What should the standard for infield mix be? What adjustments from your standard can be made for skins being managed on low budgets? What questions should readers ask of their material suppliers to help get the best results?
Setting a realistic standard for infield mixes: opinions from the experts
Last year we heard from an exasperated, high-profile groundskeeper who was fit to be tied about an article we ran that discussed silt to clay ratios for infield skins, among other topics. In response, we asked a number of industry professionals to answer these questions: What should the standard for infield mix be? What adjustments from your standard can be made for skins being managed on low budgets? What questions should readers ask of their material suppliers to help get the best results? Here are their responses:
Bill Deacon, director of landscaping and field operations, New York Mets/Citi Field
What should the standard for infield mix be? I believe that the sand, silt and clay percentage should be determined by the level of maintenance that you are capable of doing. As a general guideline you would have lower level maintenance fields in the 70-75% sand and 25-30% silt and clay with the clay being slightly higher than the silt; intermediate fields in the 65-69% sand and 31-35% silt and clay with clay slightly higher than silt; and the professional level 60% sand or slightly below with the corresponding silt to clay amounts, but again with the clay being just slightly higher than the silt.
I think when looking at infield skins the silt-to-clay ratio is very important and should be in the 0.5-1 range. I also believe that the medium sand content is important; the medium sand would be the first three sand values on a particle size analysis test, the 1mm, 0.5mm and 0.25mm numbers added together, and you would like to have that number at 40% or above. I also believe the gravel should be below 3%.
When managing a low budget infield skin the most important thing is to have a well-balanced soil and identify how much time you will have to maintain it and if you will be able to water it. Water the skin as much as possible, but if you can’t water at all then I would personally like to be in the 70-75% sand range, even if I can only water it a little and don’t have much time for maintenance I would want to be in the 70-75% sand range. I would spend the small amount on a test and remember you can always amend an existing infield skin to get it into the range of maintenance that is best for your situation.
I would budget to have it laser graded once a year if possible to help with low spots and any puddles. It is also important to have your infield graded, installed or amended correctly, this will alleviate future headaches. In a rainy climate you want to have some kind of slope on your infield to move water off of it, in the 0.5%-1% range. Try to be creative with your maintenance, ask the teams or parents to rakes dirt chunks off the edges and drag it if there are no staff members there that day.
You also must manage expectations, no infield skin is maintenance free but maintenance is easier if it is a good quality material. The last thing is ask questions of different people, I ask people constantly about their maintenance practices, and be positive, no one ever had a good infield skin with the attitude that they can’t do any better than it is.
What questions should readers ask of their material suppliers to help get the best results? Do you test your infield mix and if so is it an independent lab and can I see the results? Does your infield mix contain stones and vegetative matter? What do you screen your mix to? If I am not satisfied with the mix can I send it back? Can you send me the same mix every time I order it? Do you have a client list that I can contact?
Luke Yoder, director/field & landscape maintenance, San Diego Padres/PETCO Park
I think for Little League to High School and all in between it should be 70-75% sand and 30-25% combined silt and clay. The SCR should be 1.1-5. The majority of the sand should fall in the medium range. The fine gravel content should fall below 2%.
For a higher maintenance, performing mix you can go anywhere from a 65/35 up to the highest of 50/50. Same rules and numbers apply to that as above. This would have to be custom-ordered for some people, but for others that know they want something with more clay but would not custom order, then they could stay in the middle with a 60/40.
The only adjustment from the standard you can do to make it any easier would be to shoot for the higher sand 75 and lower combined silt and clay, 25. Even this is not going to make a big difference in how it holds up with little or no maintenance compared to a 70/30. The key is getting it installed correctly and then trying to budget for a proper laser 1x a year.
The best thing you can do is have a conversation with them before to get their expectations and let them tell you how much work, time, and water they are willing to put on it. Then share with them educational guidelines for install, renovation, maintenance and make sure they are on board with just how hard it is to maintain a nice infield skin, and that no matter how good your dirt is it can and will still get hard at times and be a struggle. But not nearly as bad if they were to get an inferior mix.
Questions to ask: Can you send me a sample? Can you send me the data? Do a test yourself with the sample you get? Can I come up to your plant and take a look at your operation and take a random sample then? Do you have a list of references for me to call?
