of compost. By spreading compost over the field prior to aerification, organic matter can be incorporated into the holes when you drag the cores back in. The addition of organic matter will help build soil structure. Soil structure is the binding of small silt and clay particles together into larger aggregates. These aggregates act like sand-sized particles, which restores pore space to the soil and improves infiltration and percolation.

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Figure 2: Applying a thin layer of compost prior to aerification will condition the soil to provide better soil structure and more porosity.

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Figure 3: Soil structure is key to ensuring proper drainage on native soil fields.

Soil compaction is inevitable on any field receiving frequent usage. A more expensive but highly effective strategy to combat soil compaction is the installation of a sand cap. By repeatedly spreading small amounts of sand over the field, a layer of coarser material is built over the native soil. The grass slowly migrates upward through the material, so there is no need to re-establish the turf. The benefit of a sand cap stems from the inherent porosity of sand- even under the compactive forces of field usage, sand will retain large pores which help transmit water rapidly. Installing a sand cap can help reduce the risk of your field being ruined by just a single “mud bath” game, because it can be played on shortly after (or even during) a heavy rainfall. It is essential to use the correct type of sand- unfortunately, most construction or masonry sands from your local quarry are not suitable for athletic fields. Once established, the maintenance costs for this type of field are higher since it requires removal of aeration plugs and maintenance applications of sand topdressing.

sand-cap

Figure 4: This profile of a sand-capped field shows the layer of coarser-textured sand overlying the finer-textured native soil.

One final practice that warrants mention is the attempt by some field managers to till sand into their fields. This practice is not recommended unless your field already contains over 70% sand (very rare in Wisconsin). While sand by itself does drain well, tilling sand into fine-textured soil is akin to adding 3 or 4 marbles to a jar of flour. Imagine water flowing through this jar- unless the marbles are touching each other (“bridging”), the flour will simply fill in all the space around the larger marbles, preventing water from flowing through the jar. To dilute the fine soil sufficiently, so much sand would be required that it would make more sense to completely excavate the native soil and install a sand-based rootzone. 

marbles-flour

Figure 5: Tilling sand into a native soil field is unlikely to provide a significant benefit, just as adding only a few marbles to a jar of flour has little effect on the jar’s pore space.

Remember, surface drainage is always the first priority- any attempts to improve drainage must first include a proper surface grade. Next, consider ways to reduce soil compaction- aerification along with compost topdressing is one; the installation of a sand cap is another. Our third and final installment on drainage will focus on installed drain systems for grass areas! To inquire about drainage considerations at your facility, contact H&K’s Evan Mascitti at evan@HKSportsFields.com.

“My field doesn’t drain!”

This is the most common gripe we hear from coaches and facility managers. A wet field means unsafe playing conditions, lost revenue, and re-scheduling headaches. In this three-part series of the H&K Manintenance Minute, we’ll examine the largest barrier to quality athletic fields: drainage.  First, we’ll cover the non-grass portion of the field, known as the “skin.”

The only way to remove excess water from an infield skin is with a proper surface grade. Water always flows along the path dictated by gravity- and it is far easier for water to move across a surface rather than through it. When water flows along a slope, it encounters little resistance. On the other hand, when water flows through a porous medium- be it stone, sand, or soil- the water must move around the individual particles. Along its path through the profile, the water encounters frictional and attractive forces from the soil particles. Therefore our goal is to move as much water off the surface as possible, so as little water as possible has to go through the surface.

surface-flow-infiltration

Figure 1: On native soil athletic fields, the surface grad is vital because water always moves quickly along the surface than through the soil.

Many people believe that installing a system of sand trenches, gravel layers, or pipes beneath the infield dirt will reduce rainouts. Unfortunately, thousands of dollars are wasted each year based on this idea, which couldn’t be further from the truth. The soils used to construct infields are too fine-textured and too compacted for water to seep through to the drainage gravel or pipes. The system never has a chance to transmit water away from the field, because the water can’t even get into the pipes. The only way to get water to “drain” from an infield skin is to slope the surface correctly and allow gravity to work its magic. Additionally, poor-quality soil is commonly used on baseball infields which can cause the field to retain too much water. Infield soil amendments will be addressed in a future issue.

