Tom Cook, Associate Professor
Department of Horticulture
Oregon State University

Introduction

Good quality soccer fields are rare based on my observations of fields in Oregon. Ironically the poor condition of many of the fields isn’t from lack of maintenance inputs. The real problems include lapses in maintenance at critical times of the year and often heroic but misguided attempts at major cultural practices. By performing desirable maintenance practices at appropriate times, maintenance personnel can get the most out of the resources at their disposal. What follows are guidelines for maintenance of fields at levels ranging from professional quality fields to unirrigated youth soccer league fields. I’ve titled the different levels of maintenance as follows: Professional Quality, Good Quality, Budget Irrigated, and Non-Irrigated. For this paper I have used the Willamette Valley in Oregon as the climatic site for recommended maintenance practices. With that in mind the guide will be most useful throughout Western Oregon, Western Washington, and perhaps lower Western British Columbia.

A thought to ponder is that if you asked several “experts” for their opinions on how to best maintain fields you would probably get several different answers. The key is to discern between matters of style and matters of substance. Style issues involve choices of fertilizers, grass cultivars, and which machine does the best job of coring or dethatching. The important point is that people who know what they are trying to accomplish will get good results with whatever machine they use, or whatever fertilizer they apply. When I look at other peoples recommendations, I try to determine if what they advise will work, not whether they advise doing exactly what I would do. Maybe the point is simply that there is no one way to do anything.

Decide what needs to be done and then figure out how to achieve your goals using the resources you have at your disposal. I cringe when maintenance people tell me they knew what to do but they didn’t do anything because they didn’t have just the right machine.

Matters of substance are more important to worry about. Over the years I’ve concluded that soil fields are by nature ” mud holes” and will be generally wet and mushy during the winter season. When I see recommendations to install subsurface drains on these fields to improve drainage I get angry because I know it won’t work. Likewise when I see recommendations for miracle penetrants and soil enhancers I get frustrated because they promise to do things they just can’t do. The old adage that, “if it seems to be too good to be true it probably is,” is appropriate here. With soil fields it is important to accept their limitations and work to get as much mileage out of them as possible. With that in mind please read on!

Top Quality Fields

Most of us probably dream about the mythical perfect soccer field that is smooth, flat, dense, and green. With a perfect profile and grass mowed short it plays fast, gives perfect bounces, and is easy on the players feet. Well, you can forget about perfection because we are starting with a native soil profile and soil fields will never be perfect. What follows are my recommendations for cultural practices that can give the best possible soil base field. To be honest, I doubt that even most pro’s get to do all of the things I will list. The real purpose is to create a model against which you can judge your current maintenance practices.

1. Mowing

Mow 2 times per week April through October.
Mow weekly February through March and November.
Mow as needed during December through January.

Total projected mowings per year = 70.

2. Clipping Removal

Sweep, vacuum, or otherwise remove clippings from the turf after each mowing from April through October.

Projected clipping collections per year = 56.

3. Fertilization

Fertilize with an N-P-K ratio approximating 5-1-4. Use products containing mixtures of soluble and controlled release nitrogen. Slow release sources such as Nutralene, IBDU, Polyon, Tri-Kote, Poly-S, etc., are products of choice.

Avoid straight soluble sources to avoid flush growth and peak and valley growth.

Time applications for mid-spring, early June, mid to late July, mid September, mid-October, and early December, depending on turf vigor and appearance. With a consistent application schedule, rates of 1lb N / 1000 sq ft per application, should be adequate to produce acceptable turf. Turf under low fertility may require up to 2 lbs N / 1000 sq ft to achieve acceptable turf quality. Actual application rates and frequencies will vary for every field and can only be determined by observing turf performance.

If you fertilized a field that is 75 yds by 110 yds at a rate of 1 lb N/ 1000 sq ft you would need approximately 75 lbs N. Using a 25% N fertilizer, you would need 300 lbs of fertilizer for each application. Six applications per year with a 25% N product would require 1800 bs of fertilizer.

4. Overseeding with Perennial Ryegrass

Plan on one to three overseedings per year. Overseed the entire field at least one time per year. Target seedings on areas such as goal mouths, and field centers are acceptable if the rest of the field is in good shape. In years when play destroys significant areas, reseeding should follow tilling and regrading.

