Monthly Archives: August 2019

August 19th

You get an idea of what a wet August we have had when you pitch up on the River Trent and it looks like this….. The above picture may look idyllic enough but the river is at least 6 ft above normal summer level and pulling through like a train. All that energy going to waste……

So we head into the 3rd week of August with summer still on hold and an April-like weather scenario of sunshine and showers firmly established. Looking at the next 7-10 day GFS output, there’s so much uncertainty about where our weather is going that even to forecast a week away is tricky currently but I will have a go. Next weekend is MotoGP at Silverstone, last year it was cancelled because the track flooded and since they have spent a fortune resurfacing and facilitating better drainage. It may just be put to the test again 🙁

Image courtesy of tropicaltidbits.com

General Weather Forecast

The above image shows the scenario we start the week with, that of low pressure still calling the shots especially in the north / north-west of the U.K / Ireland who sit closer to the centre of the low. Very much a north-south divide this week in terms of temperature and rainfall with the north and north-west on the receiving end.

So Monday starts not bad really considering the image above with many places starting dry but we do have some showers already building along the Severn Estuary, the west coast of Ireland, The Lakes and Borders. As we move through the morning those showers will consolidate along western coasts of Ireland and the U.K by midday and then push inland through the course of the afternoon clearing the west as they do so. Between these showers it will be bright and breezy with some places staying dry all day. Temperature-wise we are looking at similar to the weekend, so high teens to just nudging 20°C. So a sunshine and showers scenario starts the week, but will it continue ?

Tuesday starts off dry for pretty much everywhere but with low pressure close by it is unlikely to stay that way. So by morning rush hour we see rain push into south-west Munster and then Connacht and this rain will head east over Ireland during the course of Tuesday morning / early afternoon. Across The Irish Sea we have a dry start for the majority of the U.K with just some rain lurking across north-west England / The Lakes. This rain will push some showers across northern England and The Borders through the course of Tuesday afternoon. Further south we look to be largely dry and set to enjoy some pleasant sunshine. By Tuesday evening that belt of rain will have largely cleared Ireland and will be pushing cloud into the north and north-west of England with some showers across North Wales. Temperature-wise 16-17°C across Ireland and Scotland pushing into the low twenties further south.

Overnight into Wednesday and that rain across Ireland will make landfall across western Scotland and north-west England so some showers across north-western coasts from the off. We may also see some showers across South Wales early doors. By the time we hit the Co. Sligo rush hour the west of Ireland will be feeling the effects of the next Atlantic low stacking up to affect our weather with rain pushing into the west of Ireland through Wednesday morning. Further east we look to be largely dry except for some patchy rain over northern England. This low pressure will be moving quite quickly so by mid-afternoon it’ll already be pushing into north-west England and western Scotland. Very much a north-south divide then because south of The Pennines will see a much nicer day, pleasantly warm with long sunny spells and temperatures in the low twenties with a lighter westerly wind as well. For Scotland and the far north of England, the boot is on the other foot with a very wet end to the day I am afraid.

Overnight into Thursday that rain clears Ireland but it’ll push rain into Wales and the north-west of England in the early hours. Some of these showers may push inland a little but they are projected to fizzle out. So first off on Monday morning we may see some cloud cover and one or two showers drifting across Wales and north west England / Scotland but it should be largely dry. Through the course of Thursday morning that low will push further rain into Connacht, Northern Ireland and western Scotland but at this stage that’s where it is projected to stay. So away from that rain front another pleasantly warm and dry day for England and Wales with moderate south-westerly winds and temperatures pushing up into the low twenties again.

Closing out the week and it’ll be 1st practice for MotoGP at Silverstone……

So when Mr Rossi & Co. venture out into the cool Northamptonshire air first thing on Friday morning, what awaits them ?

