After the crazy year that was 2020, as this year passes, everything is slowly coming back to normal. The major course update of the redesign of 17 is now fully complete and it looks like nothing was done - which is the sign of a great renovation!
The one big question that arose this year is "why are we aerating in August, when we didn't last year” so I figured that I would revisit the topic of why we need to aerate, why we were able to "skip it" in 2020 and why it needs to be done again this year.
As a background to why we need to aerate and to save some time, here are some links to older blog posts that hit on some different aspects of the topic.
- Link 1 How I maintain the greens at LedgeRock and why we need to aerate. We manage greens turf at the Rock differently than others but the proof that it is the correct way for the course is that the greens are fast and true all year, even through the heat of the summer, and do not need any extra maintenance to speed them up as they are already fast with just basic practices.
- Link 2 Timing - why timing is so important to the length it takes to heal.
- Link 3 How soil temperature affects recovery.
- Link 4 2020 ISTRC Test.
- Link 5 ISTRC Guidebook to Your Greens - everything you need to know about aeration.
- Link 6 A short video from the USGA Green Section explaining everything above in less detail.
The greens physical properties are tested twice a year. In doing so it shows how they are maturing and progressing, but more importantly, how the past aeration practices have worked. In the early years the turf needed more nutrients to mature and get used to its growing environments, its ability to withstand the rigors of play and the stress the weather creates. The downside to the extra growth was that the turf rooting was extremely dense and it essentially clogged up the sandy soil it grew in, reducing the infiltration capacity of the growing medium. The reduction in infiltration has a knock-on effect in the greens draining slower, a reduction in available air for the roots, more water logging - which in turn can increase compaction, increase disease incidence and encourage the encroachment of poa annua (which will in turn compound the issues....). The ultimate effect being soft greens, that are slow and do not handle stress well. Once the turf matured to a point where it could handle the stresses it was being put under, the fertility was able to be reduced and with it, the aeration practices were increased to improve the rootzone to return it closer to a new profile - but now one where the turf could really appreciate it.
The aggressive aeration practices over a couple of years brought them back to nearly new - almost too new in fact as they had virtually no organic matter in them to "glue" the soil together so they were softer than ideal. With a bit of tweaking, we found our ideal organic percentage and have been maintaining them to that since (We found the sweet spot to be ~1.9%OM near the surface). Having the buffer of a clean soil turned out to be the key to the light aeration done in August 2020 (which was necessary to get the Covid19 shortened season back on track). It was also a good test to see what would happen if we were to switch to a less aggressive aeration once a year. It went really well and the recovery was quick due to the tiny holes as only 1.5% of the surface was disturbed (vs the ~8% we aim for normally). The roots liked getting the air they get every August and the greens were perfect for the fall. However, the next round of testing showed that the infiltration rate had halved over the previous test, as well as an increase in that all important Organic Matter percentage (a soil can only drain as fast as its most limiting factor).
While the lower infiltration rate and higher OM percentages were still excellent by most standards, the gains of the previous years were quickly negated. One more similar aeration would only make them worse and detrimental to turf health and quality. We have worked hard to find the sweet spot to maintain the standards of the greens at LedgeRock so varying from the optimum numbers will reduce the playing conditions and eventually require more work to get them back to the expected conditions.
The spring 2021 aeration was pretty comparable to what was done the last few years and the greens were tested again in July so that we could see how well those practices worked. The results were not quite as expected! The infiltration rate had actually jumped to over 30" an hour - which is as good as, if not better than, a brand new green! This might imply that we don't need to aerate in August; however, it does not tell all of the story. The OM percentage did start to go back down from ~2.5% but it needs to get back to ~1.9% for optimum conditions. As mentioned above the limiting factor in drainage is the slowest draining medium and the greater the amount of OM, the less drainage there is, so ensuring that it is in LedgeRock's sweet spot is essential. The only way to do that is through core aerating (physically removing) and topdressing (diluting) the OM. While the August aeration will not be as aggressive as those in the past , it will be closer to a normal core aeration (rather than the the light aeration done in '20) to make sure that the OM percentage can get back to the optimum number.