Tom Burns, consultant, Diamond Pro/TXI & former MLB head groundskeeper
ASTM’s F2107-08, Standard Guide for Construction and Maintenance of Skinned Areas on Baseball and Softball Fields is exactly what it says, a guide. The document states that the word “Standard” in its title means only that it has been approved through the ASTM process. The physical properties of quality skinned infields at the professional level and the maintenance required to manage them are vastly different than those of recreational fields. However, there is an accepted starting point for the physical makeup that can be adjusted for the level of play and maintenance that the field receives.
The usual starting point for an infield skin is 60% sand and 40% silt/clay. It is desirable to have the silt/clay ratio to be 1/1 to .5/1. The majority of the sand should be in the medium to medium coarse range. We can make adjustments for those on low budgets or limited manpower by increasing the sand content to say, 70%, and keeping the silt/clay ratio as close to the standard as possible. You can also make this adjustment by adding a manufactured amendment such as a calcined or vitrified material to the mix. Although these materials are made out of clays, due to the heating process, they react in the soil more like coarse sand. These adjustments to the mix will help to relieve excess compaction and make it easier to recover from rain events. However, it should be noted that these mixes will be more prone to erosion by wind, water and excessive play, and proper maintenance is critical to maintain the correct grade. They may also consider increasing the grade of the skin to .75% to help drain excess water. First of all, [infield skin managers] need to be honest with themselves and determine what level maintenance they will be able to perform. Do you have a reliable water source? Professional grounds managers spend hours each day managing the skin for one game. I have always advocated that you should try to get your infield mix from a source relatively close to your location when possible. The high cost of fuel has driven transportation costs through the roof.
Know what you want. Ask for a test. If you are on a low budget, you may want to adjust your spec to +/- 5% on your sand, silt and clay. This will get you close to your ideal and may save you money in the long run. Dr. Norm Hummel, Hummel & Co. Having served on the ASTM committee that wrote the current guidelines for infields, I can tell you that it can be quite contentious. Anything you write is likely to stir up a hornet’s nest. Just the same, I have been testing infield mixes for years; hundreds from around the country. Through tying in my testing experience with personal observations in the field as well as feedback from end users, I have come up with these guidelines that I have used in my reports, with a few modifications.
For most fields: Sand content: 65-75%. Ideally more than 2/3 of the sand will fall into the medium and coarse sand fractions (0.25 – 1 mm). A silt to clay ratio of less than 1, preferably between 0.5 to 1. In other words we want at least as much clay as silt. Infields that don’t have access to water and/or are not regularly maintained should be at the higher end of the sand range. Fields in drier climates will want to be on the lower end of this range.
Professional Fields or other highly maintained fields (access to water and routine maintenance, likely tarped): Sand content: 55-65%, with more than 2/3 of the sand in the medium and coarse sand fractions. Silt to clay ratio less than 1, preferably between 0.5 to 1.
A couple of things that are important:
One of the biggest misconceptions with infield mixes is that they must drain. It’s hard for some to understand when I tell them they have to add clay to make their field drain better. I have seen elaborate drainage systems installed under infields that serve no purpose. In other cases they make the mix sandy, thinking that it will improve drainage. The fact is a good infield mix that is properly installed will not vertically drain, at least not very well. Therefore infields MUST be pitched to surface or sheet drain water off of the surface. If that is not the case, birdbaths will form, or in the case of sandy mixes, a quagmire. Laser guided grading is recommended. Also, the infield mixes should be compacted when placed, again to prevent vertical drainage and facilitate surface drainage.
Paul Zwaska, general manager, Beacon Athletics & former MLB head groundskeeper
For many years, it was believed that a 60% sand, 20% silt, 20% clay was the optimal infield soil. And in many cases it is. But I have tested many infield soils through the past 25 years that failed even though those percentages were met. Through continued trial and error and evaluation, the shortcomings were uncovered and adjustments were made to the generally accepted beliefs.
Sand in an infield soil provides the structural integrity in the soil much like the skeletal system provides the structural integrity of the human body. Sand is needed in the highest amounts in the soil to create the proper structure. However, it can’t be any sand. In order to have the proper structure for what we desire to use the infield soil for, we must look at the distribution of the various sand particle sizes more closely.
In the past decade, it has come to light that an infield soil performs best when the majority of the sand in the infield soil is in the medium to very coarse range. The amounts needed depend on the level of maintenance these fields will see. In general, the lower the maintenance level, the higher the volume of sand, especially that of the medium to very coarse range. What is equally important is that the amount of fine to very fine sand in the soil be kept at a low level. High amounts of the finer sands is one area where many harvested infield soils have failed in the past, even those that had the right overall percentage of sand, silt and clay.
