Aggressive PGR and N applications and low mowing height impact putting green performance

Luqi Li Author

07/30/2020 Added

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Dr. Bill Kreuser - Aggressive PGR and N applications and low mowing height impact putting green performance

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[00:00:01.020](motivating music)
[00:00:21.470]Alright, this is kind of my mad science lair here
[00:00:24.210]on east campus, this where I get to have some fun,
[00:00:27.050]and we call this my pet project.
[00:00:30.350]It's one of those things I've always wanted to do,
[00:00:32.440]and, decided let's just do it this year.
[00:00:36.620]In putting green management, we're getting more influential,
[00:00:40.370]on like, what is an acceptable level of green-ness,
[00:00:42.920]or quality that the golfers demand,
[00:00:47.940]green speed is always the concern,
[00:00:50.060]but now we're even starting to get into clipping volume,
[00:00:52.020]we're trying to understand how much grass growth do I have,
[00:00:55.300]and what am I trying to manager for.
[00:00:56.780]So, the question that I had was a couple,
[00:00:59.380]one, we're seeing mowing heights go lower and lower,
[00:01:02.840]does that really have a big impact
[00:01:04.560]on like green speed and the playability of the turf,
[00:01:07.906]what does the quality look like?
[00:01:09.950]And so that's not a new creative idea,
[00:01:12.700]I mean I'm mowing some plots here
[00:01:14.600]at either 120 thousands, or 80 thousandths,
[00:01:17.660]so, a little bit tighter, this is V8 creeping bentgrass,
[00:01:21.480]so it can handle the 80 with no problem,
[00:01:24.380]I could even go lower, but the spots would flatten up
[00:01:28.120]and the mowers were really fine bed knife.
[00:01:32.261]But we wanted to look at, how does fertility rate
[00:01:35.020]and PGRs impact or help with turf performance
[00:01:39.000]at these different mowing heights, and so,
[00:01:41.190]we essentially have two different studies
[00:01:42.960]at the same treatments and one is just at a higher height,
[00:01:45.577]and one's at a lower height,
[00:01:47.350]and so, while we don't make a lot of direct comparisons,
[00:01:49.770]between the two, because of how the studies are laid out,
[00:01:53.080]we can generally see what trends are we seeing in one,
[00:01:55.640]or are we seeing that trend in the other?
[00:01:57.280]So, let's set this up.
[00:01:59.910]As I said, we have a sand-based putting green here,
[00:02:02.770]that is mowed at either 120 or 80 thousandths of an inch,
[00:02:06.270]every single day, with the Twirl Flex Mower.
[00:02:10.190]Our treatments then are either a lower fertility level
[00:02:13.420]of 15 hundredths of a pot of nice green fertilizer,
[00:02:16.160]from Uria, every two weeks,
[00:02:18.340]or, then we do three tenths of a pound.
[00:02:21.957]But you might think that's a lot,
[00:02:23.413]like six tenths of a pound a month?
[00:02:25.350]And we'll get into that, but kinda get an idea of like
[00:02:27.470]what does it look like in terms of quality,
[00:02:28.900]performance, or playability?
[00:02:30.440]It might not be as dramatic as you would think,
[00:02:32.580]a little teaser.
[00:02:33.660]So then we have that,
[00:02:34.560]we have those two different N rates
[00:02:35.730]across those different fertilizers, or mowing heights,
[00:02:38.650]and then, a big thing I talk about a lot is
[00:02:42.580]how do we manage our growth rate with PGRs?
[00:02:46.340]And so, the things that we've learned about
[00:02:48.580]in the last 15 years of doing PGR research,
[00:02:51.780]is that if you're mowing at a putting green height,
[00:02:57.530]we know it has some good, growing the green day models,
[00:02:59.800]of course they trim it and for Primo,
[00:03:01.769]and so they have a lot of data in that
[00:03:02.960]and that, we've expanded to all groups of other grasses now,
[00:03:06.210]but we have Primo at the label rate,
[00:03:08.540]of five and a half ounces per acre,
[00:03:10.510]we have a Primo at a six X eight, rate,
[00:03:12.780]so 33 ounces per acre.