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Figure 2: Drainage systems beneath skinned infields is an un-needed expense because water will never reach them.

The surface grade of an infield skin is most often compromised near high traffic areas- where the base runners slide and take their lead-offs, and also where the infielders stand. As players walk, run, and field ground balls, soil is slowly but surely displaced from these areas. The material is carried off the field on players’ cleats, equipment, and uniforms, and it may wash into the grass areas of the field during rain storms. These processes happen so gradually that they are often hard to perceive. Eventually though, the low spots will become large enough to collect water and prevent proper surface drainage. Small areas can be repaired by scarifying the surface, adding material to level the depression, and re-compacting the soil. For more severe undulations, the entire surface must be re-graded with a tractor and laser-leveling equipment. Any buildup of soil along the “lip,” where the dirt meets the grass edge, also must be removed to permit water to flow uninhibited from the dirt to the grass.

lip-buildup

Figure 3: Low spots typically form around bases, position areas, and the back arc of the infield skin.

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Figure 4: Laser-guided grading equipment fills in low spots on the infield and allows water to drain off the back edge.

In the next two articles, we’ll discuss ways to improve drainage on grass areas. For more turf maintenance tips, stay tuned for future editions of the H&K Maintenance Minute, or contact H&K’s Evan Mascitti at evan@HKSportsFields.com.

Soil compaction is inevitable on most sports fields. Open pore space which normally holds air and water is squeezed out of the soil by athletes running, jumping and sliding on the turf, and by traffic from mowers and other equipment. As soil porosity is reduced, the grass thins and the field becomes hard as concrete. Somehow, we must relieve soil compaction to soften the surface and help the grass recover.

In the world of agriculture, soil can be cultivated with a subsoiler, plow, or other implement to loosen the ground. As turf managers, we aren’t able to till the soil without killing the existing grass and taking the field out of play for several weeks. Instead we aerate, or aerify, the turf to relieve soil compaction, one hole at a time. As the name suggests, the primary goal of aerification is to re-introduce air to the soil. Grass roots need air just like people do- if the soil doesn’t have enough pore space, the roots will suffocate and the above-ground turf will suffer. 

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Figure 1: The exchange of air between the soil and the atmosphere is vital for healthy turf.

There are many types of aerification equipment, but most fall into two basic categories: hollow-tine and solid-tine. Hollow-tine aerification (also known as “core” aeration) is the best practice to relieve soil compaction on a sports field. This type of aerification is best performed at moderate soil moisture. The most effective machines use a piston-type action to remove very clean soil cores without tearing the turf. Drum- or wheel-type machines can also be used, but they produce much more surface disruption and are not as effective at relieving compaction.

piston-type-aeration

 Figure 2: A machine utilizing piston-type action and hollow “coring” tines is the most effective type of aerification.

Another type of aerification is with solid tines or spikes. This practice simply pokes holes in the soil. Because solid-tine aerification does not remove a soil core, it actually creates more compaction along the walls of the hole. Solid-tine aerification can be used during the playing season to help improve air entry into the soil, but it is not a substitute for core aeration.

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Figure 3: Solid and hollow aerification tines in various shapes and sizes

How often should you aerify your fields? On high-use fields found at schools and parks, once or twice a year is a minimum number of aerification events. Even better would be 4 or 5 times- you really can never aerify enough on these types of fields. With each practice, game, and tournament the compaction process begins again. I once heard the turf manager at a large soccer complex say he always had an aerifyer running somewhere on his grounds. Of course, it is best to perform aerification when the field is out of play, to minimize the impact of surface disruption.

Aerification is essential for healthy turf and to produce a safe playing field. In future editions of the H&K Maintenance Minute, we’ll examine other simple turf management tips to help your field sparkle! For more information on turf maintenance tips, and the aerification services H&K Sports Fields offers, contact Evan Mascitti at evan@HKSportsFields.com.