Magazine - Straight Talking

5 Sep 2010 by leestrutt

As quoted by Stella -

"If a fairly coarse sand, or sand/soil mix that drains well, dominates your existing rootzone/upper profile, then moving to straight sand is unlikely to be suitable."

I find this lack of understanding of rootzone dynamics amazing!!! If you were to have this senario, i.e. a USGA rootzone, is she seriously saying not to use straight sand?? Surely the whole process about matching topdressing with existing rootzones is sourcing and a material type that helps the existing rootzone i.e. matching or improving particle size and distribution within the rootzone and keying this material in. If I had the above scenario (golf green scenario), I would still use straight sand but match the straight sand to my specification.

Again this is meant to be STRI ahead of the times???

5 Sep 2010 by chrismitchell

Lee, I think what Stella means is that a very free draining rootzone would be better of with the inclusion of some OM within the dressing to give some buffering to reduce leaching. I'm sure she will tell us.

Chris

You will never see a statue in honour of a committee.

5 Sep 2010 by aturnbull

Hi Stella

A good, basic article on sand dressings but, as you are only aware of I am sure, is that in our industry once you put your head above the parapet you are likely to get people trying to shoot it off. With my own experiences of being publicly shouted down I shall try to be gentle!

Over the past 20 years sand only dressings have been discouraged, especially by the STRI, but I have used only sand dressing due to two reasons:

1. cost
2. why would you want to add more organic matter into an environment that is producing more than is being broken down, ie thatch?

There is huge downside with pure sand. I have recently witnessed on-farm storage of veg crops using sand. The reason? - sand preserves organic matter. The idea of sand helping with air circulation so that microbes can breathe and break down thatch does not seem to stand up to scrutiny. What it does is produce a harder surface for better ball roll, but thatch is better removed physically through scarifying and coring.

What I have found to be best is to find the particle size in your rootzone that controls drainage, and to apply a sand dominated by that size. This increases the percentage of that sand and leads to increased surface drainage and rootzone aeration. Applying a coarse sand on top of finer sand only creates a perched water table until a sufficient dept of sand is built up for the water to be pushed through the layers underneath.

What, perhaps, we need to ask is 'do we actually need to dress as much as we do?' or is the answer because 'we've always done it this way' going to blind our thinking?

With a shared background in biology I would love to discuss this topic with you. I won't be at Saltex but will have a stand at ScotsTurf in November.

Best regards

Andy Turnbull

5 Sep 2010 by mackay

Course sand on top of fine sand will certainly not produce a perched water table.

I also don't agree that a sand as topdressing will inhibit thatch breakdown. Stella was advocating a little and often approach combined with keying in etc etc. , ie amelioration of the existing profile. Doing this will not create a 'sterile' environment free of detrivores, quite the opposite, and the comparrison between using sand to store root crops and sand as a topdressing in this manner is an utter nonesense.

5 Sep 2010 by aturnbull

Hi mackay

"Course sand on top of fine sand will certainly not produce a perched water table." - I'm afraid that the science and personal experience proves me right on that one.

Little and often sand dressing, of the right particle size related to the underlying material, can produce firm and fast running turf with good surface drainage. I bow to your correction Sir.

What I am referring to is heavy dressings of sand unrelated to the actual rate of build up of organic matter. If too much sand of the wrong particle size is applied it will bury thatch and exclude air, hence the preserving of thatch - not 'utter nonsense', but fact learned from experience and study.

The way to prove this is to ash the organic matter and measure the carbon content. Sand top-dressed turf surfaces can show as much organic matter content as undressed surfaces. The organic matter is still there, just not in the form of a heavy mat but interspersed with sand particles.

Would love to have a chat about this with you. Email messages during debates may appear to be aggressive in tone when not implied. My number is 07900 692052.

Best regards

Andy Turnbull

5 Sep 2010 by mackay

Yes, messages can come across wrong can't they?!

Agree with heavy dressings of sand being dangerous, but this was not what Stella was advocating was it?

Not certain you have the definition of a perched water table right, though I'm prepared to accept I could be wrong on this point. Perched water table occurs when the infiltration rate of an underlying material exceeds that of the material above it and there is no blend of the two, not the other way round. At some point down the soil profile there will be insufficient hydraulic head in order to facilitate drainage and so the water will perch artificially above the lower better drainage layer and no further drainage will occur regardless of time. Can a free draining soil on top of a less well draining one be termed a 'perched water table' when the less well draining material underneath will still drain, however slowly?

Finally, I quite agree with you: sand of the right particle size (or wrong if you are a greenskeeper!) is an excellent preserver, but this is a very different material from the one we ought to be topdressing with, and particle sizes would not fit within the STRI's curve above. Therefore, not sure it's a correct analogy for the above discussion within the concept of what Stella was saying.

I will ring you later in year once I have more time on my hands as would be nice to have a chat. :)

Incidentally, not sure if it would really work on a top quality green that needs to be in constant play, but I've used 4mm screened pure sand rootzone to topdress cricket outfields in the past and this is much much cheaper than any topdressing - has anyone heard of any greenskeepers doing this?

6 Sep 2010 by chrismitchell

If enough coarse sand is applied over a long enough period the depth of free draining sand could have enough head to percolate through a much finer rootzone beneath it. Something like 100 metres with a heavy clay so a lot of sand woud be required! I never have seen the point of applying materials that are free draining above something that isn't. It just gives something for the water to sit in. It is more important to create a structured rootzone where OM cements together the particles of mineral material to form aggregates with cracks and fissures. In other words for a push up green a balanced dressing of correctly sized and shaped sand and soil. How many times do we hear in gardening books about using sharp sand to loosen up the soil. Sharp sand is very angular and makes wonderful bricks when mixed with clay and baked. As Stella says good mechanical mixing in of the dressing is vital but the dressing must be compatable with the rootzone. I have seen some horrible rootbreaks over the year where turf can be rolled up with the hands by using the wrong sized material.

Chris


P.S. Stella you've started something here!

You will never see a statue in honour of a committee.

12 Sep 2010 by Michael Rogers

I think a perched water table is water held in a layer above another layer of different granulometry. I would go on to say that some perched water tables are intentionally created and others are not.



Mackay is correct to say that USGA specs have the finest layer in the sand, then pea gravel if used and then gravel, descending in depth is increasing in particle size. Saturated hydraulic conductivity is one thing and unsaturated hydraulic conductivity is not for the weak of heart. Around six months ago or so I spent three days investigating unsaturated hydraulic conductivity and knew less at the outcome than in the first place.



The idea with a USGA spec is to calculate your D values for your sand, gravel and then decide if you need to put in the pea gravel and to see if the various layers are compatible.



The USGA perched water table holds water in the sand above the pea gravel and gravel or just gravel because there is more tensile stress in the sand than in the coarser layers below. A properly specified USGA mix will balance drainage with wilting.



If you have some horrible compacted clay layer, a prolonged rainfall will fill any medium whether coarse or fine above it. This is a perched water table by definition, if the sand being filled by rain is coarser than the medium below it so be it, the clay below it is the cause of the perched water table not the coarser sand above a finer rootzone. The cause is an impermeable layer, full stop.



Saludos Michael Rogers

30 Sep 2010 by Par for the course

As the main reason for using straight sand would appear to be purely financial, what is the true cost of going over to straight sand. Would I be right in thinking that the extra cultural procedures required (more frequent applications, more spiking and the like) will be carried out without cost. Also what is the cost of applying diatomaceous earth ceramics such as Profile, Axis or Isolite CG. This is on top of any extra irrigation and fertiliser applications that may be required. All I am trying to say is price and cost can be very different so do your sums before tampering with one of the fundamentals of good greenkeeping practice

8 Oct 2010 by aturnbull

Hi Par for the course

Financial reasons may be the catalyst for considering straight sand topdressing, but for me it was purely agronomical. I asked myself the question one day, "why do I put on more organic matter into an environment that already has an excess of organic matter, i.e. thatch?". I also cannot see why extra cultural practices are required for sand dressing.

It would be good to further this debate face to face. I have a stand at ScotsTurf next month (under the name of The Great Turf Company) and, if you can make it, let yourself be know and we will chat.

Best regards

Andy Turnbull

1 Nov 2010 by Jock Hyde

G'day to all of you,
very interesting reading, and all appropriate for an issue at our local golf club. The old sand v's soil debate!
I thinks that sometimes a separation occurs between golfers and greenkeepers / agronomists.
I personally feel that whether anyone agrees or not, the golfer must come first in terms of the demands and thereafter the measures to be put in place on the golf course.
If there are no golfers then there is no need for a golf course or staff. It is a hard balance to find of course, and lots of ways to skin this cat.
I would appreciate your opinions on a very simple question, if you have soil based greens with a fairly high clay content, say 30%, and the rest of the soil has a very fine particle size, and this results in greens and fringes that get wet in sumer with irrigation, and wet in winter with rain, will coring and sanding along with all of the other things that must happen in tandem improve the quality of the turf, and ultimately the performance as a golf course?
I know this sounds over simplified, and I do understand the various dynamics involved, but purely in terms of performance and playability, all other things being equal, is this the way to go.
Our greens are I noted above, very hard if no rain or irrigation, soft and fairly average to hit to or putt on apart from peak growth periods such as spring and early summer. Inconsistency would be the norm, even though from an aesthetic perspective they look pretty good, they are generally healthy other than suffering from some bad moss as a bi-product of poor drainage and P.H, and average soil fertility.
As you would expect opinions are mixed as to wether to proceed with the change, and of course finance will be a consideration, but, is this the way to go if you could, if you wanted to improve your greens and take them to the next level?
All comments greatly appreciated.
Regards Jock

2 Nov 2010 by gregevans

Hi Jock

You simplified it very well. On your high clay content, added with a fine rootzone, a pure sand that meets a U.S. specification grade sand is definately the way to go. The greens that you describe are very similar to a number of courses across the UK. Not enough moisture and they crust up and become impossible to hit too, but too much moisture and they turn in to puddings very quickly. A fortnightly light dressing will solve this issue inconjuction with heavy dressings at certain times of the year coupled with aeration.

One other consideration with a pure sand mix over sand/soil is most certainly the cost issue. You are paying a small fortune for that small quantity of OM. For the same yearly budget on dressings you could be putting out an extra 40% of dressings if you went with pure sand over sand/soil. In these times, needs considering.

Go straight sand. Applied in the correct manner you will definately go to the next level.

Good luck.

Greg

2 Nov 2010 by Jock Hyde

Thanks Greg,
this certainly confirms what I think without getting too complex about the various other components that cloud the issue. Ironically all of the issues that do or can evolve from the change over are already there anyway i.e. perched water table, which you already have its just that the water is on top or the first 2" instead of being moved down? Then drainage around the green on the fringes summer or winter, especially relevant with the increased irrigation. I have suggested that picking the low spots around the greens and using a large diameter auger to drill through the silty top soil, and then into the river metal beneath. Therafter backfilling with good drainage material and topping of with soil to create large soak holes.
I work with drainage all the time and find this work exceptionally well for exteremely large amounts of water, far more than would be applied daily to our greens. There is some resistance to this idea, more probably from those who would prefer to not to change the greens and keep the status quo. I believe this would work very well and is a cheap solution when you can't actuall channel the water to a drain as such?
Then there can be the increased disease pressure, but when you already have to spray and you are only improving the drainage, the minor increase in spraying requirements must be acceptable surely?
Feeding may have to be increased and therefore for us an extra mow a week, but hardly a major on 9 small greens?
The only area I can see some reasonable extra cost would be that to expediate the the exchange that coring twice a year as opposed to the once we do it would be required, and probably a better way to go from a soil structural integrity perspective. Better to go twice with 12mm hollow than once or twice with 25mm lets say?
slow release or organic liquid fertilizers could help the microbial activity and reduce the potential for excessive thatch build up and growth flushes?
More comments on these points are greatly appreciated.
Cheers

Jock

2 Nov 2010 by gregevans

Jock, I don't know what your thatch levels are like but if they are not too bad I wouldn't worry about hollow coring if your main objective is improving the drainage of your greens and the top layer playing surface. In fact if you are putting out enough sand you will be diluting the OM very quick anyway. If you Verti-drain frequently and deeply in the right conditions (not too wet) I feel this will give you the results you need.

On your disease point you are right in the short term you will increase the disease pressure. But in the bigger picture you are creating a porous profile that will reduce your disease pressure. You just have to get there first.

Regards

Greg

P.S. You are right on your auger theory.

2 Nov 2010 by Jock Hyde

Thanks Greg, I appreciate the time you've taken.
Cheers

Jock