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  • Writer's pictureMark Hunt

January 15th, 2024

Hi All,

With air temperatures dropping to -4°C overnight, we are in for a very cold week with a significant wind chill effect. Ultimately this is good news for our industry as not only does it give us time to continue to dry down after the unforgettably wet end to December and start of January, but the freeze / thaw cycle will create a natural benefit from a drainage perspective.

I was out over the weekend mountain biking and walking, trying in vain to work off the effects of Christmas and I could see the dry down taking effect already. Wish I hadn't jumped on the scales though when I got home as I can see I have plenty of work still to do !!!

Last autumn I mentioned the potential arrival of some Scandinavian visitors if cold weather continued on the continent. I was talking about Waxwings, a beautiful bird that every winter travels across The North Sea to plunder our berry crop. Most years they tend to be come in limited numbers but this year they are here in force. Took this picture in Leicester yesterday as they targeted Mistletoe berries, the first time I have seen them do this, much to the chagrin of a nearby Mistle Thrush. (now I know where the name comes from). Far from being a country bird, you are more likely to see a flock of Waxwings in a retail park or service area, planted with Rowans or other berry trees. They look very Slavonic to me :)

So let's put some shape on the coming week weather-wise and particularly the threat of snow which is already an issue across the north east of Scotland.

General Weather Situation - w/c 15-01-24

So the GFS image above courtesy of shows a very different weather picture to this time last week when we were sitting under the protection of a high pressure system. This week we start with a pronounced northerly wind direction, hence the change to colder weather from Sunday to Monday, with low pressure across Europe and one sitting to the south west of us. The latter is the one to watch.

So Monday looks like being a 'brassy' sort of day as will a number this week with a very cold, northerly wind but plenty of winter sunshine. Temperatures will struggle into positive numbers with 1-2°C typical in the day and then potentially dropping to -4°C or lower at night with clear skies. This pretty much sets the scene for the week, very cold nights, plenty of winter sunshine, some harsh overnight frosts and a piercing northerly wind. The change to this weather pattern comes overnight into Saturday.

The threat this week comes from snow showers, already an issue across some parts of Scotland and Northern Ireland. Today we may see some showers across the south west of England and also down the east coast but they will be limited inland. Tuesday sees more moisture in the weather picture with wintry showers pushing into Northern Ireland then across into the north west of England and north Wales. These showers may / may not push further south into The Midlands. Later on Tuesday, the showers will consolidate over northern England. A few days ago it looked like we had a significant snow threat from Thursday onwards, but this has largely diminished you'll be happy to hear. So at this stage, minimal snow threat this week BUT keep an eye on your rain radar as this may still change.

Now as we approach the end of the week, we see a high pressure system push up over the U.K and this will change the wind dynamic, swinging it round from northerly to more south westerly, with milder air arriving overnight Friday into Saturday. The isobars will tighten significantly meaning by Saturday morning it'll be extremely windy but feeling milder.

That change in the wind direction will also open up the weather picture to Atlantic fronts I am afraid and the 1st will arrive across Ireland overnight into Saturday. This rain will move eastwards across The Irish Sea during Saturday. As this moisture hits the cold air sitting over the U.K, its leading edge will likely fall as snow, particularly over Scotland, The Pennines and east of England I think. More rain arrives overnight into Sunday, some of this will be heavy but it'll mostly clear by Sunday morning to leave a dry day. Ireland though will be on the receiving end of more rain, this time appreciably heavy and this rain will push quickly across The Irish Sea into western coasts and the U.K mainland during Sunday afternoon. So a wet end to the day on Sunday, mental note, get out of bed and walking early ! Again the leading edge of this rain may fall as snow across Scotland and if so it'll be heavy. The strong south westerly airstream will push air temperatures up into double figures by Sunday.

Weather Outlook - w/c 22-01-24

So over the weekend we see a change away from our welcome run of dry, cold weather and back to a wet, windy and mild one. Now before you roll your collective eyes to the sky at the prospect of the return of wet weather, all may not be lost because next week looks like high pressure is nudging up. Now with low pressure sitting to the north this means the winds are being funnelled between the two systems so next week looks to start very wind, mild and pretty wet with Atlantic frontal systems pushing across the U.K on Monday. Thereafter we look to be into a sunshine and showers type pattern of weather next week with a drying wind between the showers. As we progress through the week, the frequency and intensity of those showers decreases and the wind intensity drops as it swings more westerly. High pressure looks to build at the end of next week to edge rainfall more northerly. So it doesn't look at this stage like a return to December's weather pattern. Fingers crossed that transpires to be the case.

Agronomic Notes

Freeze-thaw cycles

Last week, I touched upon where in some cases less is more when it comes to aeration. This week some of you may be able to get out there and do some vertidraining / Air2G2, etc if ground conditions are conducive.

