Edgbaston- Rolling out our programme

David & John Lawrencein Tennis

As regular readers on the Pitchcare website forum, Edgbaston Priory Club's Grounds Management duo of Grounds Manager Dave Lawrence, and Assistant John Lawrence were inspired to write a piece related to a recent thread, in the hope of offering a full view of how they manage soil moisture when drying down courts ready for the playing season, and also their beliefs regarding the use of testing equipment, and how combined with the skill of good Groundsmanship, the quality of the surfaces we deliver can be improved

To give the piece some context, the thread which inspired this piece can be found here - under Cricket: Pre-season rolling.

Okay! So first we should address the elephant in the room. The thread which has inspired us to write this piece is on cricket, and we prepare tennis courts. However, in a lot of ways our surfaces are very similar. In fact, the percentage clay on our tennis courts isn't too far behind most test match venues. Our preparations should in theory mirror that of those carried out on a cricket table, apart from the final pitch prep when the cricket guys get the rollers on and drop the height of cut. So for this piece, the cricket guys may want to imagine our tennis courts are just a big cricket table!

One of the topics that has come up in the thread concerns 'bounce' and the usefulness of Clegg Hammer readings. We'll return to the Clegg Hammer later, but first, we should address how we create 'bounce' on our courts.

Figure 1- Our Garden, tearing in to the Centre Court surface to remove any thatch buildup.
To us, the initial part of this process starts the previous autumn with the renovation. Quite rightly, a number of posters brought up layering and how this can have a detrimental effect on ball bounce. This is why we feel renovation is so important! In brief, we scarify the courts heavily every winter, down to at least 10mm (we go further if it is required) using a Graden GBS1200. All debris is removed using rotary mowers and a power brush, to ensure that nothing is left in the surface. Any thatch layer in there is effectively going to act as a cushion the following season. For example, if you imagine putting a wooden board on top of a mattress, no matter how hard, or thick that wooden board is, the mattress will always absorb a huge amount of the force placed on the board by a ball bouncing. No amount of rolling is going to make this 'sponge' layer go away, whether it is a mattress under a wooden board, or a thatch layer underneath the topdressing we apply.

Away from mattresses and back to the courts; we keep scarifying until we are sure any thatch layer has been entirely removed - we'll take cores when we think we've got it all to make sure that is the case. We'll then aerate using solid tines, add any fertiliser or chemicals we feel we need, and then seed and dress the courts. Hopefully the grass grows well and we have complete coverage before the winter. However, the most important aspect of our renovation is to ensure the soil is clean and pure, making sure that there is no potential for layering to occur, either through poor amelioration when we work the new topdressing in, or by burying a that layer creating a break of organic matter which will never consolidate or ameliorate in to the profile.

Figure 2- Post renovation aeration being carried out on our practice courts.
Through the winter we'll continue to aerate at various depths. Now we're aware that according to Cranfield one aeration operation a year is sufficient for relieving compaction, and actually we don't argue with this theory. As with everything in Groundsmanship, we should always question the motive for doing something and, if it isn't necessary, we don't do it! However, we aerate through the winter at varying depths. This helps to create channels for the grass plant's roots to make their way down. Good rooting will in turn pull the soil profile together, preventing any of the layering we try so hard to avoid. This gives the profile strength and stability, and ultimately helps with ball bounce - be it a tennis ball on our courts, or a cricket ball on a wicket.

Another thing we've trialed in recent years has been the use of an Air2G2 air injector on the courts, normally in mid-October. Now we will add a slight cautionary note, by pointing out we've only done this behind baselines and around the court perimeters so far - not actually on the 'in play' areas of the courts. However, we have noted that the courts are staying drier through the winter, are rooting deeper, and are showing more wear resistance in season. We have heard concerns from other groundsman, suggesting that the operation may be too aggressive, and open up the base of the profile too much. However, we are yet to see any negatives from this operation, and don't feel we are likely too.

All being well, we won't aerate any later than mid-January, other than light sorrel rolling. This is to ensure that all holes are closed up before we start our spring work, so there is plenty of time for the surface to bind and heal before the courts start to be dried down for the playing season.