Well a very nice day is the answer with early cloud breaking to give long spells of summer (?) sunshine and temperatures pushing up to the mid-twenties. Cracking. So dry, sunny and warm across England and Wales again on Friday but across The Irish Sea we have another rain front pushing into Connacht and heading north and east across Northern Ireland and into western Scotland. South and east of this, Ireland should be dry but dull with plenty of thick cloud courtesy of that low pressure system across the west but breaking to give some sunshine as well. Temperature-wise similar to Thursday with 16°C across Ireland and Scotland but pushing up to 23°C for England and Wales. Winds will be light and from the south-west for England and Wales and strong to moderate for Ireland and Scotland.

Well onto the weather for the weekend, hmm tricky one as I’ve seen at least 4 different weather scenarios for Sunday. So here goes…

So Saturday looks like continuing that north – south divide with a line of rain stretching from Kerry across Ireland / Northern Ireland up into western and Central Scotland. West and north of this line will see plenty of cloud and rain I’m afraid. South and east across Ireland should be drier but dull I think. Across The Irish Sea we look to have a much better scenario with early cloud giving way to longer spells of sunshine and warm weather. Temperatures look to rise significantly on Saturday possibly up into the mid-twenties with light winds. The real question mark is on Sunday with a low pressure sitting north-west of the U.K and another one across The Bay of Biscay. It’s the latter that could spoil the party at Silverstone but at this stage it’s going to be so difficult to call. What we could see is the weather breaking down across the south and showers breaking out during the course of Sunday afternoon across central and northern parts of the U.K. Elsewhere looks a much better day than Saturday for Ireland and Scotland with some showers continuing to affect the west of Scotland. It could potentially be hot and humid across the south raising the prospect of thunderstorms but let us hope not.

Weather Outlook

With all the uncertainty around current GFS forecasts, I’m a bit reticent about this one but saying that last week’s outlook for this week is pretty accurate. So next week looks like carrying over some of the unsettled weather associated with that northerly low pressure so potentially continuing wet and windy and on the cool side for the west and north. Thereafter though a much better picture images with an Atlantic high pressure system projected to push in through the course of next Tuesday bringing more stable dry and fine weather for the U.K and Ireland. So fine, dry and warm particularly through the second part of next week before a new low pressure arrives to potentially bring unsettled weather to the north and west next weekend. Now it is the first time for quite a while that I’ve seen a high pressure push in from the west so this could mean a fine and dry start to September. Fingers crossed.

Agronomic Notes

It’s all in the rain you know…

Image courtesy of NetWeather’s lightning archive

Since we have got quite a bit of summer rainfall (at least it is warm rain) I thought I’d kick off with a chat about that. So in early August we had a big thunderstorm here with some pretty close lightning activity close by. Yours truly was out positioning a sterilised container and funnel to get the most of the rain whilst staring up into the heavens wondering when the next strike was due. We had one strike that was instantaneous lightning and then thunder, a wham, bang, thank you Ma’am kind of moment 🙂

So Wendy kindly forwarded me the chemical analysis results of the afore-mentioned rainfall this morning and they made interesting reading.

The pH of the rain from that storm was down at 6.0, so moderately acidic. It contained the equivalent of 0.55 kg per ha of N per inch of rain (How’s that for a mix of metric and imperial units) which by most standards isn’t much really for a lightning storm.

It also had a significant dollop of sulphur (12mg/l)  (which is unusual nowadays since we closed our coal-firing power stations and the equivalent to 3kg per ha of sulphur per inch of rain) and a smidge of sodium and chloride suggesting that it picked this up from the sea on its way over I guess. The pH of the next storm I measured came in at 6.3 so we’ve been getting some nice acidity in the rain this summer if these samples are anything to go by.

Soil Moisture Status – 2019 vs. 2018

Continuing my rainfall theme, I graphed out the theoretical soil moisture status comparing 2019 with 2018 starting at June 1st to the present day at The Oxfordshire location. Now this is one of the drier locations in summer 2019 and I am sure if I had access to daily rainfall and E.T totals from a more northern / western site, the results would be very different.

So in 2018, in the period from June 1st to August 18th, we had 41 mm of rain and 303 mm of moisture lost by E.T making us -262 mm soil moisture status.