[00:03:14.870]And then we have Primo at the label rate,
[00:03:16.840]five and a half ounces per acre,
[00:03:18.930]with the addition of Trimmit at 16 ounces an acre,
[00:03:21.640]so we're doing two high label rates,
[00:03:23.560]with both of those combined.
[00:03:25.240]And what we know from that research is,
[00:03:27.050]if you start mixing those rates together,
[00:03:29.550]we get more clipping yield suppression.
[00:03:32.220]And so we wanted to figure out,
[00:03:33.940]can that increase level of clipping yield suppression
[00:03:37.060]really have big broad impacts on that growth rate,
[00:03:40.310]and on performance and on ball roll?
[00:03:42.500]And then how does that fertility aspect balance it?
[00:03:45.050]So, the analogy that we use is driving growth rate,
[00:03:47.840]where the accelerator pedal of our clippings
[00:03:50.230]is the end rate, and the brake pedals are PGR.
[00:03:53.310]So what this idea here is
[00:03:54.313]that we have our standard, no PGR, just fertility,
[00:03:58.060]we've got our standard Primo rate,
[00:04:00.800]and then we have these like higher pushing the brake rates,
[00:04:03.610]with the Primo-Trimmit mix,
[00:04:04.960]or the high rater Primo in combination
[00:04:07.480]with high level fertilizer.
[00:04:09.560]Alright, so let's kind of get into it.
[00:04:11.240]So we've been doing this study now
[00:04:12.630]since the beginning of June,
[00:04:14.060]we collect data every two weeks.
[00:04:16.230]So every two weeks we go out, we measure green speed,
[00:04:19.090]we measure ball roll, we measure quality,
[00:04:21.560]we measure the green-ness of the turf,
[00:04:24.980]with a remote sensing thing
[00:04:25.993]that we would normally put on the back of a mower
[00:04:28.070]but we just handheld it here,
[00:04:29.830]and then in the month of July,
[00:04:31.530]we even measured the green speed in the morning
[00:04:34.140]before we do our ball roll or do our clipping yields.
[00:04:37.660]That's because clipping yield
[00:04:38.510]really represents yesterdays growth,
[00:04:40.750]so we kinda wanna know,
[00:04:41.730]what do the clipping yields look like,
[00:04:43.710]at the end of the day,
[00:04:44.840]or actually the start of the next day before we mow green,
[00:04:47.210]to get an idea of, did those PGRs
[00:04:49.270]or fertilizers have an effect on our green speed?
[00:04:52.250]So, well just kinda dig into it.
[00:04:54.300]First thing we wanna look at is just the quality of it.
[00:04:56.990]So we just kinda work our way across the plots here,
[00:05:00.450]this plot here you have a high rate of fertilizer,
[00:05:04.126]which is three tenths of a pound,
[00:05:06.230]with Primo at the normal rate,
[00:05:08.900]right next to it, the same amount of fertilizer,
[00:05:11.110]three tenths of a pound,
[00:05:12.440]this is Primo at a 33 ounces per acre,
[00:05:16.200]so a six X rate.
[00:05:17.610]Not a really huge difference,
[00:05:18.890]maybe a little bit greener color,
[00:05:20.750]but honestly, we're not even seeing
[00:05:22.120]that much more difference in clipping yield suppression,
[00:05:24.290]this is about 30%, this is about 40-50%,
[00:05:27.890]so we're seeing more suppression,
[00:05:29.600]but not seeing that much fighting.
[00:05:31.874]As we work our way across, this is your low fertility rate,
[00:05:34.680]no PGR, it looks good.
[00:05:36.490]There's people out there that wonder about, if,
[00:05:39.695]can I grow grass without PGR?
