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  • peterp17

January 18th, 2023

Hi All,

Well this is a sort of two blogs in one as next Monday I'll be setting up at Harrogate for the forthcoming BTME 2023 show. If you are up for the show and fancy a chat about all things Davis weather station-related and environmental monitoring, please drop by and say hello. Peter Palmer and myself will be in attendance.

You can find us on stand 620 in Hall 6. Along with the class-leading weather station and sensor options, we will also be displaying our new PRP Reporting Software that converts weather station data into simple to download summary reports of climatic and agronomic information including Growth Potential, Growth-Degree-Days, Smith Kerns Dollar Spot Probability Model and Soil Moisture Surplus and Deficit information.

So even if you already have an existing Davis weather station, we might have something for you :)

You can download a floor plan for BTME 2023 below ;

Download PDF • 3.64MB

I also have a link for Headland Weathercheck at BTME, if you want to check the weather forecast. You can find it here

This week I have been up in Scotland with my colleague installing some Davis weather stations and sensors and I hope that'll expand some of the northern data when I'm doing comparisons. I knew I was in for a cold one when I glanced out of the Easyjet flight window to see this beautiful vista on the run in to Edinburgh.

With temperatures dropping down to -9°C overnight in places, you don't need me to tell you it is a tad cold out there but without this sort of weather you wouldn't get beautiful views like this. Mind you after January's rainfall figures we could do with a break, both for the sake of soil health (giving the soil a chance to breathe) and one's own mental health !

To see rainfall data indicating 206 mm in the first 14 days of January for Central Scotland, 150 mm for the West Country and 112 mm for the west of Ireland speaks volumes to what we have endured as an industry. And remembering also that rainfall comes with heavy cloud cover and therefore very little PAR light availability for your grass plant, be that Bentgrass or Ryegrass. I will look at this later in the blog in more detail.

The fact that we now have period of heavy frost and drier weather as a consequence is a godsend because not only does that give the soil a chance to breath but it provides some great natural aeration as the freeze / thaw cycle splits soil particles apart.

So let's look at where we are this week and how long the deep, cold trough pattern shown in the GIF above from is going to last.....

General Weather Situation and outlook - w/c 16-01-2023

So the rest of this week looks like being cold, mainly dry and settled with some snow showers across western coasts and particularly sneaking in from The Severn and Mersey estuaries, as they have a habit of doing when we have north westerly winds.

Bright means cold and I expect to see day time temperatures in the low single figures with continual ground frost up until, but not including Saturday morning across Ireland and Sunday morning for the U.K, when the temperature will begin to rise slowly. This rise marks the transition from a cold temperature trough to a high pressure peak as an Atlantic high pressure system comes into our weather picture.

Moving in from The Atlantic means it'll affect Ireland first and the west side of the U.K next. The change will be subtle and commence with rain moving into the west of Ireland on Friday a.m., but this shouldn't last beyond lunchtime. More rain will make its way into the west of Scotland and Ireland on Saturday and this will try to make inroads inland but fail. On Sunday this rain will break down into showers along western coasts. Away from these two weak, weather fronts, we will be largely dry and dull with temperatures picking up through the early part of the weekend for Ireland and the latter part of the weekend for the U.K, but the change will be slow.

It won't be a sudden transition into dry weather because we have low pressure to the north and south of the U.K, so I expect to see rain across Scotland and further south across the southern half of England on Monday and Tuesday as that high attempts to push these lows out of the way, but in doing so it drags down moist air on its leading front.

Temperatures will rise up to 8-10°C during the day and with more in the way of cloud cover, we will cease to see overnight frosts. By Tuesday that transition to drier weather will be well on the way, but they'll be plenty of cloud around and possibly fog and mist. So it won't be a warm high pressure, but just a stable, dry high pressure with plenty of cloud cover and therefore less risk of frost.

Now it could be that this high pressure sticks around long enough to takes us through January into February but there are plenty of Atlantic low pressure systems around and eventually it will yield. Whatever it will provide us a drier weather window and let things calm down from the relentless westerlies that we experienced in the first half of January.

Agronomic Notes - Let there be light

A slightly clumsy title this week, but I thought I'd continue my look back at 2022 and use some data on Plant Available Radiation (PAR light) to discuss the competitive merits of 2 grass species - Agrostis stolonifera and Lolium perenne.