In 2019, over the same period  we had 119.2mm of rain and 249.7 mm of moisture loss by E.T, making a soil moisture deficit of 130.5 mm.

It is interesting to me to think that we have still experienced a relatively high E.T summer with only 18% less total E.T than last summer for the same period. So the desiccation pressure on the grass plant has been significant. The difference has been in the rainfall totals with another 78.2mm of rain this summer vs. last and that has made all the difference. That rain hasn’t all fell in one great dump either, it has been spread out across the period so rather than 80 odd days without rain, the longest period for this site has been around 17 days, strangely at the start of July and again at the start of August, weird ?

As mentioned above this location at Thame, Oxford is notoriously on the dry side but it just goes to show the E.T stress on the plant has been significant this year especially on un-irrigated outfield sites but the saviour has been the summer rainfall.

Disease Activity

Following on from a wet week with extended periods of both soil and leaf wetness it is no surprise that we have plenty of disease activity out there.

Summer 2019 is definitely the summer of Fairy Rings with them cropping up everywhere from greens to fairways to outfield and cricket squares. I was listening to the cricket commentary the other day trying to avoid some monotonous current music or ineffective politicians and I heard one of the commentators mention the presence of Fairy Rings and their likely effect on ball bounce. 

Treatment of Fairy Rings is a tricky affair because the depth that they are active varies from right in the surface (Superficial Fairy Rings usually) to deep down the profile. Strobilurin chemistry will have an effect but you have to get the chemical into the active zone of the fungus and so combining it with a soil surfactant is very important. I always suggest doing a droplet test on a core taken from the active area to determine where the fungus is active in the soil profile. The image above shows surface activity of Basidiomycetes causing the rootzone to become hydrophobic but on well-established Fairy Rings, it is present much deeper and so requires spiking / tining period to treatment to get the best result. Often the issue is purely aesthetic as we see the characteristic green rings resulting from the conversion of organic nitrogen to mineral N. For many they aren’t as great concern until the telly cameras get hold of them that is 🙂

With high pressure looking to make a potential appearance at the end of August / beginning of September we should get a quieter period from a disease perspective. Amen to that.

OK short and sweet today as the T.T.D (Things-to-do) list beckons……

All the best.

Mark Hunt

 

August 12th

Hi All,

This picture tells a story, nearly ripe Winter Wheat in the field, some lodging in the crop where its gone over and another dollop of rain on the way for August.

After 34 mm over the last 3 days there appears no let up in the wet summer we have endured.

The temperature / rain combination has had many consequences, a big diesel bill for one as outfield areas just keep on growing when normally a lack of moisture would have curtailed growth. Nature is out of sync as well with everything coming early this year as there’s been no dry summer to force a halt to growth.

I can see this in my garden. The Rudbeckia above are normally about 6-7ft tall and flower in July but the constant moisture has meant more vegetative growth and they’re currently around 10ft now and a right pain to keep upright ! These lovely Japanese Anenome (right) are in full bloom and started at the end of July when I normally don’t expect them to flower till September. In the hedgerows, Blackberries are really early as will be the berry crop for sure. And all because the wet summer has put nature into overdrive. So if your club secretary, financial director, etc wants to know why the diesel bill is up this year, you can point to the garden to show him why.

It’s one of the drawbacks of GDD and G.P models that only temperature is taken into account when estimating growth and so 2019 appears as a lower / similar growth year than 2018, but last years drought stopped growth for 6-8 weeks on outfield whereas this year it has continued nearly unchecked since late May.

You can’t measure this effect in terms of GDD / G.P.

So is there an end to the successive low pressure systems that have blighted our summer (from a holiday perspective) but in all honesty have given us less stress from an irrigation perspective and an easier life for once ?

