Turfenomics: Productivity Part 4 Mower Efficiency and How to Cut Your Cost of Mowing in Half

How much grass can your mower cut? The most basic way of calculating this is to take the width of the mower and multiply it by the speed. Let's say our mower is 2 meters wide and can mow at 10 km/h (keeping the match simple here). In one hour it will have cut 20,000 square meters or 2 ha. Wow, that's a lot of grass. Unfortunately it's not that simple. A lot of things go into how much grass you can cut and any observant turf manager will know that the actual productivity of a mower will be much lower than the maximum theoretical productivity as calculated above. This post will discuss what influences mower productivity and strategies we can use to maximize how much grass we can cut with a given mower or resource input.

So why isn't our actual mower productivity the same as the maximum theoretical productivity? A lot of "mowing" isn't actually mowing. We use an hour meter to calculate how many hours the mower is operational and during this operational period the mower is doing things like warming the engine up at the start of the day, driving to the area to be cut, turning the mower, waiting for golfers, returning to the shop, and cooling the machine down before you turn the engine off. All of these mentioned things are time on the hour meter that are not cutting grass! Over the last few years of closely measuring mower productivity I have found that you will probably get anywhere from 10% (tees) to 40% (fairways) of the maximum theoretical productivity of a given mower. That means that you are only actually cutting grass 10-40% of the time that a mower is operational. What a waste!

Mower efficiency

There are also things that impact productivity while cutting grass. Things like how fast the mower is set to mow, mower overlap between passes,  and obstacles that cause the mower to have to reduce speed or turn to avoid. At my previous course we have very bumpy fairways and it took twice as long to cut 1ha as it does at my new course which has much smoother fairways.

A lot of what superintendents talk about is mower routing to increase efficiency. This is making sure that the mower isn't backtracking or transporting for longer than necessary distances. This is a great place to start but in the grand scheme of things isn't a major factor in mower productivity from what I have seen. Obviously this needs to be taken into account and mowers shouldn't be driving back and forth between holes over long distances. A classic example of this strategy going wrong was at my last course the operator would avoid golfers at all costs to avoid having to wait or disturb their round of golf. The result was a substantial amount of time spent driving from hole to hole to avoid golfers. It was much more productive to just stick to the hole that you were on before going to another hole.

Mowing pattern also has a huge impact on productivity because some mowing patterns require more mower turning which impacts productivity. The more turns that are required the more time will be spent not mowing on a given area. Let's look at my first fairway. It's a 510 yard par 5 with a long narrow fairway. The fairway portion of the hole is 375 meters long and the fairway averages about 30 meters wide. I'm using meters here because my mower productivity is measured in meters and ha.

Lets again take our 2 meter wide mower. This mower is sort of small for fairways but it's easy for math. The first fairway is almost 1 ha exactly. With our 2 meter wide mower going 10km/hr we will spend about half an hour mowing this fairway assuming no turns or waiting for golfers and we are able the mow flat out without slowing. Unfortunately we have to turn the mower because our mower isn't the perfect width of the fairway and we will have to do multiple passes to cut the fairway. Every time the mower has to make a 180 degree turn while striping it adds 8 seconds to the mowing time of the fairway. The worst case scenario for mower turns would be mowing the fairway side to side at 90 degrees to the line of play. At 375 meters long with a 2 meter wide mower that gives us 188 turns assuming no overlap. 188 turns multiplied by 8 seconds per turn gives us 1504 seconds or 25 minutes spent turning for a total mow time of 55 minutes. The other extreme is to mow the fairway lengthwise. At 30 meters wide we need to do 15 passes assuming no overlap. This will take us 120 seconds or 2 minutes to turn the mower (assuming stripes) for a total mow time of 32 minutes. In this case, mowing direction can influence our productivity by 42% or more! We can spend almost double the amount of time cutting a given area. Of course there are reasons that might justify this added expense but it's worth knowing what decisions like mowing pattern have on productivity. 

The real world these inefficiencies are even worse because of overlap. Let's say we have 20cm of overlap (10% of mower width) per pass. 20 cm x 15 passes is 300 cm or 3 meters. This adds 1.5 more passes to the job or a total job time of 32.2 minutes cutting lengthwise. Cutting from side to side we now have to make 208 turns which takes us 58 minutes to cut the entire fairway. This leaves us with an productivity loss of 55%! Over half as much grass cut per hour! It get's worse because with these mowing patterns you also have to do a cleanup pass around the perimeter of the cutting area! You are now cutting this area twice where this area is simply included in the regular mowing of the hole on half and half mowing. Of course we probably won't cut this way every time and if you do striping the productivity loss will probably be somewhere between the two mowing patterns.