For a professional level soil, which usually sees a high level of maintenance, the overall sand content should fall in the upper 50 to lower 60% range. The medium to very coarse sand content for the professional level should be between 38 to 45%.
Silt has had its share of blame in bad infield soils and rightfully so, for too much silt creates serious problems in infields. I have tested infield soils from all over the US, and unfortunately, most have too much silt. Because we use mostly medium to coarse sand in the infield soil with just small amounts of fine to very fine sand, there is still a fair amount of large pore space left that needs to be filled to provide the proper soil density. If we leave too much pore space in the infield soil, it may not be stable enough for the soil to provide the proper traction for the player.
To return to the human body analogy, silt is like the organs that fill the large cavities of our skeletal system like the brain, heart, lungs, liver, and stomach. In the past, silt was looked at as its own entity in the soil; however, in recent years we have come to understand that for proper density, the silt needed to be looked at in concert with the amount of clay in the soil. Clay is the glue that holds soil together and keeps silt under control. It has been determined that the silt content in an infield soil should ideally equal half the amount of clay to as much as equal to the amount of clay.
To make this easier to understand, the Silt to Clay Ratio, or SCR as it has come to be known, was developed to make it easier for groundskeepers to make the decision as to whether their infield soil has the proper amount of silt and clay. The SCR is achieved by taking the percentage of silt in the soil and dividing it by the percentage of clay. An SCR of 0.5 to 1.0 is optimum. Infield soils with an SCR slightly above 1.0 to about 2.0 can work provided a topdressing is used in conjunction with that soil to help nullify some of the negative effects of slightly elevated silt content. Infield soils with SCRs greater than 2.0 or less than 0.5 will need some amending with other soils to bring them into balance. So whether you are looking for a professional level soil or something more on the recreational end, the target SCR should always be between 0.5 and 1.0.
If we know that the SCR should always be in the 0.5 to 1.0 range, then adjusting an infield soil to different maintenance levels simply involves adjusting the overall sand levels and the amount of medium to very coarse sand in the soils. For instance, park and recreation fields or school fields that see little regular maintenance or have volunteers working on the field require an infield soil with a much higher sand content. This helps to compensate for the lack of maintenance by keeping these fields a little softer or resilient since they won’t be nail dragged or watered very often and probably have no topdressing on the skin like a collegiate or professional field. These fields will need the overall sand content to be between 70 and 75%. The medium to very coarse sand should make up greater than 50% of the overall soil.
There have been some very big changes in the recommendations and manufacturing of infield soils in the past decade. But we are merely playing catch-up to our equals in the golf industry when it comes to engineering the specific soils we need for our infield skins. Advances by some suppliers in the past 5 years have finally brought what ball field groundskeepers have been clamoring for decades. Infield soils engineered and manufactured to very precise specifications that can be replicated exactly, at any time.
The days of settling for the best harvested soil that you can find in your area will become a thing of the past in the next decade as groundskeepers will be demanding engineered infield soils more and more from their soil suppliers. These balanced soils make managing an infield so much easier. Those suppliers who educate themselves and update their manufacturing will thrive, but it is up to groundskeepers to keep the pressure on suppliers to perform. Groundskeepers have the responsibility of testing their infield soils and those that are supplied to them to know what is in their field and what is being added. You want to know that the soil you are adding is improving the makeup of the skin and not negatively impacting the performance of it. Creating the perfect infield soil is all science, period. The art is in maintaining it while dealing with all of the variables that weather, player preference and scheduling throw at you.
Dave Dwizlewski, consultant, Gail Materials, Corona, CA
Standard Specifications for Infield Mix: One of the most import points to recognize is that a standard methodology for testing needs to be established. As of now I prefer the ASTM F-1632 or ASTM D422 procedures for testing infield dirt. Standardizing the acceptable methodology is the only way to compare “apples to apples” when you are comparing infield mixes.
The basic infield mix for city parks, youth leagues, high schools and even some colleges should fall into the range of 70-75% sand with combined silt plus clay ranging from 25-30%. The silt to clay ratio should be in the range of .5-1.2. The fine gravel content should not exceed 2% and the distribution of sand particles should have the highest percentage in the medium particle size fraction. Since a 2 mm particle size is the maximum sand size (very course sand) it comes to reason that to achieve this particle size distribution, the parent material should be processed with a 2 mm mesh or smaller screen.