Maybe…

General Weather Situation

So we kick off Monday with the low pressure that brought gale force winds and rain over the weekend exiting stage right into The North Sea. It is still an unsettled picture though with showers across the south and north-east of England and a rain front pushing into the west of Ireland during the morning and moving east across the whole country during the afternoon. A better picture for the U.K with a lot of areas enjoying a drier day except for the south-east of England, north-east of England and north-west of Scotland where rain will push in for the 2nd half of the day. As we head towards the evening that rain will clear the west of Ireland but will intensify over Central Scotland. Showers will also be reluctant to leave the south-east and north-east coasts of England. A cool day with a single figure night making it a cool start as well and temperatures only in the high teens, subdued by a moderate to fresh north-westerly wind.

Tuesday is probably the direst day of the week for many with the U.K and Ireland enjoying some nice spells of sunshine. It won’t be completely dry though because they’ll be showers across Kerry, Mayo and Galway during the morning and also some showers affecting both western and eastern coastal areas. As we progress through the morning these will dissipate in most areas except over Scotland where morning rain across the north-west of Scotland will drift inland to affect central areas for the 2nd half of the day. Remaining cool for the time of year because of the moderate to fresh north-westerly wind in place for the beginning of the week, so temperatures remaining in the high teens.

As we progress into Wednesday we see a new Atlantic low pressure system usher its way in overnight bringing heavy rain to Ireland, the south-west of England, Wales and the west coast of England by dawn. This rain will move east quickly clearing Ireland during the first part of the morning and affecting all areas of the U.K by midday so a wet day for many on Wednesday. By the evening this rain will have cleared Wales and the west of England leaving behind a showery outlook which will also affect Ireland during the 2nd part of the day. By dusk on Wednesday the rain will have cleared most of the U.K with the exception of north-east and northern Scotland above The Moray Firth. Not surprising then that Wednesday is another cool day with temperatures in the mid-teens under all that cloud cover and rain.

Onto Thursday and a better day with some areas looking to stay dry all day. There will be rain around however and at this stage it looks to affect along a line extending from North Wales across northern England up to The North East. During the afternoon we will see these showers push inland to affect The Midlands and northern England with the north-east of England and eastern Scotland also in the firing line. Later these showers will push south into North London and East Anglia. Save for a few showers across the south-west tip of Ireland, Thursday looks to be a dry one for you after the wet start to the week. With a westerly wind now in situ, we see the temperature nudge up towards the high teens for Thursday across all areas except Scotland where we remain on the cool side.

Closing out the week on Friday and I am afraid we have another deep low pushing in from The Atlantic with packed isobars and plenty of rain 🙁 Overnight into Friday and we can already see this low pressure bringing strong winds and rain to Ireland and the west of Scotland. By rush hour it’ll be across Ireland, The South West, Wales, north west of England and Scotland and during the morning it’ll sink south and east bringing a wet end to the week especially for the north and west. At this stage it looks like the south and south-east will stay dry till the evening so not too bad a day for you guys really. So closing out the week on Friday evening and we will see heavy showers spread all over the U.K with a new rain front pushing into the west of Ireland. There may be a temporary respite for the east of Ireland though on Friday evening as one rain front moves through. Again remaining on the cool side with temperatures only in the mid to high teens perhaps across the south of England.

No surprise then that the outlook for the coming weekend looks pretty similar to the one we have just had with low pressure in charge. So Saturday looks wet and windy with high winds and some particularly heavy rain for the south of England possibly. By Saturday evening the worst of that rain is away so Sunday looks a better day, still sunshine and showers though. with temperatures in the mid to high teens and hopefully a gentler wind so I can go fishing 🙂

Weather Outlook

So another week passes making for a cool and wet August but is this weather pattern here to stay or will the jet stream take a hike up north and allow some warmer weather for the last part of the month ?

Well next week looks to start off as a dead ringer of this week with a cool, unsettled and showery outlook for Monday and Tuesday. We have yet another Bay of Biscay low pressure pushing through mid-week, next week so that means a potentially wet one for the south of England and then as we head towards the August Bank Holiday there’s a suggestion that we may pick a transient high pressure from Friday onwards which will give us a dry and warm interlude. Personally I’d be delighted as I’m at Silverstone for MotoGP that weekend and don’t want another wash out so fingers crossed. Lots can change before then so we will see.

Agronomic Notes

It’s been a strong growth summer….