If you cut half and half patterns you might not have to stop mowing to turn the mower. You can do wide turns while mowing grass at a slightly slower speed but you will still be cutting grass. This is where you will achieve the maximum actual productivity when it comes to mowing patterns. Actually, this isn't quite true. The maximum mowing efficiency comes if you never turn the mower like they do at Augusta National. The only catch is you need 22 $80,000 fairway mowers to pull it off. So the next time someone says Augusta isn't efficient I would disagree. They mow the fairways in the most efficient manner possible!

Ok cool. We all know mowing pattern impacts productivity but what about disruptions like waiting for golfers? Everyone knows this impacts productivity but it's hard to actually test it out. This spring I had an amazing opportunity to test this out as we were closed to golfers for an entire month in April due to Covid19. I had productivity data before the closure and productivity data during the closure.

Before the closure we were getting about 0.9 ha/hr on our fairway mowers. During the closure this jumped to 1.5 ha/hr even with a rooking operator (our GM). Once we opened back up this dropped down to 1.3 ha/hr. With golfers our average productivity was 1.1 ha and without it was 1.5 ha/hr. This is an increase of 27%. I've heard the 30% figure thrown around often and I was able to measure this in reality. The productivity gain was more in other areas such as tees and greens as we removed obstructions like flags and tee markers. On tees productivity jumped 200% because half the time spent "cutting" tees is spent moving markers. 

I don't know about you, but a 30% increase in productivity is massive. Combine this with the mowing pattern efficiency gains and you might be able to cut twice as much grass per hour. Double you productivity! Again, this is exactly what we did. After we opened back up we doubled the amount of grass we were able to cut or halved the amount of labor or equipment we needed to get the grass cut efficiently. Mowing is our most expensive maintenance practice so we stand to save the most if we can find ways to reduce the amount of mowing that is required.

How did we do this even when golfers returned? We prioritized productivity over all else. We cut as much grass as possible with the biggest and fastest mowers. This meant our fairway mower would now also cut approaches, some collars and some of the big tee boxes. Our big rough mower cut all the rough, and our small rough mower was no longer needed. There was no change on greens other than restricting start times and starting earlier to ensure that golfers would never catch our greens mower. 

We also avoided golfers at all cost with fairways and rough. We were easily able to cut half the fairways ahead of the golfers each morning. 9 holes takes us about 5 hours (total job time not just mow time). We start mowing at 5 am and the first group was off at 7 am. The first groups golfed pretty quick in about 3 hours. This had them finishing their round around 10 am or exactly when we were finishing mowing the 9 holes. The fairway mower was cutting every day without any golfer interference. Any time we were able to cut quicker, we would add more work to the fairway mowing job to ensure that it would be out mowing grass at a high productivity (it's our most productive mower) level for the most amount of time each day. This meant that we made some fairways bigger and cut more areas with the fairway mower as previously mentioned.

We had to change the mower routing to make this work because we used to mow fairways in blocks. One day we would cut the front nine and the other day we would cut the back nine. This practice maximized routing efficiency but sacrificed mower productivity in a big way. If we mowed fairways this way and started at 5 am, golfers would catch us about 70% of the way through the front nine days resulting in us having to mow the last 30% at potentially a 50% loss which would add about 15-20% to our total mow time and disrupt the golfers. This was made slightly worse because we would have to wait more often with our half and half mowing pattern as we would come across golfers on the green, tee and fairway that we would potentially have to wait for. To avoid this we could stripe but this would result in an inconsistent look and add time spent turning. Instead we would skip holes and cut half of the area each day. Notice I didn't say we would cut half of the holes each day. As each hole is a different size, we broke the mowing days down by area instead of hole numbers to evenly spread the work. With a slightly less efficient mower routing we were able to mow at maximum productivity all the time.

Rough was a bit trickier. We have more rough than we can cut in 2 days. We could have cut rough over 3 days but we didn't have the staff to pull this off. Instead we broke down the rough area on each hole and allowed a proportional amount of time for each hole to be cut at maximum productivity. This means that we would leave a hole without cutting all the rough on it! Instead of getting 2 or 3 hours of high productivity mowing on rough each day we now got 5 hours every day. This allowed us to get almost all the grass inside the cart path or close to the centerline of the hole. We would then go back and get the other stuff during golfer play. While it was slightly less productive, we were waiting less because these areas were far from the centerline and we could mow without stopping even when golfers were present. This allowed us to cut twice as much grass with a single mower and operator than we did in the past. We actually cut more grass than in previous years but with half the machine time and labor. A savings of over 600 hours on each.