Overseeding rates:

• General overseeding, modest wear = 5 lbs seed/ 1000 sq ft (5 lbs seed/ 1000 sq ft) X (75,000 sq ft/ field) = 375 lbs seed/ field/overseeding
• Target overseeding heavy wear areas = 10 lbs seed/ 1000 sq ft

Timing for overseeding:

• General or target overseeding after the fall season is over.
  • Do this even as late as mid to late November.
• General or target overseeding in early spring
  • Do this around spring break on school fields, or early April on non school fields.
• General or target overseeding in late spring
  • Do this in June as soon as school is out or when the spring season is over.

5. Coring

Coring soil fields frequently is important for minimizing surface compaction and improving infiltration of irrigation water. Core fields 3 to 4 times per year with conventional 0.75″ hollow tines. Sweep up cores, drag and mow cores, or use a core pulverizing machine to break up cores.

Time coring for late March to mid April, once school is out in June , mid August before fall sports begin, and at the end of the fall season if the field is firm enough to drive on. Avoid coring during the playing season to avoid objectionable debris on the field during play.

On fields with a history of poor drainage consider vertidraining rather than coring during the June and / or August periods. Set vertidrain solid tines to a depth of 8″ to 12″ or as deep as possible up to those depths.

6. Topdressing

Topdress fields 4 to 5 times per year using golf green quality sand. Apply sand with machinery designed for that purpose avoiding large vehicles such as dump trucks. Rutting caused by dump trucks does more damage than good. Time topdressings during spring through fall when the fields are drier and less likely to be rutted by equipment. Topdress before irrigating, not after.

As used here topdressing serves to firm and smooth the field and helps provide top quality surfaces. Topdressing does not improve drainage.

Each topdressing should total approximately 0.25″ per application. A sequence of 5 topdressings per year will put a maximum of 1.25″ of sand on a field. A realistic target is about 1″ of sand per year for two to three years followed by 0.5″ to 0.75″ annually after that.

Total volume of sand required per year for a 75 yd by 110 yd. field:

• Assuming 5 applications per year at 0.25″ each for a total of 1.25″ comes to around 300 cu yd. / field / year For a single application on a regulation soccer field, plan on approximately 60 cu yd. of sand.

7. Thatch Removal

Once per year in conjunction with overseeding and coring use a flail or solid blade dethatcher to remove organic debris that has accumulated at the surface. This debris is often composed of fresh grass parts that have been ground into the surface via players cleats. In that regard it is different than thatch we might see in an undisturbed lawn. Its important to remove as much of this material as possible to prevent development of an organic bog that becomes anaerobic and causes the surface to become impervious to water.

Dethatching is best timed in June when the soil is firm and relatively dry. A typical sequence of activities might include coring, dethatching, debris removal, overseeding, topdressing, and finally fertilization.

Final Notes

The preceding discussion focused on active maintenance practices. Another strategy useful for soccer fields needs to be addressed in this paper because it can have a profound impact on all fields regardless of how they are maintained. This revolutionary strategy is called many names but I’ll call it FIELD ROTATION in this paper.

Field rotation involves moving goal posts several times per season so games are always played on live green grass. To do this effectively, goals need to be designed so they can be moved by two people in a reasonable amount of time. In addition, field maintenance people need to be geared to stripe fields quickly and accurately so the new lines are easy to see. The best way to do this is to use paint for stripes instead of killing out permanent stripes at the beginning of each season. My suggestion is to design fields more or less square and larger than needed so goals can be moved at least one goal width to the left and one goal width to the right of center and 5 yd. forward or back. If all these positions were used in one season, there would be 9 different field configurations possible. This would increase the time period in the fall when games are actually played on green grass. It would also reduce the tendency of goalies to dig large craters at the goal mouths which require major repairs at the end of the season. Even if fields were moved only three times per season the impact on field quality would probably be significant.

I see this simple strategy as the cheapest and most effective way to extend the functional life of turf on most soccer fields. Unfortunately, when I mention it to soccer clubs they reject it almost out of hand. It seems the prospect of building safe moveable goals is too much for most groups to even attempt. I believe there are enough engineers in the world that someone can come up with a simple but effective goal that will withstand kids climbing on it without collapsing and injuring the climbers. Likewise there are lots of different machines that are reasonably priced and capable of striping fields fast.

