RBiA grass and fast infield

The grass at the Ballpark is a dwarf bermuda, Tifway 419.  If any of you are golfers, you may have heard of it.  419 can be mowed down to less than 1/2" and still take wear well.  Most of the MLB fields have fescue/bluegrass turf, but they are also in the northeastern part of the country where it does not get as hot and the springs are much cooler.   It appears that the Ballpark grass is cut somewhere around 1" in height.  419  will develop a thatch layer that makes it spongy and does not allow water to permeate to the root bed.  419 for this reason has to be verticut anually to remove this thatch layer.  The RBiA appears to overseed the 419 with a fescue/rye grass to make the grass green for opening day as bermuda grass does not begin to flourish until the ground temps begin to warm after winter, in the 50's and 60's.  If this is not done, the field turf would be thin and not so green for opening day.  Doing this creates a problem to growing the grass longer than they do.  As the days get warmer, the fescue/rye grass begins to die out, but it has been shading the 419 since it began its spring growth in March.  You cannot kill the fescue/rye grass alone without killing the bermuda (419). So they keep the fescue/rye grass alive as long as possible, then as it gets warm, its cut allows the 419 to get sun, thus alowing it to choke out the fescue/rye grass with which the field was overseeded.  If the grass is left at a higher height, it will be ever increasingly difficult to transition to the 419 in the late spring, early summer as it will not get the sun it needs to grow. thenwhen it gets hot, the fescue/rye will die out and then you would have a sparse field which nobody wants.  I contacted Dr. Alan Nathan, Univ of Ilinois, who has a website on the physics of baseball.  Here is the email and his response.

Email:  Most MLB parks have bluegrass/fescue grasses and some have a variety of hybrid Bermuda grasses.  Hybrid Bermuda grasses can be thatchy if not verticut regularly, but I doubt that any grounds crew would allow their field to have that happen.  My question is whether or not the type of grass can affect a ground ball?  I realize the height can affect a slow roller, but is there any measurable difference that grasses can have? If a team allowed their hybrid Bermuda to become thatchy, would that have any effect?

Answer:  I am not an expert on different types of grass nor do I know of any careful studies of the effect of different grasses on a ground ball. But for sure there must be an effect.  Some infields in MLB are known as "slow", some are "fast".  Moreover, I would bet that any particular field is tailored to the type desired by the home team, so the groundskeepers know how to make it slow or fast.  However, I don't know any more other than that general statement.

 By the way, the effect is not likely to be as large as it is on a golf green, since a golf ball rolls on the surface whereas a baseball is mostly bouncing on the infield. Once it gets to the outfield, it can be rolling, so the effect there may be greater.

 

He does concede that baseball people talk about "fast" and "slow" infields.  This is due to several reasons.

1.  Fescue/Rye grass areas have softer turf.  The ground is not nearly as packed as it is in the southern part of the US having little to no clay in the soil.  Softer turf equals a ground ball losing some of its forward momentum when it strikes the ground.

2.  Fescue/rye grass in cooler climates can be left longer than the grasses used in the sourthern part of the US, thus haveing an affect although minimalt on the speed of the ground ball unless it is a bunt or it gets to the outfiled.

So, as the type of grass itselt making a difference in the speed of the infiled is minimal, how firm the turf is in the infiled has a much greater affect on the speed of the ground ball.  Hard ground and short grass equals a fast infield.  You cannot grow the cool climate grasses throughout the year in Texas and whether the RBiA groundscrew can soften the infield, I do not know.  Soil surveys of Tarrant county show the soil has a fair amount of clay which packs and is virtually impossible to make soft.  Topsoil would have to be brought in to soften of the soil.  Then you would have to take a large amount of soil out of the RBiA or raise the filed level.  Both costly.  So, what you have is Texas which gets hot in the summer, bermuda grass that does not get really growing until after the beginning of the season forcing you to keep the grass short, and firm ground which leaves you with a "fast" infield.  But that is basically the remedy for slowing down a ground ball hit in Arlington.  The Braves, Marlins, and D-backs will have the same basic infields, although they may use another bermuda hybrid.