The plus point though is that even if you can't, Mother Nature will be doing it for you. As we know we have pores in the soil that are occupied with water and when we go through a week like this weather wise, we experience freeze and thaw cycles. So the water in those pores changes from a liquid to a solid and back again from day to night to day. As the structure of the water changes from a liquid to a solid it expands to the tune of 10%. The expansion in volumetric terms is due to the physical structure of ice crystals occupying more space than the structure of water as a liquid. This expansion retraction during the freeze thaw cycle opens up the soil structure and creates fissures allowing better water movement. So Mother Nature will be doing its own aeration this week and we will all benefit. It is the same process incidentally that reduces thick clods of soil after ploughing to a fine tilth over winter. It is more effective in some soil types than others and this will be due to the amount of water a soil holds in its structure and its thermal properties. (how quickly it warms up and cools down)

Dormant Fertilisation

This is I think is an American term but it one that works well at this time of year from a granular fertiliser perspective.

This is particularly the case if the form of fertiliser applied has a mechanism to control the release of nutrients and thereby protect them from leaching. I am therefore talking about slow release, controlled release and organic / organo-mineral fertilisers. In my previous employment I was a big fan of a post Christmas application of this type of fertiliser because it would only release during mild spells of weather between now and the spring.

Why not just apply a liquid fertiliser instead ? Well the problem is that milder at this time of year often means a spell of wet and windy weather, so getting a spray window is tricky, getting a heavy sprayer out vs. a light rotary spreader is also problematic and of course there is the application efficacy. Liquid fertilisers applied during cooler weather tend to be more ammonium and nitrate based (ammonium sulphate / potassium nitrate for example) in order to engender a plant response during cooler weather conditions. These forms of nitrogen are susceptible to leaching from a rootzone so if applied in a liquid form, you will lose a % of what you apply to the environment and that isn't good practice. Better to apply a longer-term granular fertiliser to tick away in the background, releasing a small amount of nutrient during milder spells of weather when we have positive Growth Potential and in a form that is resistant to nutrient loss by leaching.

If the weather obliges between now and the spring (whenever it arrives), you have gained a head start, some useful growth and even better, if you are doing an early aeration, some recovery as well. What's not to like ?

Now in turf management as in life, there are always two sides of the coin. Some people would no doubt comment that dormant feeding along the lines I have described only benefits Poa annua because it is able to grow better at lower temperatures and light levels than other plant species.

There is some truth I think in this however the truth is many superintendents in the U.K & Ireland are managing Poa / Bentgrass swards, that is the norm. Great if you aren't but in my mind, that is the reality. Away from the La La Land, the added reality is that during the calendar year there will be periods of weather / climatic trends that tip the balance towards Poa annua and towards Bentgrass, be that Creeping or Browntop. These obviously relate to PAR light (Plant-available light), temperature and soil moisture. It is the Ying and Yang of fine turf maintenance in this country and doesn't just relate to Poa / Bentgrass, you could make the same observation with Poa / ryegrass and Poa / Bent / Fescue. As a turf manager presenting a surface 24/7-365, with I'd add, the increased expectation courtesy of social media and the associated entitlement gene, you have to work with this balance, manipulate it for sure, but work with it you have to.

So if a period of weather conducive to growth / recovery presents itself, in my mind you take advantage of that fact. All we are talking about here is plant growth and as the days begin to stretch out at the end of January / beginning of February, we pick up better DLI figures and sometimes Growth Potential as well so grass species other than Poa annua benefit.

February 2023 was a very different February to the one we normally experience I admit, being dry and mild, but with the way our climate is heading (this being an El Niño year and all), who is to bet we don't pick up something similar even for a time.

Below is a graph of last February charting out DLI and Growth Potential from a Davis weather station in Central England. It is clear to see the warmer, brighter days last February and if the plant has been able to take up nutrient on the run up to this type of weather, courtesy of an earlier granular application, it will benefit from a growth perspective.

A stronger, better sward coming into March / April means less requirement to apply the commonly touted 40kg of quick start, granular N to wake up your dormant grass sward. No need because you did it months previous with a lot less N and with minimal leaching.

Food for thought maybe ?

Image reproduced courtesy of the USGA®

Freeze / thaw cycles and play

I was flicking through LinkedIn the other day in a rare moment of quiet and found a post by Damian Coleman, Galway Bay Golf Resort showing a USGA video on the whole frost / thaw cycle / root shear dynamic that always comes to the fore at this time of year. Previously I have produced a graphic on this issue, but this is much better.

I think when we get to the end of the week, Friday into Saturday, we could see some issues before the arrival of milder air / warmer water / rain thaws out surfaces. For that reason it may come in handy, thanks to Damian for bringing it to my attention, you can find it here.

Wrap up well this week and don't forget your birdlife in the cold weather, topping up the feeders, putting out some old fruit and a bowl of water go a long way to help them with the wind chill as it is. Whilst I have been typing this blog, the old Blackbird has been landing on the door handle and giving me the evil eye, so once more I reach for the Suet Sprinkles !!!!

All the best.

Mark Hunt

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