Below is the tool I developed to help rough mower operators know how much time they had per hole. 

Now you'll notice that a tool like this doesn't maximize production (total amount of grass we can cut) directly. It indirectly maximizes production by keeping the mowers working in an environment that allows for maximum productivity without setting any production goals. Cut as much grass as you can in this amount of time. This reduces pressure on mower operators tremendously.

I also use a similar tool for when I do my favorite morning routing of rolling all greens, changing all holes and raking all bunkers. While I could simply brute force this job the most important thing is to get the greens rolled and the holes changed ahead of the first group of golfers. Raking bunkers is secondary and this allows me some flexibility to address factors that can influence my productivity like bad weather and working while wearing rain gear. While I can easily do this job before the 6 hour deadline when conditions are perfect, if the conditions are bad I cannot, so I need a way of gauging my progress and adjusting on the fly. We can always go back for the bunkers I miss or get anyone else who has an opportunity to help make up for my loss of productivity with lower productivity loss while golfers are on the course.

By assigning a time limit on each hole I can easily gauge my progress and adjust as I go. If we have 18 holes and 6 hours that leaves me 20 minutes per hole to drive there, roll the green, change the hole and rake as many bunkers as I can. Easy.

If we instead set a production goal instead of a productivity goal I would fail every time something negatively affected my productivity. Golfers would catch up to me on hole 15, I would be rushing and they would have to golf their last 3 holes on dewy, unrolled greens on yesterdays worn out pin locations.

I hesitate to post something like this because it can give a course a huge competitive advantage. Luckily for me no one reads this blog and people are too stuck in their ways to change. Joking aside, the lessons I learned this year will have a huge impact on the cost of our operations going forward and I hope they can help you too.

Genki 3 Way

A few posts back I talked about how I found it useful to compare a 30 day running average growth ratio to a 30 day running average nitrogen genki. This would tell me  how my grass was growing and how much nitrogen I had applied compared to the standard level which I have determined to be about 2/g nitrogen per square meter per month at a 100% growth potential.

After thinking and using that tool for a few months now, I wondered about the other nutrients. Last year I had issues with the grass not growing as expected and it turned out to be a phosphorus deficiency probably made worse by regular phosphite applications.

The growth ratio model showed that the grass was growing too slow and in reality it probably was as we suffered from issues caused by slow growing turf such as Anthracnose! The more experience I get with the growth ratio model, the more valuable it becomes as a tool to help me keep the growth rate where I want it and plant health issues to the minimum. Most issues I have had with the greens can be clearly seen when you look at how the grass is actually growing compared to how it should be growing.

I had soil tests and thought I had applied sufficient fertilizer but what I think may have happened was that as the roots shortened in the summer heat, the phosphorus in the surface layers of the soil were used up. The deeper rooted bentgrass was healthy and happy but the predominantly poa surfaces were suffering until phosphorus was applied.

This got me thinking about what it would look like to include a genki level for phosphorus and potassium as well. We know that potassium in cool season turfgrass is found at a ratio of about 0.5 compared to nitrogen and phosphorus is around 0.13. With this I can compare my applications to the standard amount. 

If the nitrogen genki is above 1 but growth is lower than expected, I can look to see where the other macronutrients are in respect to their standard amount. If growth is higher than expected I can stop applying nutrients altogether until the growth ratio returns to where I want it to be.

I currently look at 30 day running averages for everything but think that an annual running average might be appropriate for something like phosphorus which is used in a much smaller quantity than the other macros and is relatively immobile in the soil.

There are times when soil nutrient status won't impact growth rates and this is when either moisture or frost come into play. Without sufficient moisture grass won't grow and when there's frost, we don't get much growth either.

I wonder if something like this could replace soil testing for the high use macronutrient content in the soil? Soil testing provides a general snapshot but this provides an up the the day idea of how the grass is growing and how my macronutrient applications might be affecting the growth rates.

It could also potentially provide a more precise tool for managing bentgrass vs poa annua too. In my experience, the deeper rooted bentgrass has more access to nutrients and has always had a much higher growth rate than the poa. I hypothesize it my last post that it seems that fertilizer applications might be the best way to manage bentgrass over poa and this might be another tool that I can use.