Taking up on one of the points I mentioned earlier is the failure of the GDD  and G.P models to describe the differences in growth we have experienced in 2019 vs. 2018.

If you look at the data starting from June 1st for each year, the total amount of growth is practically identical till yesterday’s date in terms of measuring it with Growth Potential. The reality is something different because last year growth was moisture-limited whereas this year it hasn’t been.

Let’s look at that period from June 1st to the present day for 2018 and 2019 at a Northampton location ;

You can see that the total Growth Potential is nearly identical, 63.33 for 2018 vs. 62.02 for 2019.

If you count the number of rain days and rainfall though it paints a very different picture ;

 

So we have seen more rainfall, more rainfall days and a much shorter period without rain at this location in summer 2019 vs. 2018.

It is this phenomenon that has caused non-irrigated fairways, rough and sports outfield to continue growing strongly. I appreciate it isn’t the same everywhere as rainfall is anything but consistent. Just 30 miles or so as the crow flies to our Thame location and they’re sitting on 1.4mm for the month vs. 43.4mm for this location near Northampton.

Thanks as always to Rob and Sean for their data 🙂

Disease Activity

As I noticed some absolutely huge puffballs (sorry about the legs :)) and circles of Type 2 and 3 Fairy Rings on pasture land yesterday whilst out walking I pondered on the much greater disease pressure we are seeing this summer than last.

It follows that with more rainfall we have had higher humidity and this has played into the hands of turfgrass diseases like Fairy Rings, whose activity is very influenced by humidity.  Earlier this month I noted how this year was tracking in a very similar vein to 2014, our last high Anthracnose pressure year and I have noted a higher incidence on my travels. Alongside that we have seen more Waitea patch, Rhizoctonia solani, Microdochium nivale and I think we may also see some late summer Take All due to the cool, wet August period.

Higher Microdochium nivale activity earlier this autumn ?

Aside from the ever-present threat of Anthracnose, we also have to consider that this summer we are likely to be carrying a higher level of active Microdochium nivale into the autumn compared to last year because of the cooler, wetter weather. Last autumn our Microdochium didn’t really get started to mid-late October with the heaviest periods of activity much later into November and then that Christmas – New Year period. If this weather pattern continues then to me it seems logical that we will carry a higher inoculum loading into September and October and that could make life tricky in terms of disease management.

To me our strategic aim must be to stop the disease establishing a population from Day 1.

Now this is more easily said than done these days because the tools in our toolbox aren’t what they were. For this autumn most end-users have some propiconazole A.I-containing products in stock so the decision will be when to use these products best to minimise Microdochium populations. Do you go early or keep your powder dry till later in the autumn ?

My feeling is if you can see those all too familiar copper blotches across your sward through August and September then you can expect some early Microdochium pressure in October but of course this all depends on the weather. Microdochium needs plant leaf wetness, humidity and high overnight air temperature to do its worst along with poor drying conditions (light winds).

One strategy then might be to apply an effective fungicide early to lower the inoculum level going into October.

Its worth remembering that in autumn 2020, we won’t be able to use propiconazole but hopefully we will see some new products from the likes of Bayer and Syngenta to boost our ability to control this damaging turf disease. (ending on a positive note)

Ok that’s me for this week, Tempus fugit and all that…

All the best.

Mark Hunt

 

 

 

 

August 5th

 

Image courtesy of Tropicaltidbits.com

Hi All,

The screenshot above of the current position of the jet stream, high and low pressure systems and temperature tells the story of August 2019 I think, at least for the next 10 days. A low-lying jet stream is allowing Atlantic low pressure systems to dominate and so we will see a succession push in over the next 7-10 days bringing cooler and wetter, unsettled weather to the fore. This will have some positive and negative consequences for turf management, more on that later.

After naturalising my garden last year, it’s been great to see that my resident Hedgehogs have started a family and we now have a family of four plus two from last year, so that’s six in a comparatively small garden. Just some well-sited Hedgehog houses (under ferns and the like), a bit of bedding (though they’ll bring their own), some holes cut through fences and gateways to allow access and nightly feeding (which does cost I’ll admit) and these lot are happy. No Hedgepigs in decline here Chris Packham 😛

General Weather Situation

Bit of a grim one for what I know is a holiday month for many of you but it’s not too bad.