Much of the pre-season work is site specific, but ensuring the surface remains clean and free of any organic matter build up is a must. In addition, we treat for moss, and make sure this is brushed out before we start drying down. We've mentioned our mattress analogy already, so in this case, moss would be a mattress on top of the wooden board! No amount of rolling is going to shift it, so it has to go.

Figure 3- While pulling covers with limited staff numbers is hard work, it helps to facilitate our 'little and often' approach to drying down our courts.
For us, our dry down starts properly in the second or third week of April (a relative luxury compared to most cricket squares we accept!). There is plenty of 'light' rolling when we use the cylinder mowers, but nothing of any great weight before then.

At this point, we should explain how we approach our 'pre-season rolling' or as we view it, our 'pre-season drying.' In order to explain this properly, we need to explain our perspective on drying the courts down, and how rolling fits in to this.

For us, in order to create even bounce, we need to ensure that the whole profile is dried evenly, so that we retain some moisture content right through it. Now, in our view, a heavy roller is not always the best way to do this, as in our opinion quite often, particularly when the surface we're working on is in the early stages of 'drying down' we can pull too much moisture out of the surface too quickly. As a result, we do a lot of our 'rolling' with our Dennis FT610s, and also, our court covers. Ultimately, with a clay surface, if we look at it in very simple way, we're trying to bake the clay hard. If we pull all the moisture out in one go, the clay crumbles, and we lose stability. However, if we pull the moisture out slowly over time, until we hit the optimum level, the surface will have dried evenly through the profile, giving a firm-hard playing surface, and no crumbling.

Now, we aren't suggesting that our methods are accessible to everyone. We do a lot of our 'rolling' using our rain covers, which would certainly be prohibitive to virtually all cricket venues, but the principle is the same. We'll often pull the covers on overnight, even with no rain forecast. The pressure on the surface is much less than if we took a heavy roller on, but is enough to pull some moisture up through the profile. When the covers are removed the following morning the surface is then baked under the sun (hopefully!).

The problem, as we see it, is that if we roll the nuts out of a surface with as much weight and as frequency as possible, we're going to pull the moisture out to a certain depth and create a break. Once the profile has been dried too much, and that break has formed, no amount of irrigation is going to relieve the break, without aerating through it to allow to profile to re-ameliorate. If we do the dry down slowly, we can monitor the profile, without risking going too far and not being able to fix any problems we could create.

As with any venue, a lot of what we do is dependent on the weather. There have been years where the heavy roller has never made it on to our courts, because it simply hasn't been needed. We've had enough warm days where we've been able to bake the surface without the need for additional weight. That said, there have been years where we've needed to ballast up something bigger, because weather and, therefore, time has been against us, and we've needed to pull more moisture out of the surface quicker then we'd like in an ideal world.

Figure 4- Court testing in full swing
This though, is where we think testing equipment does have its place. We're not suggesting that Clegg Hammers, or moisture probes, should ever replace the experience, touch and feel of a well-qualified grounds professional. However, these tools can be used to confirm what we often suspect, and refine and fine tune our decision making. The other advantage for us, is that we can seek some level of consistency and uniformity in what we are doing, not just from one court to another on site, but even from one venue to another.

As a pre-Wimbledon event, we try and produce courts which match their playing characteristics. By knowing what they aim for on a Clegg Hammer reading, we can aim for a similar court hardness and, therefore, speed and bounce.

The Clegg Hammer and moisture meter, for our venue in particular, are invaluable pieces of equipment, and detect variations with far greater accuracy then we could by touch and feel. In some ways, this is where the level of play for which you are preparing your surface may decide whether these implements are worthwhile or not, as the variations in moisture for us may only effect the bounce of a ball on a forehand by, say 5-10cm. To the average club player, probably not a noticeable amount, but to players from the world's top 10, that is a huge margin.

Figure 5- How a grass court should be constructed- ours don't even come close!
As a result, we test the courts morning and night during the playing season, on at least fifteen pre-determined points on each court, so that we can monitor consistency, and address as necessary. For example, if an area has become too hard compared to the rest of the courts on the Clegg Hammer, we can confirm the problem is that it is too dry by checking the moisture probe readings for that area, and then apply additional local irrigation to address the problem.