As bentgrass populations rise the growth rates on those greens tends to go up. Again, this is probably due to the deeper roots having access to more nutrients in the soil and the tendency of bentgrass to grow more for a given amount of nutrient inputs. These two things combine to leave the greens with more bentgrass growing much quicker than those with mostly poa annua. Micah Woods hypothesized that the most sustainable grass might be the one with the highest growth rate for a given amount of inputs. I  agree.

As more and more bentgrass populates the putting greens I eventually need to start managing for bentgrass and not poa annua. Currently I need to keep both species happy so avoid a loss of turf quality. It's a fine balance and maybe this tool can help me do better with less guesswork. The practicality of managing greens to that extreme might prove to be a bit too ambitious but without the data you can't even begin to dream about doing anything like this.

Let's forget about that for a minute and look at the issues I had with growth in 2019 and how the genki level for the big 3 macronutients looked. For those sharp data people out there a few issues become glaringly obvious with models like this especially in the months with little to no growth. A light fertilizer application can throw that ratio wildly high as the ideal amount is close to zero and the closer to zero the ideal amount of fertilizer is, the more any amount of fertilizer applied will throw the model off towards infinite. You can see this impact on the chart below. Everything has this curved shape to it. This is kind of the reverse of the growth potential curve for my climate. Anyway.

Holy Shit! When you're not used to looking at something like this is looks like a rat's nest! That's ok and we will filter out some of the data to look at it individually. I've filtered the dates for the growing part of the season. You can still see how high some of the genki levels will go in the shoulder season.

It might look super inconsistent like this and it is! It will be interesting to see how increased awareness will impact my fertilizer applications going forward. Also if you want to criticize me, first show me your macronutrient and growth ratio chart. It might look like I have no clue what I'm doing and to be honest I really don't. The deeper you look into fertilizer use the more you will realize how much guesswork is involved. I'm just trying to reduce that guesswork.

The thick dark blue line is the growth ratio and as you can see, the growth rates in 2019 were less than I wanted them to be. Greens were fast but also anthracnose!

Here's the same chart but just with the N Genki 30 day and Growth ratio.

In the spring we were recovering a few greens that died due to civitas applications too late into the winter. Don't apply civitas in the winter unless it's warm and sunny.

The growth ratio was pretty good until June when growth rates typically pick up. As soon as the heat arrived, the turf growth didn't keep up to expectations. It's important to remember that this is a growth ratio, it isn't total yield. The growth rate stayed rather constant or slightly down but it should have been much higher. 

I've seen this before with nutrient deficiency issues. A neighboring course had growth stall after spring aerification and the more nitrogen they applied the worse things got. As they tried to increase growth (and the weather warmed up) they also increased the demand for the other soil nutrients and thus made the deficiency worse. It turned out that they were low in calcium and a week after a calcium application the greens were as good as ever despite what some people said (2 weeks to live my ass). This is exactly what happened to us last year. As soon as the demand for nutrients went up, the deficiency got worse. The total yield and growth ratio for June was much lower than we wanted and we paid the price.

For the entire year we were applying much more nitrogen than we needed to try and drive growth rates when in reality we were probably making things worse.

Now let's look at K Genki. 

For the most part, the K genki is high all year long. In August when the anthracnose started to get bad I started applying higher N and K as this is recommended in most of the literature. In reality these nutrients only have an impact on anthracnose if they are deficient. They weren't deficient. I haven't read anywhere that low phosphorus can make anthracnose worse. In reality I don't think it matters. To someone that measures growth like I do it's not about any nutrient in particular, it's about growth plain and simple. If the grass is growing at an adequate rate it probably won't have many issues. If your grass is growing too slow and it's poa annua, watch out!

Now, let's look at the P genki below. I've also included a weekly running average growth ratio to see the impacts of P on the growth rate in more detail.

Again, crazy high genki in the shoulder seasons. Ignore that probably.

For most of the season the genki level for P was zero. I wasn't applying much P because my soil test showed that I had enough. The issue I think was with the soil testing depth. The depth was down to 10cm but the roots at this time were barely 5cm due to a hot dry summer and poa being the shitty grass that it is. The roots issue probably compounded itself because the growth rates were too low. Low shoot growth rate and probably a low root growth rate too.

Mid August I applied a bit of P. You can see a big jump in the 7 day growth ratio. I could also tell a big difference in the turf appearance but the growth ratio started declining again. Another P app in early September and BAM, another big jump in the growth ratio. After that the ratio's trend towards infinity but it was safe to say I have finally figured it out.