So Monday starts with low pressure in charge and so we will see plenty of showers moving across the U.K and Ireland during the course of the day. Some of these will be snap showers accompanied by a rumble of thunder but most of the electrical storms went through last night. Since this is an Atlantic low pressure system, most of the rain will be tracking west and north across Connacht and Northern Ireland and across Central Scotland through the course of the day with the showers consolidating to longer spells of rain this afternoon / evening. South of this rain front across the south of Ireland and central and southern England / Wales we will see a line of showers moving across from the west of the U.K into central areas through the morning and again we may see some consolidation through the afternoon into longer spells of rain. They will be few and far between though. Northern England may just miss the bulk of the northern and southern showers later in the day. Temperature-wise, it’ll still feel pleasant so high teens to low twenties for Wales and England and down in the high teens for Ireland and Scotland with the heavier cloud base and rain. The wind will be moderate to strong and from the west / south-west.

After a cooler night than of late during which temperatures will dip down to low double figures, we will see more rain from the off across Ireland and Scotland. During Tuesday morning the bulk of this rain will be more northerly and westerly-orientated but as we go into the afternoon that rain will consolidate and shift southwards across central and southern areas of the U.K. So dry initially for central and eastern areas of the U.K and wet across Ireland, Wales, the west of the U.K and Scotland before that rain pushes east in the 2nd half of the day to cover all areas. Again breezy from the south-west with a strong to moderate wind and temperatures a couple of degrees lower for the south of the U.K, high teens and maybe just nudging into the twenties early doors before the cloud pushes in.

Onto Wednesday and mid-week beckons promising a drier day for many areas than Tuesday. With low pressure still about we will have a continuation of showers across the west of Ireland, the south-west of England, South Wales possibly as well and definitely across the north-west of England and Scotland. Some of these showers in the north will be heavy. There will be though plenty of areas starting off dry on Wednesday and with some hazy sunshine about it will be a pleasant 1st half of the day for the north of England, Midlands, central and southern England. During the afternoon though we see a familiar pattern developing with showers pushing eastwards across northern and central areas of the U.K, the same with Ireland. So a wetter 2nd half of the day is likely but as that rain moves eastwards we will see it clear the west of Ireland, Wales and The South West to give some sunny intervals to end the day. By dusk that rain should be clearing the west and central areas of Scotland and Ireland with just some showers across the east of Leinster likely.

Image courtesy of Tropicaltidbits.com

Thursday sees that low pressure exiting stage right as it moves off into Scandinavia but as you can see from the SLP graphic above, another low pressure is heading our way from, yes you’ve guessed it, The Bay of Biscay. Now currently it looks like we won’t see landfall till later on Thursday evening into the south of Ireland and The South West so Thursday could be the driest day of the week for many.  So a pleasant day beckons for the U.K and Ireland then on Thursday with lighter winds and some sunshine but we will see more in the way of cloud build from the west through the day. By Thursday night that low is projected to bring heavy rain into the south of Ireland and south / south west of England, Wales before moving north and east through the night. I think with the tightness of the isobars as well it’ll be very windy with it overnight into Friday. A bit pointless predicting wind direction because it’ll depend where you are with respect to the low pressure. Similar temperatures to the rest of the week, high teens and just nudging 20°C in the south.

Image courtesy of Meteoblue

Closing out the week on Friday and that low pressure system is projected to be right over us as the image above shows for 6 a.m. Friday morning. so a very wet day for many to close out the week as that low pressure tracks slowly north and eastwards. By lunchtime the heaviest of that rain will be over Scotland and the north of England, north of Ireland leaving behind a brighter, showery picture for central and southern regions of England, Ireland and Wales. Pretty windy as well, mainly from the south west over the U.K but Ireland will see north easterlies as they’ll be on the other side of the low pressure. (see above) Temperature-wise high teens under the rain and nudging a little higher as skies clear across the south later.