The hardest part of moving goals and restriping fields is getting organized to do it. In my opinion, there is more than enough organization to implement this strategy in nearly every soccer group I have ever talked to. If the goal is to provide the best possible playing conditions for the kids, this is clearly the most cost effective way to do it. When you consider your options for improving your fields start with basic maintenance and incorporate the simple concept of moving goals. I think you will be surprised at how effectively this combination will improve the quality of your fields.

Good Quality Fields

Good quality fields are typical of the good fields we occasionally see in parks or at some schools. They are green, dense, and relatively smooth. They always stand out in the summer and early fall periods. Once late fall and the rainy season arrive they fall apart but are generally better than most other soil fields in the area. They aren’t as well groomed as professional quality fields but most of us would be happy if they were our fields. As you’ll see, the numbers will change but general care is quite similar to professional quality fields.

1. Mowing

Mow weekly March through October.
Mow as needed November through February.

Total projected mowings per year range from 40 to 45.

2. Clipping Removal

Sweep, vacuum, or otherwise remove clippings from turf after each mowing from April through October.

Projected clipping collections per year = 28

3. Fertilization

Fertilize with an N-P-K ratio approximating 5-1-4. Use products containing mixtures of soluble and controlled release nitrogen. Slow release sources such as Nutralene, IBDU, Polyon, Poly-S, ESN, or similar products are products of choice. Straight soluble sources should be avoided during the main growing season but may be useful during late fall to enhance winter growth. Time applications for mid-spring, early June, mid September, late October, and mid to late December, depending on turf vigor and appearance. On healthy turf, rates of 1 lb N / 1000 sq ft per application, should be adequate to maintain functional turf. Turf that is weak may require up to 2 lb N / 1000 sq ft to achieve acceptable turf quality. Actual application rates and timing will vary for every field and should be based on observation and your judgment.

Using a 25% N fertilizer applied 5 times per year at 1 lb. N / 1000 sq ft on a full sized soccer field you can plan for 1500 lbs fertilizer / year.

4. Overseeding

Plan on using enough seed to over seed the entire field at least once. Most of the time overseeding will take the form of target seeding heavy wear areas such as goal mouths and field centers. In years when use destroys turf completely and grades are ruined by wet weather play, plan on tilling and grading affected areas and reseeding rather than simply overseeding.

Overseeding rates:

General overseeding = 5 lbs seed / 1000 sq ft

Plan on 375 lbs seed / full size field

5. Coring

Core fields 2 to 3 times per year with conventional 0.75″ hollow tines. Sweep up cores, drag and mow cores, or use a core pulverizing machine to break up cores.

Time coring for late March to mid April, once school is out in June, in mid August before fall sports begin, and at the end of the season if the field is firm enough to drive on.

On fields with a history of poor drainage, consider substituting vertidraining during the June period. Set vertidrain solid tines to a depth of 8″ to 12″ or as deep as possible up to those depths.

6. Topdressing

Even on good fields it is generally not feasible to topdress consistently. Topdressing is a labor intensive activity that few schools can even consider. What I generally see is sporadic heavy topdressing that does more harm than good. The few park departments I know that have attempted topdressing, have rarely been able to sustain the effort more than 2 to 3 years. Results are generally promising if you can sustain a program at least 3 years, otherwise it’s not of much value.

A single field topdressed 5 times at 0.25″ per topdressing requires approximately 300 cu yd. of sand. Plan on about 60 cu yd. for a single topdressing.

To get the most mileage out of a topdressing program concentrate applications in the dry months from April through August. Shoot for monthly applications of no more than 0.25″ each. The goal is to build up a fairly uniform layer of sand prior to the wet season.

7. Thatch Removal

Once per year in conjunction with overseeding and coring, use a flail or solid blade dethatcher to remove organic debris that has accumulated at the surface. Removing thatch helps prevent development of an organic bog that plugs the surface and often contributes to the anaerobic stench common on sports fields.

Dethatching is best timed in June when soil is firm and relatively dry.

A typical sequence of activities might include coring, dethatching, debris removal, overseeding, topdressing, and finally fertilization.

Budget Irrigated Fields

These are typically poorly maintained fields, with permanent bare areas in goals and field centers. Often grass is not watered in summer until a few weeks before play begins. In some cases the water is turned on in spring and not turned off until late fall. As a rule these fields are not routinely overseeded, are rarely fertilized, are occasionally buried under heavy sand topdressings, and provide poor quality surfaces to play on. They are among the first fields to lose grass and mush up in fall. In short they are the most typical fields I see.