Gail Materials starts our screening process with 1.8 mm mesh screens. Many infield mixes are quite course and are often screened at ¼ inch or 1/8 inch. Screening to a texture of 2mm or finer is difficult especially in wet climates therefore in certain parts of the country it may not be feasible to produce infield mix in this manner. Be aware, however, that the wider the distribution of particles the more a soil will tend to consolidate. Courser particles are also abrasive. Higher end colleges or professional facilities tend to prefer a higher combined silt plus clay content in the range of 35-45%. With this type of mix the same rules apply for the silt to clay ratio and gravel and sand distribution.
Tips for Best Performance on Low Budgets: This is a tough one because if having a nice infield skin was easy then everyone would have them. The fact is that it’s a lot of work. I do not believe in “silver bullets” products that are sold as “no maintenance” or “reduced maintenance.” We try to educate the end user on Best Management Practices but we also try to manage expectations. We constantly are providing literature, holding work shop clinics and we even produced a free educational DVD on infield skin care. At some point the client has to except some responsibility. We find that cities or schools that value their baseball or softball programs put the time into taking care of the fields. You cannot have great fields without effort.
One management tool that can eliminate many issues is the simple step of tilling the infield skin before placing new material. All too often companies that offer infield skin care simply place new infield mix on top of hard dry skins without incorporating the old and new infield mixes. This causes a layering problem that can affect soil bonding, sheer strength and water movement. Tilling the existing skin is an extra step that is often skipped. All too often we have experienced this skipped step related to poor performance of the infield mix and the end user incurs extra cost to repair. If any contactor states it’s not necessary then that contractor doesn’t understand basic soil physics or they do not offer that service.
Questions to ask you supplier: In order to know if your supplier is educated about their materials then you need to put the time into being educated as well. If you don’t know then how can you tell if what you are being told is the truth? The tools are out there. I think anyone who puts in the time to learn just the basics about soil science and how it applies to infield mix may find out that many suppliers may not know about their materials all that well. Request updated soils tests and check for references, if this information cannot be provided, that should raise a red flag. Ask if the supplier screens their material or is it done for them at a local quarry. Companies that screen their own material tend to have better control on the quality. Also you can always ask for a sample.
James Hermann, CSFM, Total Control, Inc., field consultant
After 25 years working on infields I have come to the conclusion that there is no perfect infield mix. The perfect infield mix would be like the perfect soil. Talk to five different groundskeepers and you will get 10 different opinions on what works best. A safe playable infield is not the result of the products used; it is the result of how those products are used.
A quality infield mix is an infield mix that is consistently an accurate depiction of the professed sand, silt, clay ratios. Far too often suppliers will end a discussion on sand, silt, clay content with the phrase “plus or minus 10%.” In reality that makes the analysis worthless.
The more sand a mix contains, the more that infield will erode as the slope and the distance the water travels to exit the field increase. I would not recommend a sand content of more than 80% for a field with 1½% slope, especially if that slope initiated on one side of the infield and continued all the way to the other side of the field.
A skinned infield is more forgiving than a grass infield and can withstand a mix with more sand content since there is less perimeter turf area to be affected by lip buildup. The aggressiveness of the predominant level of play is also a consideration. A men’s softball field requires a mix with less sand and more stability than a children’s T-ball field.
I believe that before you can decide on the sand content of any infield mix you have to decide on whether or not you are going to be blending calcined clay with the mix. I look at it as “sand sized particles” not just sand. If a groundskeeper anticipates blending calcined clay with an infield mix, that mix should start out with less sand than a mix that will not ultimately be blended with calcined clay. When calcined clay is dry, it is going to react much like sand in a mix except for it is lighter and moves around more creating yet another consideration.
Far too often comparisons between products are made solely on sand, silt and clay ratios without consideration for the sieve analysis of the sand. A fine sand will react in an infield mix much like silt in that the mix will have the potential to be hard as a rock and dusty when dry and gooey when wet. If the field is located in a windy location prevailing winds will blow the fine sand into the turf perimeters adding to the accumulation of a lip.
In my perfect world, less than 20% of the sand would be in the “fine” range (.1-.25mm), at least 60% of the sand would be in the “medium” to “coarse” (.25-1mm) ranges and less than 20% of the sand would be in the “very coarse” (1mm-2mm) range. The mix would have a maximum of 4% or 5% gravel with no particles larger than 4mm.
Silt is a double edged sword. I prefer less than 8% silt at no more than a 1:2 ratio silt to clay on the fields that I work on because most if not all these fields rely on mother nature for all their moisture. Silt has the potential to make a mix dusty when too dry or gooey when too wet. At higher levels of maintenance, silt can aid in moisture management.