This is where the tools are invaluable to us. Anyone familiar with our site and our construction will know the issues we face with inconsistency. Our three practice courts are constructed on native soil, and so are significantly effected by the water table. Our block of four match courts and centre court were recently reconstructed (2012/13), but not in a way that we would have wanted, had we been working at the club at the time! We have sub soil where there should be top soil, road stone and gravel all over the place, and even the depths of each vary across individual courts, never mind from one to another!

On a perfect construction, the only allowance you would likely need to make when drying down would be for shading at the south end, however for us, our courts don't dry consistently because of the issues underneath the grass. Being able to test the surface hardness and moisture levels on a very local level allows us to make adaptations to our maintenance, that from feel alone, we'd struggle to refine to the level required. Now there is no arguing that this isn't currently working for us. The courts have been acknowledged as being amongst the best in the world by players, governing bodies and sponsors, so there must be something in what we are doing!

Figure 6- A tweet from June 2015.
We genuinely believe that a lot of our success has been down to how we have managed soil moisture in relation to drying down / 'rolling'. We put out a tweet last year (via our twitter account @epcgroundsteam) which alluded to this, even if it didn't quite blatantly say it! That moisture through the profile, when consistent, literally does act like glue, in that it holds the soil together. It doesn't matter whether it is the expensive stuff on centre court that has been imported and should bind every time, or the native stuff on our practice courts that is far from ideal - if it is too dry, it will not hold together. It's also important to get the roots down as deep as possible, to hold the profile together and prevent layering, hence our belief in the benefits of Primo Maxx (though we won't open that can of worms right now!).

So to summarise:
• The thatch has got to go - leaving it in is like laying a sprung floor!

• Root depth is vital, and encouraging it should not be underestimated. Dense, deep roots hold our profile together and contribute to giving a 'hard' surface!

• Don't let things dry too much. Consistency through the profile is the key - if it's too dry, the soil will be unstable, and will absorb bounce - if it's too wet, it will do the same thing. Finding the optimum level is the key.

• Every surface is different, whether it's our centre court compared to our practice courts, or high quality county standard pitches compared to the local village square. Everywhere will have variations and everyone's optimums will be different. The important thing is finding these optimums and, in turn, comes the consistency!

So to three final points. The first regarding testing equipment itself. We use a Clegg Hammer, which we know (at the best part of £2,000) is out of reach of most venues budgets. However, there are alternatives. For example, whilst attending the All England Club Groundsman's Seminar, we were shown some of the ways they measure ball bounce. The Clegg Hammer is in their arsenal, but they also record ball rebound percentages. The method for this is to drop the ball which would be used for play at a height of two metres, recording the rebound height, and then converting it to a percentage. The test equipment consisted of a washing line pole with a tennis ball tube taped to the top and a bit of string to release the ball, with a tape measure on the side of the pole so the user could see the height. We suspect a piece of home-made kit like this would be far more accessible to most venues, but still gives you some valuable information. After all, if it's good enough for Wimbledon!

Figure 7- Despite the challenges our venue presents, we still manage to produce world class playing surfaces.
Our second point; we've been to other venues and passed on our observations and ideas regarding rolling and drying down. Those that have implemented even a small part of what we've discussed have seen improvements. We're always more than happy for people to come and have a look at how we do things, and we're also happy to come and offer our opinions when time allows. Whilst we work at a private members' club, we have a severely restrictive budget to work with; in fact, in our previous roles with a local authority we had more money to spend! We have looked at times at some of the kit that's available that others have managed to purchase, but instead of looking on enviously we have adapted with what we can afford and, judging by the results we have had, we've found we are getting results that both ourselves and the players are happy with! We can adapt and there are ways around these challenges if you're brave, try new things and are open minded to innovation.

Our final point to finish is that, whilst we believe in what we are doing now, there's every chance that, in twenty years' time, we'll be doing something completely different. Everything we do in this industry is progressive, no two years are the same, and so being able to adapt is hugely important. We fully expect people to shoot down our views and offer alternative theories as to what is leading to the quality of the courts we're currently producing. And honestly, if someone has a better idea, which is more plausible, we'd listen, because it is the best way to learn!