[00:05:42.380]Yeah, I mean it looks fine, maybe a little bit yellower,
[00:05:45.170]maybe the leaf textures a little bit different,
[00:05:47.140]but you can get an idea of what that looks like,
[00:05:50.602]now this is that same goal right now again,
[00:05:52.330]with that three X rate of Primo,
[00:05:53.940]so again, it seems pretty good,
[00:05:55.630]a little bit darker than the control,
[00:05:57.380]not anything too crazy,
[00:05:59.420]and then we go over and start adding Trimmit.
[00:06:01.610]So, here's the low rate of Trimmit,
[00:06:04.230]or the full rate of Trimmit, and the full rate of Primo,
[00:06:07.520]mixed together, and all these PGRs are being applied
[00:06:10.340]on growing degree days, that are in our green keeper app,
[00:06:12.400]full is about, I think about 280
[00:06:14.630]growing degree day reapplications are involved.
[00:06:16.730]And we're really starting to see
[00:06:17.740]that the canopy is much different and in texture,
[00:06:21.280]and color, and quality,
[00:06:23.000]I still wouldn't say it's unacceptable,
[00:06:24.780]it just has a little bit different appearance to it,
[00:06:26.680]and at three tenths of a pound of nitrogen,
[00:06:28.890]it really isn't that bad.
[00:06:30.800]We go to the plot next to it though,
[00:06:33.260]and now we're at low end with a lot of growth suppression.
[00:06:37.330]Our clipping yields are really low here,
[00:06:39.360]and it's really-- we're golfing in pretty poor quality.
[00:06:42.740]So, we're getting to the point
[00:06:44.119]where this is marginally acceptable quality.
[00:06:49.692]And then finally, we just have our
[00:06:52.911]high rated fertilizer by itself, with no PGR,
[00:06:57.000]and then this last plot here is low rate with Primo,
[00:07:02.420]so can really the see the gamma of what this looks like,
[00:07:05.570]so you have the high rates of Primo,
[00:07:07.860]not really causing a problem,
[00:07:09.830]and when you mix these high PGR rates
[00:07:12.710]with a high rate of fertilizer,
[00:07:14.800]you know, the grass looks pretty darn good,
[00:07:16.660]we can push the growth rate that way.
[00:07:19.130]This is at 120, pretty standard mowing height
[00:07:22.030]across much of the golf industry for bentgrass greens,
[00:07:24.480]now let's swing over this way now,
[00:07:26.570]and now we can really see the differences
[00:07:29.140]when we bring things to eight.
[00:07:31.678]Now, this a bentgrass putting green mini,
[00:07:34.520]and it looks a little bit lighter in color,
[00:07:37.750]the quality's not as high, there's just not as much
[00:07:40.150]leaf area there to give it that green color,
[00:07:43.220]but I wouldn't contend
[00:07:44.250]that it's really that much unhealthier,
[00:07:45.970]I have nice roots still on this plot,
[00:07:48.920]and so I'm feeling pretty happy with it,
[00:07:50.990]I think it is a little intense maybe at that mowing height,
[00:07:54.100]but, maybe not too terrible,
[00:07:56.300]and as we start to look at these plots,
[00:07:58.490]we have the high rate of Primo
[00:08:00.280]with the high rate of fertilizer,
[00:08:03.070]we have the high rate of Primo
[00:08:05.930]with the lower rate of fertilizer,
[00:08:07.150]so we can kind of see the fertility affect right here,
[00:08:09.667]that this is kind of a little bit lighter,
[00:08:11.190]here's a little bit darker,
[00:08:13.597]and you might think, well, double the fertilizer,
[00:08:15.620]what kinda impact is that having on green speed,
[00:08:17.760]and clipping yield?
[00:08:19.420]Not as much as you'd think.
[00:08:21.880]Here's the high rate of fertilizer by itself, with no PGR.