I was also having trouble determining how much P was enough. With the genki P you can easily see how much is enough. That first application I made in August was only 25% of the monthly P requirements. Once I applied more than a month's worth we finally saw good sustained growth.

The growth tapers off through October but this is due to other factors like raising the height of cut and less frequent mowing after aerification etc.

You also notice that the genki goes up even after application dates and this is because the nutrient demands are decreasing each day as it gets cooler so what was a month's amount of fertilizer in early October, is a year's worth of fertilizer at the end of October. I don't know enough about modeling to fix these issues yet. Maybe one day I'll learn and improve this.

Fast forward to 2020.

Here's the N genki and monthly growth ratio.

Right away you can see that the growth ratio is much better if a little high. I wasn't going to risk things this year and I wasn't sure how all this really worked so I was playing it safe.

In the spring the N genki and growth ratio closely mirror each other. On an adequately fertilized turfgrass soil N generally is the limiting nutrient so you can see that seems to be the case for the Spring of 2020.

When we get into August the typical mineralization event occurs which releases nutrients from the soil organic matter. This is something I've observed over many years at my last golf course property. I was relieved to see it again this year. N genki has remained low this year as we have had more than sufficient growth.

This shows me that if you growth ratio is low and N genki is high, you need to look elsewhere for the cause of the low growth assuming you aren't using crazy growth regulators or lack of water to slow growth. I do use Primo Maxx on a 200 GDD interval and this is worked into the growth model I have made.

What about the K genki?

I was going to make damn sure that K wasn't the limiting nutrient this year as can be seen above. I wasn't using this tool until early October 2020 so I wasn't aware of how my K applications looked compared to growth.

In September you notice that the K genki and growth ratio seem to be similar. The N genki was around 0.5 at this time but K was even lower. Eventually the growth ratio went down but started trending upward after a mid September K application. As we were getting great growth due to mineralization I assume there was more than enough free nitrogen in the soil. Perhaps K was starting to become a limiting nutrient here because there may have been a growth response. K is relatively free in the soil and is used in relatively high quantities. We were removing lots of nutrients from clippings in August and any K that was mineralized may have been lost or something. There's no way to know this for sure but I can speculate.

Now that growth is slowing for the Fall, you can see the K genki trend upward.

Let's look at the P genki

I am definitely overcompensating here! Again, I wasn't acutely aware of this relationship until early October 2020 so I was being careful. Applying way more than is needed is easy with nutrients like P which are used at a rate of only about 13% of the amount of nitrogen. It really doesn't take much. I don't see any relationship with growth and P this year as it should be! If all nutrients genki levels are above 1, I don't think you should see a growth ratio below 1 assuming that there aren't other factors like moisture restriction or growth regulators or frost etc.

Again, trending upward now that growth and nutrient demand is decreasing.

Now that I have this tool I can use it to manage nutrients with finer precision and I wonder if it has made soil nutrient testing obsolete? Did I just invent a new way to fertilize turfgrass? I think that soil nutrient testing is still important to get a snapshot of actual soil nutrient levels but even the MLSN is probably too high in many regards. This method could get you even lower and more precise.....especially with some refinement.

Below is a close up of all the data but only the last month.

The monthly growth ratio is perfect and the greens are perfect (except for the million or so holes currently in them). You can see a big jump in the weekly growth ratio on Oct 12th as we cut them for the first time following aerification.

P and K genki levels are well above 1 so I'm not worried about them at all. In a few days the monthly P genki will drop to zero as it will have been a month since the last application. I won't worry about P until I get less than ideal growth and both P and K genki are above 1. You can see a jump in the growth ratio following the P and K application on September 17th suggesting that they may have been the limiting nutrient as the soil mineralization occurs. I doubt soil mineralization happens perfectly at a ratio that the plants can use so maybe we are getting a good nitrogen release but P and K are lagging or not sufficient?

N genki is currently around 0.5 where it has been for the last 2.5 months. There is still more than enough nitrogen available for the growth we need. As the weather cools down the N genki will naturally go up as you can already see it starting to trend that way. We apply 0.5g N for monthly maintenance as we don't close for the winter. This seems to help during the low to no growth periods of the year and is recommended for disease management.

If the growth ratio begins to dip below where I want it and it's not due to frost or frozen conditions I will apply more nitrogen and see what happens. In the future I plan on adding other nutrients like calcium magnesium and sulfur. It would also be cool to apply some machine learning to this data to figure out what the best running average would be to use. One day maybe.