As I see it these are the fields that will benefit most from a well thought out and creatively planned maintenance program. Every shot counts in maintaining these so they provide functional playing surfaces. The following guides will vary significantly from the professional and good quality field guides.

1. Mowing

If you can’t do anything else, try to keep these fields mowed at least weekly. This is most important during the summer months. Summer mowing will insure that you have the best turf possible in fall.

Mow weekly March through October.
Mow 2 times per month in November and February.
Mow at least monthly in December and January.

Total projected mowings add up to 38.

2. Clipping Removal

Don’t worry about removing clippings on these fields.

3. Fertilization

Do what you can to get these fields fertilized. Concentrate on fertilizing spring through summer to get fields back in shape by fall. Use primarily soluble or mixed soluble – slow release products. Products based on SCU ( sulfur coated urea ) offer good initial and fair residual response at relatively low cost. Look for products approaching 5-1-4 ratios for N-P-K. Co-op’s and other fertilizer suppliers can often custom blend to your specifications.

Timing: Mid to late April apply 1.5 lbs N / 1000 sq ft

Early June apply 1 to 1.5 lbs N / 1000 sq ft
Early September apply 1 to 1.5 lbs N / 1000 sq ft

Total fertilizer required assuming 4 lbs N / 1000 sq ft / year using a 25% N product = 1200 lbs fertilizer.

Note: Don’t get into the habit of routinely applying 15-15-15. While it works okay, it is a waste of Phosphorus and may be more expensive per pound of Nitrogen.

4. Overseeding

All overseeding on these fields should be targeted at wear areas.

Use perennial ryegrass for overseeding. There are at least 90 good cultivars so there is no need to get confused about which is the best.

Just remember to avoid ” LINN “ and un-named common types.

Target overseed wear areas at the end of the fall season if the field is not too torn up. If you simply broadcast the seed, there is a good chance it will germinate and fill in before spring sports start. It is always worth a try because if it works you are way ahead in spring.

When worn areas are not overseeded they eventually become dominated by annual bluegrass which on these sites often behaves as a winter annual. It actually looks good in late winter but then dies in late spring, leaving you with bare ground again in summer.

If the wear areas are too torn up to simply overseed, wait until late spring and till and regrade the areas before seeding. If you have to import soil to get the surface back to its original grade, use soil similar to what is already there. Tilling in or layering two or three inches of sand on soil doesn’t accomplish anything and may make it more difficult to get new seed to germinate. Tilling and regrading is more effective than burying dead grass with a heavy topdressing and trying to seed over that. If you take the approach of tilling and grading you will probably find it is something you will do once every few years because you generally will have better turf year around. Healthy turf will hold up better than weak turf.

If you overseed in fall and don’t get a catch, come in during spring or early summer and slice seed the area with a tractor mounted machine.

The main point is to make regular overseeding an important part of your maintenance program. It will go a long way towards improving year around turf quality.

Overseed at rates of 5 to 10 lbs seed / 1000 sq ft, using the heavy rates in fall or when you have a short time frame to get turf ready for play.

At the 5 lb rate plan on using 375 lbs seed to overseed a full size soccer field.

5. Coring

Core as many times as you can manage each year. Realistically that will probably be 3 times a year if you are really dedicated. Use conventional 0.75″ hollow tines, and drag or mow the cores to break them up. Time coring for spring break, again when school is out, and one more time in late summer before fall sports begin. Don’t core if it is too wet to safely drive you tractor across the field. Under real wet conditions you do more damage to the field than good.

Every other year contract to have the field cored with a vertidrain to get deep penetration. You’ll be surprised at the improvement in turf performance.

6. Topdressing

Topdressing has limited value on budget fields because it needs to be done on a light and relatively frequent basis. Use your time, money, and people for basic maintenance practices instead. Poorly conceived topdressing efforts are one of the most common screw ups I see on school fields. Usually what happens is you make a heroic effort to round up the dump trucks and some reject concrete sand and bury the turf throughout the field. Dragging usually moves the sand into the tire ruts and leaves you with 2-4 ” of sand in some areas and none in others Now that you have smothered the turf a lot of it dies so field density is reduced. You increase irrigation to speed recovery and find the sand dries out quickly while the original soil becomes wet and mushy. Recovery is slow, field quality declines, and by fall the fields are not ready to play. In short, you wasted a great deal of time and effort and accomplished nothing.