[00:08:25.750]This is the Trimmit-Primo mix with low fertilizer,
[00:08:31.410]so again, you look at that candy texture it's really tight,
[00:08:35.350]and I don't know if you can really zoom in here,
[00:08:37.040]and you can see how tight that is,
[00:08:39.100]we don't even do brushing or anything,
[00:08:40.490]it's just mowed tight, and that's how a lot of these look,
[00:08:43.710]but, the canopy texture, it's a little bit different,
[00:08:47.130]the colors a little bit different with the Trimmit there,
[00:08:50.300]this is mowing low with low fertilizer,
[00:08:52.900]and it's kinda going the wrong direction,
[00:08:54.730]it's been getting a little bit more
[00:08:56.290]and more yellow as the year's going on,
[00:08:58.230]and so, I think if you're mowing at these lower heights,
[00:09:01.149]you have to start increasing your rate,
[00:09:03.210]and I'll talk about that in a second.
[00:09:05.870]This is the high rate of fertilizer
[00:09:07.440]with that high rate of Primo.
[00:09:08.840]So that's six X rate, again,
[00:09:10.550]I mean look at how dense this is,
[00:09:12.130]this is a beautiful surface,
[00:09:13.380]it looks like the felt of a pool table, it's so nice.
[00:09:17.350]And then we have our low rate,
[00:09:19.400]with the standard rate of Primo, doesn't look terrible,
[00:09:22.530]a little better than the without Primo,
[00:09:24.020]so that's definitely helping,
[00:09:25.590]and then again, this is our last one.
[00:09:27.280]This is that Primo-Trimmit mix,
[00:09:29.370]with a high rate of fertilizer,
[00:09:31.380]and wow, it is really a nice looking surface,
[00:09:35.020]maybe a little bit of that typical class B DMI type color
[00:09:41.350]you would see from something like a pack of beach is all,
[00:09:43.580]or from any kind of a DMI product, so,
[00:09:46.510]really big differences in quality.
[00:09:48.210]So let's start to get into some of those other things
[00:09:50.050]that are harder to see.
[00:09:51.895]So the first thing I wanna talk about is clipping.
[00:09:55.866]So we've got grass here mowed at 80,
[00:09:57.340]grass over there mowed at 120,
[00:09:59.500]which one do you think is growing slower?
[00:10:01.700]Intuitively you might say
[00:10:03.180]the grass growing in 80's growing slower,
[00:10:05.060]it has less leaves to make sugar,
[00:10:06.840]so if it has less leaves to make sugar,
[00:10:08.690]you would expect maybe it's growing slower.
[00:10:10.760]In fact, that couldn't be more wrong.
[00:10:13.360]So we only have a few of our clipping dates
[00:10:15.600]analyzed over the summer, but just to give you some idea,
[00:10:19.030]our first starts of clippings from mid June,
[00:10:23.280]this side at 80 was drawing at 1.9 grams per meter squared,
[00:10:28.430]of clippings a day.
[00:10:30.010]So don't worry about the units too much,
[00:10:31.280]just listen to the number, 1.9, it's a lot.
[00:10:33.993]Over here, that same plot is growing at 0.38,
[00:10:38.890]so a huge reduction in clippings on that side
[00:10:41.720]compared to this side.
[00:10:42.877]Now you might think, well maybe it's cause
[00:10:44.440]you started bringing the mowing heights down.
[00:10:46.170]Okay, so then we come back to the end of June,
[00:10:48.500]we do our measurement.
[00:10:49.840]And now the clipping yields on both sides
[00:10:51.700]have slowed way down, and we see this a lot in June.
[00:10:54.640]So if this side, the 0.8 inches side,
[00:10:59.030]is still growing at 0.35, so pretty similar
[00:11:01.980]to how the other side was growing in early June.
[00:11:04.630]But now the grass that's mowed at 120,
[00:11:06.950]is growing at 0.19 inches,
[00:11:09.030]so still double the amount of growth
[00:11:11.520]at this lower mowing height, than the other side.
[00:11:15.020]And then we looked at an early July application, or mowing,
[00:11:19.040]and this side again, 0.8 grams, that side,
[00:11:23.160]a little higher mowing height, to 0.45 grams.
[00:11:25.780]So we doubled our clipping yield again.