Clay: If I could specify one clayey (silt and clay) content that works on most of the fields most of the time I would say 20%. This percentage could vary either way by 5 or 6% depending on field usage, grading plan etc. This percentage could be lowered as much as 10 or 12% if calcined clay is anticipated as a significant portion of the mix 20% clayey content would not allow much more than 6% silt based on a 1:2 silt to clay ratio.
Tips: More problems are caused on infields by improper maintenance than by no maintenance at all. Low budget facilities rely far too heavily on roll up drag mats and not enough on a spring tine or nail drags. A heavy roll up drag uncontrollably moves far too much material, creates unnecessary compaction and brings more coarse material to the top. Every maintenance procedure should support positive surface drainage. More time should be spent on lip management procedures such as blowing or sweeping loose material off the grass.
I repair a few skinned infields each fall for a local municipality. Their crew uses a $30,000 utility vehicle and a $50 drag to manage their fields. They start at the edge of the infield and go round and round, working their way to the middle at about 30 mph and then start around the pitching rubber and do the same, working their way to the outside until the two patterns meet. These fields inevitably have a depression around the perimeter that resembles a moat when it rains. At the same time the pitching rubber looks like a little island encircled by water with a mound of material build up at the point where the two patterns ultimately meet.
Questions: I believe it is the responsibility of the infield manager to have the understanding necessary to make an educated decision on the infield mix he or she desires and require a sieve analysis from the supplier to insure a product that conforms to that need.
Bill Marbet and Glenn Lucas, Southern Athletic Fields, Inc.
Infield mixes are the foundation to which your field is built. Just the same as a foundation to a house, the infield mix that you chose will determine what kind of “house” you will have. When you speak to groundskeepers at various levels, from professional to high school to youth leagues, they will almost always speak of how their infield mix plays during the game, the management of the infield mix and what the players are saying about it. With various levels of play, there are various levels of expected quality to the infield mixes. We believe that the infield mix should be consistent and then can be amended to meet the groundskeepers’ needs and wants with field conditioners, topdressing materials and above all, the amount of moisture in the profile.
Standards are hard to determine, due to the regional materials that are presently available on the market. We will focus on what we expect infield mixes to be and how they relate to standard materials. Infield mixes should be in the following ranges of Sand/Silt/Clay, 60-70% sand, 15-25% Silt, 15-25% Clay. The silt to clay ratio can be .5-1, determined by dividing the clay % into silt %. Particle size of sand is as important as the silt to clay ratio. Ideally, your sand should be angular in nature and 60-70% of the sand, should be in the medium to coarse range. An infield mix that has a high percentage of fine to very fine sand should be avoided as it will become unstable. The infield mix must be professionally screened to be free of all debris. Also, you can request a current textural analysis of the infield mix that is being sold to you to evaluate the above information.
Infield mixes can be adjusted to different levels of play by changing the silt to clay ratio. Low budget fields, if they have a loose infield, can, over time add a heavier clay material to the field and create a firmer, safe and more playable surface and get the silt to clay ratio back to the .5 to 1 ratio. Another factor to look into when selecting infield mixes is moisture retention. Does the infield mix retain moisture? It might be overlooked in the process of infield mix selection, but, moisture retention is just as important as the silt to clay ratio. If an infield mix holds moisture, then more than likely, the silt to clay ratio is correct. If you have a lower ratio, it will hold less moisture, thus, not meeting the standards set forth.
What questions should be asked of the company providing the infield mixes? Can you provide me with a current textural analysis of your materials? What is the Silt to Clay Ratio, based upon textural analysis? What is your sand particle size and percentages of each size? Is the infield mix screened and if so, what is the screen size that it passes? What are the routine maintenance practices that are recommended for the infield mix provided? Can we get a different material based upon what our complex needs or wants?
Dena DiVincenzo, business development manager, Waupaca Sand & Solutions
Although there would be some positives to creating a single standard for infield mix, we don’t believe that a “one size fits all” standard would be practical. Preferences, local availability of raw materials, and maintenance practices vary by region. Standards are created locally. We advise using pair of infield mix “recommendations” based on water and maintenance availability. Our recommendations are derived from our knowledge and experience in the Midwest. We recognize that these recommendations may not be appropriate for other regions of the US.
Field Type #1: Limited or no access to water management tools. Limited maintenance capabilities. Recommendation: