Massive Increase in putting green OM levels. Now what?

For the past 3 years the organic material in the top 2 cm of our greens has seen a steady increase. I discussed in a recent post about the value of time series comparisons for fertilizer recommendations and I think the same is true for organic matter management. Would you say we are doing a good job managing our surface organic material levels?

I don't know about you, but for me, we are not doing enough and the data is clear. Regardless of the conditions of the greens today (they are pretty damn good BTW) the upward trend will likely change the way they perform in the future so I am more comfortable with a trend line that is flat or unchanged year to year.

I've always found aerification a bit confusing and never felt like I had the tools to make a good decision. I was essentially guessing which didn't make me feel good when the guess resulted in massive disruption to our playing surfaces. Was it justified? How could I be sure? I started measuring the Total Organic Material by depth in my greens 3 years ago. We take samples at depths of 0-2cm, 2-4cm and 4-6 cm and this shows us where the organic material is located and how it is changing over time.

The charts below illustrate all 3 depths over the past 3 years.

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We see that in the top 2 cm we have an upward trend that is much higher than the average amount found in greens with a similar turf species composition.

In the 2-4cm depth we have relatively constant OM levels that are only slightly above average.

From 4-6cm we have constant values that are almost exactly average.

Firstly, it's amazing how much less OM there is even when you go slightly down in depth. This does make sense as most of the plant material is found at the surface. Sure, we have roots down deep, but the vast majority of them are found in the top 2cm. This data shows that quite clearly.

While it might be natural to panic at the sight of the increasing trend in surface OM levels, it is important to take actual conditions into account first. Essentially, the greens are the best I have seen them in the past 4 years. The turf is healthy and I can produce good playing conditions for more days than I have ever been able to in the past. The only problem is that when it rains heavily, they puddle slightly. There is no need to panic, I can anticipate future issues but today the greens are doing just fine.

Slight puddling on Jan 12, 2023 after 28 mm of rainfall.

So why have the organic matter levels in the top 2cm being going up so rapidly? There are many things that can impact the OM levels in the soil and probably all of them are at play here.

1. Not enough sand: I had a suspicion that our sand had too many fines so stopped applying it until I found a better sand source in 2022.
2. Higher growth rates: Chicken and the egg situation here. Are my best greens the best because of their higher organic matter levels or are the organic matter levels higher because of the better growing conditions on my best greens. I think it's probably the later situation here but despite the higher OM levels, these greens are my best.

Either way, I now know where the organic matter is located and know that I need to do more than I was doing in the past to slow the upward trend of Organic material in the top 2 cm of my rootzone. With a time series by depth and good sand application recorded this makes it very easy for me to make a decision on how much sand I need to apply in 2023.

So I wonder if the slightly poor drainage is a result of the higher OM levels or is it due to the poor sand quality? I decided to test that out as well this year. After the OM was burned off and measured, the sand was put through a sieve to analyze the particle size distribution of those samples. The results below show that we do in fact have some of the "highest amount of fines" of the 7 or 8 courses that have been tested this way so far. FFFFFFFFFFFFFFFF

www.asianturfgrass.com

I actually already knew this and this is why I stopped applying the sand from our local suppliers. They had too many fines and I was able to test this in my own office lab. I test all our aggregates to ensure that they meet the specification we are paying to receive.

Fine Gravel: We are at the lower end of the USGA spec recommendations with a slight increase as you go deeper. This makes sense because the original rooztone likely had more coarse material as most of this material is removed when we topdress with finer sand.

Very Coarse Sand: Again, we are at the low range for this particle size with more located as you go deeper.

Coarse and Medium Sand: This is the meat and potatoes of your rootzone with the USGA calling for 60-100% of the sand to fall within this size range. We are below the recommendation but there is an improvement in the surface layer. This is likely from our most recent topdressing using properly spec'd sand from a far away land (hella expensive). The sand we are now applying is almost entirely composed of sand that falls within this size range.

Fine Sand: We have too much fine sand which is what I already knew. At the surface we have less fine sand which is likely from a recent topdressing using properly spec'd sand from a far away land.

Very Find Sand: We are WAAAAY above the recommendation. 3x higher actually. @#%^&*$%

Are we doomed? Do we need to rebuild our greens?

I think the answer is no. The greens today are actually just fine except for some puddling when it rains hard. So this suggests to me that the USGA specs are wrong or at least they aren't necessary for good grass.

Could our playing surfaces be better if we were closer to the spec? I think so.

The bottom line here is that today the greens are ok. If we continue to add fine material to the greens they might get worse. By adding properly spec'd sand in the future their conditions will likely improve. By continuing to measure the sand particle distribution by depth over time, we will be able to see if we are moving closer, or further from the USGA spec and will be able to adjust how much sand and to what depth we apply it at each year. If I do not see positive change in the next 3 years we will look at options to remove the fine material through coring or other more disruptive processes. 

Knowledge is power! For the first time in my 22 year career I feel like I have a good grasp of what needs to be done to keep our greens performing well without causing unnecessary disruption to play.

The plan for 2023 is this;

• Apply more sand than I did in 2022. This will be 2 aerification events instead of 1 using 18mm solid tines to a depth of at least 6cm. This is both to dilute surface OM but also dilute the fines deeper down.
• Use the correct spec sand even though it costs double.
• Be aware of our cleanup procedures post aerification to ensure we aren't removing beneficial sand particle sizes (coarser) from our greens. If the sand is wet and be blow them, the fines will stick to the surface while the coarse material will be removed.
• Check again next year to see what has changed.

That's it. It doesn't sound that impressive but without the data you cannot be sure that what you are doing is sufficient or justified. It also helps me make decisions that might actually improve our situation instead of doing nothing or making things worse.

Do I need to go deeper? I don't think we do because I have been doing lots of manual drill and fill on some of our low spots that are prone to puddling. I have tested the soil that I remove and it fits the spec nicely. The original rootzone mix is actually pretty good, it's just the topdressing over the past 20 years that was the problem. We only need to dilute the fines in the top 10cm where this topdressing material has been applied which is totally achievable.