[00:11:27.650]And unfortunately, we don't have
[00:11:28.884]the late July numbers ready yet,
[00:11:31.370]because we still have to clean
[00:11:32.277]the sand debris from top dressing,
[00:11:34.662]but really, really remarkable differences
[00:11:37.410]in our clipping yields in those first three,
[00:11:40.120]despite being at a lower mowing height.
[00:11:43.120]So let's get into what you guys probably really care about,
[00:11:45.310]green speed, what is going on with green speed?
[00:11:47.440]So we use one of rockin' suaves modified stint meters here
[00:11:50.630]to measure our green speed,
[00:11:52.250]and we do it a couple different ways.
[00:11:53.450]So again, we measure in the morning before we mow,
[00:11:59.210]and then we mow, and then we measure it again.
[00:12:00.680]So we get an idea of what
[00:12:01.570]yesterdays green speed was at the end of the day,
[00:12:03.870]versus the after mow green speed.
[00:12:06.480]And so I'll even just kind of talk about,
[00:12:10.050]well first let's talk about it generally,
[00:12:11.500]across all the days, averaged together.
[00:12:14.390]So when we're mowing at 80,
[00:12:16.260]our highest green speed on average was 12 feet.
[00:12:20.050]When you mix it with Trimmit and Primo mixed together.
[00:12:23.310]And then with the high rate of Primo,
[00:12:25.060]we got a green speed of 11 feet eight,
[00:12:27.560]the lower rate was 11 feet five,
[00:12:29.338]I noticed the two are statistically the same,
[00:12:31.114]and then the non-Primo treatment was 11 feet two, at eight.
[00:12:36.050]Okay, so we're looking at almost a foot,
[00:12:38.640]so 10 inches of range in our green speed,
[00:12:40.640]and that is perceivable by golfers.
[00:12:43.020]If we go over to this side,
[00:12:45.218]the green speeds on average are still pretty high.
[00:12:47.740]So we're still at about our--
[00:12:49.327]the Trimmit treatment had a green speed average of,
[00:12:51.793]over the whole study, 12 feet one inches,
[00:12:55.200]and then the Primo effects though, weren't as big,
[00:12:58.070]and so we had 11 and 10 feet, 10 inches,
[00:13:01.690]and then the non-treated control,
[00:13:03.270]on average across all of these,
[00:13:05.010]was only 10 feet four inches.
[00:13:07.420]So we were getting nearly
[00:13:09.290]a two foot increase in green speed,
[00:13:11.637]with the Trimmit treatment over here,
[00:13:13.780]when you have this different kind of canopy structure,
[00:13:16.230]and that mirrored what we saw
[00:13:17.250]having to do with mow on eight.
[00:13:19.460]Okay, so, and then the Primo helped a little bit,
[00:13:22.340]but not as much as that Trimmit did,
[00:13:24.360]the Trimmit-Primo combination.
[00:13:27.060]How about after mowing, how did that look?
[00:13:29.090]And so, let's talk about that
[00:13:30.840]with just respect to the last two months,
[00:13:34.450]or this last month, the last two readings,
[00:13:36.400]so the plots that were receiving Trimmit,
[00:13:39.797]in the beginning of July,
[00:13:41.490]they were running 13 feet at eight,
[00:13:44.530]the plots that weren't receiving Trimmit or Primo
[00:13:47.310]were running 12 feet two inches, so again,
[00:13:48.970]a 10 foot increase in green speed.
[00:13:51.367]And the primo treatments were somewhere in the middle,
[00:13:53.630]generally between 12 four and 12 six.
[00:13:56.600]Then we go over to this side,
[00:13:59.760]and again, even though we're mowing higher,
[00:14:01.490]and the grass is growing slower,
[00:14:03.580]so the Trimmit side over here,
[00:14:05.620]is still running at 13 feet eight inches,
[00:14:09.550]is the highest they're gonna go, so a really fast plot,
[00:14:12.410]the non-treated, still going pretty good,
[00:14:15.080]12 feet three inches, so we're still getting
[00:14:16.940]a lot of clipping yield out of that.