Now that I have this tool the growth and fertilizer applications for 2021 should be perfect right? We will just have to wait and see I guess. Of course I always come up with this stuff at the end of the season and am forced to wait 7 or 8 months to try it out in the field!

Juicy

How to find success with overseeding new bentgrass varieties.

 

I think it's important to always continue to evaluate what you think you know in golf maintenance. I'm about to take a pretty hard turn with this blog post. It's because the new bentgrass varieties that we now have are completely different than those old varieties. With these drastic improvements come new ways that we can incorporate them into our courses to begin to enjoy the benefits that improved varieties offer golf course playing surfaces and your budget.

Bentgrass needs full sun. Bull shit. Some of the best establishment of bentgrass I have seen has been on my shady greens probably because the seedlings didn't dry out due to the shady conditions. Even under moderate to extreme shade it did just fine.

Bentgrass doesn't like disruption. Not from what I've seen. Don't get me wrong, I totally love the disturbance theory but in order for the bentgrass seedlings to have a hope in hell of making it to a mature plant you need to make space. Ideally you make that space but other times it's due to poa checking out from disease, too hot or too cold, weakening after going to seed or whatever else bullshit reason the poa decided to die this time. Good turf managers can kill poa in all 4 seasons.

Bentgrass is slow to wake up in the spring. Wrong. The only grass that I mow in the spring is bentgrass. The poa is sunken and feeling the hurt from almost no winter fertilization.

You can't overseed bentgrass into poa....wrong. I have never sodded any bentgrass and have greens that are now mostly bentgrass. I guess I'm doing it wrong?

How to successfully seed bentgrass into poa annua.

Don't limit water. Immature bentgrass plants don't have deep roots so don't let them dry out or throw seed when you can keep it wet. You'll need to wait for the bentgrass to mature before you can dial back the water.

Use fertilizer to put the hurt on poa. After years of working to optimize my fertilizer applications to provide just the right amount I have found that poa really doesn't like it when you back off fertilizer rates. Not just nitrogen, but everything. It loves fertilizer and maybe the main reason that poa is so widespread on golf courses is that we generally have been applying more fertilizer than is required because understanding how much is enough is really really hard to do. Use a standard fertilizer amount of 2 g nitrogen/m^2 to start. This will keep the poa alive but not as competitive as the bentgrass. If you go lower, the bentgrass will lose its competitive edge and moss will take over! Even bentgrass needs some fertilizer but it needs much much less than poa so this difference in needs can help you promote bentgrass over poa annua especially at the start.

When weather favors poa over bentgrass your only tool is soil fertility. If you have some cool wet weather, keep the fertilizer in the shed and watch the poa struggle. When conditions favor bentgrass, push that growth!

Maximize disruption when throwing down seed. BIG holes, and lots of them. When we seeded bentgrass last fall I poked millions of small, tightly spaced holes and put seed and sand into them. While we had a good germination in these holes, the plants the matured in many instances were in the deep tine holes that were much larger in diameter and spaced further apart. Give the plant room to mature, then let it do what it was designed to do. Spread out into the poa that is weak due to low fertilizer rates.

Bentgrass spreading to fill in the void (left) vs poa on the right. Bentgrass easily dominates these cup cutter sized holes.

Poa died in this dry fairway opening up space for bentgrass seedlings

It's hard to see in a picture but the 2cm diameter bentgrass plants are in old deep tine holes.

Be patient. If you want instant results then buy some sod. Otherwise you need to be patient and throw seed at every opportunity. I've talked about overseeding and microdose applications already on this blog so go read those posts if you are thinking about overseeding . Generally it will take up to 2 seasons before you hard work starts to pay off. Don't let up, keep throwing that seed!

Let the improved plant do the dirty work. With pest control products that use systemic resistance etc you can give the bentgrass even more of an edge over the poa. As the newer bentgrass varieties have more disease resistance than unimproved poa annua you can boost is further with ISR products further giving the bentgrass the advantage. Of course, disease can quickly wipe out your poa especially with diseases like anthracnose but a small advantage over years can and will result in more bentgrass.

Once you get a good amount of plants to mature, get out of it's way. Let it do what it was designed to do. Dry it down every now and then, stretch those fungicide intervals, forget to fertilize them for a few months etc.

3 years after seeding into winter damage this green is now mostly bentgrass. With this much bentgrass coverage you can start to afford to seriously neglect the poa