Instead of topdressing, concentrate on good old fashioned turf culture!

7. Thatch Removal

Once a year find a flail mower and set it down low so you can effectively dethatch and do some minor surface grading Follow dethatching with slice seeding and fertilizer then water thoroughly. June about the time school is out makes for good timing, provided you keep the field moist enough to get good germination of the perennial ryegrass. This is much more effective than topdressing as described above and is probably less expensive.

Budget Non-Irrigated Fields

Sadly there are a lot of non-irrigated fields that are being used for kids soccer. Ironically, when I am approached by people about installing irrigation on these fields, I usually tell them not to! The reason is not that I don’t like kids. The reason is that these fields are generally maintained by volunteer groups and lack the resources needed to maintain irrigated fields.

In fact they can barely maintain unirrigated fields. My point is that as soon as fields are irrigated they need to be mowed all summer long and ultimately need a lot more inputs. I try to emphasize that before they start irrigating they need to get geared up to do the maintenance that will be required. At that point the conversation ends with them being disheartened and me feeling like a villain.

So what can be done with non-irrigated fields? I think they can be a lot better than most are, if you do the right maintenance practices at the right times. Remember that even though these fields will never be great they can be functional and have a complete cover of grass.

1. Mowing

Find a way to get these fields mowed regularly. Don’t depend on already strapped school district maintenance personnel to go out of their way to help you out.

Mow weekly from September through November.
Mow 1 to 2 times per month as needed during December through February.
Mow weekly March through June.
Mow every two weeks July through August.

Total projected mowings adds up to about 36.

2. Fertilization

Fertilizer is an important tool on unirrigated fields. Summer drought stress will always leave fields weak as fall soccer begins. By the end of fall most of these fields will be very thin and torn up. Fertilizer applied at the onset of fall rains will stimulate grass during the season. Another application in early December or just after the season ends will maximize growth through winter and provide dense turf for the spring season. Fertilizer applied in early spring will help turf handle wear in the spring season. If June is wet you can even fertilize then to develop dense turf prior to the summer stress period.

Fertilize with an NPK ratio approximating 5-1-4. Fertilize with soluble or mixed soluble-slow release fertilizers. Keep in mind that on these fields you generally want to stimulate growth to aid recovery from drought or wear.

The early and end of season applications should each be about 2 lbs N / 1000 sq ft. The early and optional late spring application can be at lower rates if turf is in good shape. Plan on 1 to 1.5 lbs N / 1000 sq ft at these times. The late spring application should only be applied if there is adequate rain to dissolve it and wash it into the soil where turf can use it.

With a 25% N fertilizer applied 3-4 times per year, plan on 5-6 lbs of N per year. This adds up to about 1500 to 1800 lbs of fertilizer per year for a full size field. If this is more than you can afford, drop the late spring application. The fall and late fall applications are the most important so don’t miss them.

3. Overseeding

Every summer drought will cause severe thinning of turf on unirrigated fields. What is left may be further destroyed during fall play. Overseeding is important if you hope to maintain turf density at an acceptable level.

Without irrigation you have to rely on natural rainfall for germination but temperatures are often too low for good growth during the rainy season. It seems like an impossible task. Fortunately we have perennial ryegrass which germinates and grows fairly well even in cool weather. Established in late fall, it can often survive the drought the following summer. That implies that regular overseeding every fall can actually increase turf cover over time.

In all but the driest years that is exactly what happens.

The key in overseeding non-irrigated fields is to be realistic about what you can achieve. It will always be two steps forward and one step back!

Target or general overseed each year at the end of the fall use period. If the field is firm enough to drive on, overseeding via a tractor mounted slice seeder is a great way to go. If that’s not possible, broadcast on the surface and take your chances. The key areas are always the heavy wear sites but general overseeding the entire field is a good idea.

General overseed at 5 lbs / 1000 sq ft and raise it to 10 lbs / 1000 sq ft for target areas such as goals. One scenario involves slice seeding the entire field followed by broadcast seeding the heavy wear areas.

Timing is pretty simple. Late fall works best because it gives the perennial ryegrass the most time to establish before summer drought hits it. Spring seedings often come up just fine but mortality is high when drought comes in summer.