[00:14:19.530]And so that was in early July, and then in late July,
[00:14:22.960]the story's a little bit different, especially at 120.
[00:14:26.170]At 80, we saw that Trimmit was the fastest,
[00:14:29.358]about 10 inches faster than the non-PGR,
[00:14:31.340]you can pretty much put it in the middle right between that.
[00:14:34.260]When we were mowing at 120, the standard mowing height,
[00:14:37.020]we are still getting 12 and a half feet,
[00:14:38.807]but we mixed Trimmit and Primo together,
[00:14:41.490]if we didn't, our green speed was down
[00:14:44.470]at 10 feet 11 inches,
[00:14:45.790]so a lot slower when we didn't put any PGR in,
[00:14:49.390]and the primo treatments, again,
[00:14:50.640]were somewhere in the middle,
[00:14:52.079]around like the low 11 feet range,
[00:14:54.340]and so, that combination of Primo and Trimmit
[00:14:56.820]is really having a pretty dramatic effect.
[00:15:00.920]Somethings we are gonna notice,
[00:15:02.990]if you start getting intense
[00:15:04.330]with our low clipping yields and growth rates,
[00:15:07.570]we're starting to see some moss,
[00:15:09.350]and so that's something that we're gonna worry about,
[00:15:11.290]we're seeing it on both sides,
[00:15:12.870]but especially the low fertility rates,
[00:15:14.930]especially with the Trimmit, or the low mowing heights
[00:15:17.730]with the low fertility rates.
[00:15:19.150]Those sort of get a lot of moss in them,
[00:15:22.097]and so, just kind of one of those things to keep in mind.
[00:15:27.150]So, we're stilling having two more daily data collections,
[00:15:30.190]maybe three, through August and September,
[00:15:33.700]continue to study, it's a lot of fun,
[00:15:36.330]we're really seeing some big differences here
[00:15:38.220]and some things that are really important,
[00:15:39.920]and so, take home points now.
[00:15:42.080]If I'm trying to manage for green speed,
[00:15:44.440]mixing PGRs really does seem to suppress that growth rate,
[00:15:49.970]and increase our green speeds compared to the control.
[00:15:53.390]The more suppression we're getting,
[00:15:55.010]the more green speed increase we're getting,
[00:15:57.990]and that's what people have been seeing,
[00:15:59.759]what they really haven't been seeing in lurcher.
[00:16:01.530]The other side of that too is
[00:16:03.110]the fertility aspect on ball roll distance
[00:16:06.159]and clipping yield is minimal,
[00:16:09.990]so there is no significant difference in clipping yield
[00:16:12.690]between 0.15 pounds every two weeks, and 0.3.
[00:16:16.330]It really didn't have that big of an impact.
[00:16:19.010]And then there was barely any difference in green speed
[00:16:22.330]at 0.15 or 0.3 across all the PGRs,
[00:16:25.600]it's generally about 2.3 inches only.
[00:16:28.600]But look at the quality you're getting.
[00:16:30.710]So you can still have grass that is running really quick,
[00:16:33.690]like the high rates of fertilizer with the Primo-Trimmit,
[00:16:37.490]and have good looking quality,
[00:16:39.430]and you don't even need to mow at 80,
[00:16:40.791]'cause we're still mowing at 120
[00:16:41.687]and we're still seeing really good quality at 120,
[00:16:44.640]with those in combination.
[00:16:45.910]So, continue to follow this research,
[00:16:48.580]we'll have a much more thorough wrap up later,
[00:16:51.560]hopefully this winter,
[00:16:53.660]and we'll hopefully replicate this again next year,
[00:16:55.590]so that we can get this information out and published,
[00:16:58.910]so, thanks for your interest in this study,
[00:17:02.070]and for joining the Nebraska Field Day in 2020.
[00:17:06.135](motivating music)

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Aggressive PGR and N applications and low mowing height impact putting green performance

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