So what about that infiltration rate? A week before pulling the cores to be tested we contracted Dryject to hydroject the greens - essentially using their machines without sand to just push water through the profile. The high pressure water creates non evasive deep aeration channels in the soil. When we did this, there was some grumbling that we messed up the greens but they were putting fine the next day and within three days they were back to 100%. This also helps dilute some of the OM in the soil by moving it deeper in the soil. This has the added benefit of removing the layer between the OM and the green sands which was one of the reasons the pocketed greens (2,4,10 & 17) struggled over the years even after the trees were removed and the fans added. The layer kept the water from moving through the profile properly so the surfaces stayed wet. Since we switched to using the Dryjects to hydroject the last few years those greens have been consistent with the others on the course. By loosening up the soil profile, it greatly increased the infiltration rate, albeit temporarily, but long enough to where it showed up on the report, giving somewhat of a false positive. Sometimes we get these eureka moments, where normally we wouldn't find hard evidence of what is happening other than the turf performing better. So while we now know this process increases the infiltration rates in the summer, helping the roots breathe better and keeping the profile drier for better playing conditions, it does not solve the issue of physically removing the OM like the core aeration does.
The timing of the aeration has also come into question this year. The ideal time to aerate is when the turf is actively growing so the heal time is minimized - unfortunately this coincides with the best time of year for golf..... Cool season turf only starts to grow when the soil temperatures are consistently above 55F. The soil temperature will obviously vary on the weather but also on the soil type. Sandy soils will heat up faster but will not retain heat so in the spring it takes a long time for them to warm up and they lose a lot of the heat they gain at night, whereas a soil will take longer to gain heat but will retain it, so it will slowly increase as it does not lose much on cooler spring nights. As such the fairways can be aerated earlier than the greens as they will reach that consistent 55+F quicker than the sand based greens. The L93 bentgrass on the greens also likes warmer temperatures before it really gets growing so that also adds to the slow recovery in the spring. The bentgrasses on the fairway are coarser older varieties but they start to come out of winter sooner than the L93, which also helps the fairways heal quicker. On a side note poa annua is a winter annual so it likes the cooler temperatures and will start to grow sooner - hence why poa greens (which are also usually soil based) green up and heal quicker in the spring. Due to our management practices the greens are virtually poa free. The switch to the earlier aeration date a few years ago did coincide with an increase of poa spots appearing on the greens. Luckily PoaCure finally became available and due to our testing we were able to acquire it on its release, which has removed the small bit of poa that was on the greens. Penn State is trialing another new poa control on the practice green and it is looking very good also. As part of that trial they actually measured the amount of poa on the green and it was less than 1% which shows that the maintenance practices are working really well. While having chemical controls to remove the poa are great tools, it is a much better practice to keep ensuring that the maintenance practices are directed to keep poa out so that the chemical controls can be used sparingly as a clean up so there is no resistance to them in the future.
Due to the golf schedule this year it was decided to go with an earlier aeration and see what would happen. While I was not happy about the date (due to the worry about recovery), it was nice to have it done and out of the way, especially in 2021 as we had the project on 17 fairway to complete also. At first it seemed like a great idea as an early spring warm spell had them growing and they recovered to about 80% in 10 days but then the temperatures dropped and with it the greens soil temperatures so the turf shut back down and they stayed at 80% until mid May - the time at which traditionally in this area the soil temperatures are consistently above 55F and the turf is happily growing. In 2020 no one noticed as the course was shut down due to Covid19 and with running minimal staff for safety reasons, the slow growth was welcomed as it reduced the work load!
The opposite happened on the fairways. Normally we would try and get them done early to get them out of the way and free up labor at the beginning of the season but also to take advantage of the extra healing time the warmer native soils afford. Due to some equipment issues and needing to contract out the spring aeration last minute, they were done later than usual so were not healed fully before the first onset of hot weather. All season they seemed to battle the heat and dry where they would recover with a few cool days and rain, only to open up again when it got hot and dry. We added some wetting agent applications to the normal program to help manage this better but going forward, it should not be much of an issue as the club purchased a new fairway aerator which affords us the ability to aerate when we want to in future years. We also changed our aeration practices a few years ago on fairways to "double" aerate in the spring by closing up the hole spacing. In doing so, it helps remove the desired organic matter percentage for the year, so there is no need to pull cores in August. Now we use solid tines in August which go a little deeper (aiding drainage) but have the added benefit of providing air to the roots but not beating up the turf with sweepers in the heat that are used to clean up the cores. The solid holes usually grow over within a week or so. Unfortunately due to the different requirements of the surface and therefore the maintenance of them, this schedule would not be ideal for greens.
At the time of writing, hurricane Fred is in the gulf and working its way north. If the timing is right and it makes it to PA, it should really help with getting the greens to heal quickly after aeration due to the warm temperatures and abundance of moisture. If it all goes to plan, the greens should be close to if not back to 100% by Labor Day. Going forward, we are planning on adjusting the golf schedule to better accommodate the aeration schedule in 2022. This will ensure that the healing time is minimized with minimum disruption to the enjoyment of the course.
As always, if anyone has any questions, email me at alan@ledgerockgolf.com