7-10 days ago or so, I saw a post on FB asking about the relative merits of overseeding L. perenne into greens. Now perish the thought would be many people's first reaction but I've known of a number of Superintendents who have been doing just that for a good number of years, with great results. On small greens, in a heavy wear scenario, it works just fine and modern cultivars will take 3mm mowing no problem if that's your bag.

Now, I'm not here to take sides in this debate, perhaps it's one for the 'mosh pit' of Weatherspoons next week but I thought I'd use some PAR light data to highlight the competitive ability of different grass species in our climate and you'll see why it makes perfect sense from a light perspective.

Before I expand this argument, a little refresher on light.

So the grass plant only uses part of the light spectrum to power the photosynthetic process whereby it converts light energy into food and thereby facilitates growth. The part of the light spectrum that the grass plant uses is known as Plant Available Light or PAR for short and is held to be between 400nm and 700nm wavelength. This wavelength spectrum includes blue, green, yellow and red light and we measure it on a Davis Weather Station by fitting a lovely little sensor made by Apogee called the SQ 212.

It is my fav sensor, but then I am sad.....

In order to quantify a particular plants requirement, we use a calculation called The Daily Light Interval, or DLI for short. This is measured in moles of light per m2 per day.

Now as I have said before, hard and fast, grass species, DLI data is hard to come by, but two 'oft quoted' figures are that Agrostis stolonifera requires a DLI figure of 30 mol m2 per day to grow well and Lolium perenne, closer to 11 mol m2 per day.

I'd love to know what a typical DLI requirement is for Poa annua or Agrostis tenuis for example, but that data just isn't out there as far as I'm aware.

So below is a graph from a Davis weather station located in Central England showing the DLI readings from Jan 1 - Dec 31, 2022. I have superimposed the sufficiency levels for the two grass species above and the date when the DLI hit that figure in the spring and dropped below it in the autumn.

Here's the graph ;

So, for Agrostis stolonifera, the DLI rose above its sufficiency level on the 16th March and more or less stayed above it until the 17th of September, when it dropped away sharply. Now we know or let us say, strongly suspect that Poa annua has a very low DLI requirement, I'd put it under 10 mol per m2 and possibly closer to 5-6 mol per m2.

So, if we are maintaining a grass sward with both Poa annua and Agrostis stolonifera as a constituent, we can see that the Agrostis sp. performs well from mid-March to mid-September, but thereafter would be at a competitive disadvantage (to Poa as an example) from a light perspective. And since light fuels energy production which fuels growth, it would be safe to assume this would translate to a growth disadvantage.

So that's 6 months of the year when it works well and 6 months when it's on the back foot. That is why if you start off with a Bentgrass monosward, it is extremely hard work to keep it pure from Poa annua, because it is at a competitive disadvantage from mid-Sept to the following March, period. And that's before we introduce shade into the argument.

Now let's look at the second grass species, Lolium perenne.

This has a lower light requirement, although I think there's some debate to be had here in how low a DLI actually suits Perennial Ryegrass. Certainly it does not like a shade environment and shows reduced vigour in low light conditions. Hence the requirement for multiple light rigs on modern-day football stadiums with their inherently-low light levels. Nevertheless, you'll often read that Lolium perenne has a DLI requirement of 11 mol per m2, so let's go with that, who am I to argue ?

Looking at the blue line on the graph, drawn at this DLI level, we can see a much longer growing season for Lolium perenne, with a spring kick in date starting at the end of January and not finishing until the end of October. So that's 9 months of the year when light levels are broadly conducive and 3 months when they're not. So it has a much longer growing season than A. stolonifera and that's why for the people who overseed it into greens (or other areas), it works really well. With modern breeding refining this species of grass, particularly in terms of fineness of leaf, you'd like to think that this refinement is giving it a lower DLI requirement, but I'm sort of thinking aloud here.

If any of you grass seed guru's wants to drop by the stand and enlighten me specifically in terms of DLI requirements, I'll be all ears. I'd like to see data mind :)

My next blog will be on Monday week because next Monday is BTME set up.

All the best and I look forward to seeing you all next week if you are up.

Mark Hunt

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Steve Goodier
Steve Goodier
20 янв. 2023 г.

love these weekly Blogs, so educational thank you

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