So with low pressure across the U.K at the end of the week, it’s probably not surprising that Saturday’s forecast is a tad unsettled. With the centre of the low pressure moving out into The North Sea that means the U.K and Ireland will pick up a cooler north-westerly wind and that’ll rattle in showers on Saturday. These showers and longer spells of rain will affect the north and west of England / Ireland and Scotland with Wales in the firing line as well. A bit of disagreement how far south these showers will push though so central and southern England may see less during Saturday morning with more pushing south p.m. maybe. A sunnier and warmer day for England on Sunday as more of those showers stay confined to the north and west. So continuing unsettled then for Ireland, Wales, Scotland and the north of England, particularly across westerly facing coasts.

Weather Outlook

Well after an unsettled week this week do we see a lift in the jet stream and a return to some drier, warmer, summer weather ?

Well in a word…No.

Next week doesn’t however look to start off too bad with a sunshine and showers scenario for Monday and Tuesday and some pleasantly warm temperatures. By Wednesday though the week looks to be on a downhill slide as a low pressure system is set to bring rain, some of it heavy to Ireland initially before moving eastwards to affect all areas. Thursday sees that low pressure move through but by Friday another one is on its way so become increasingly wet and windy for the end of next week / weekend. Sorry.

Agronomic Notes

Since this is the first blog of the month it is of course customary to look back on last month, July and see how it panned out ?

GDD Summary – UK Location – Thame, Oxfordshire

Looking at the GDD total for July, 381.5 is 12% lower than last year and reflects the cooler, wetter interlude we had in the last week of the month. Interestingly if we compare it to last year from an E.T and rainfall perspective in 2018 this location had 132.7mm E.T loss and 16.4mm of rainfall vs. 108.4mm E.T loss and 18.6mm rainfall in 2019.

2019 continues GDD cumulative-wise to only being a so-so year from a temperature perspective, slipping behind 2018 and as suggested last week, following a very similar pattern to 2014, specifically I think during August.

GDD / Rainfall Summary – UK Locations 

Well I am amazed to see dear old Market Harborough top out as both the warmest and wettest location in July 2019 from our limited data set. That rainfall total was helped on its way by 31.5mm on the 28th July, a day when it rained solid dawn to dusk and didn’t top 15°C. Temperature-wise we hit 36.6°C on the 25th, so we had our warmest and wettest days of July within 4 days of each other. That’s a similar pattern for other locations and marks out the end of July as a prime trigger point for Anthracnose in my books as discussed last week. When you compare the GDD for Fife with Okehampton, so our furthest north and south locations, there’s an 18% swing in temperature from south to north !

GDD / Rainfall Summary – Irish Locations 

A pretty busy Irish chart tells a number of stories ;

For some locations particularly along the east side of Ireland, July 2019 was a pretty dry month with the rain not arriving till the end of the month. Cork, Wexford, Killiney, Dublin and Donabate were all around 30 – 40mm of rainfall for the month. Across the west of Ireland the stats tell a familiar story with Valentia and Claremorris the two wettest locations. Still love Mayo though but then I don’t have to live there and put up with the rain I know. Growth-wise the results were pretty consistent across Ireland with very little variation between sites but I think in some Irish locations during July 2019, it would have been moisture (or lack of it) rather than temperature that was a growth-limiting factor. Interestingly if you compare the average GDD of the U.K locations with the average of the Irish there’s a near 20% reduction in temperature across the Irish Sea.

Using GDD Data – PGR Applications

Now we know the Americans like to do things differently and they calculate their GDD stats using a base temperature of 0°C rather than the 6°C that I have utilised since I began working with GDD.

Why the difference ?

Well I can’t speak from their perspective but my thinking is this is supposed to be a growth model and in my experience foliar growth of grass doesn’t take place below 6°C so why count it in a model ? Anyway that’s not the point of this section of the blog.

Every summer I get feedback from good Superintendents on the efficacy or rather inefficacy of their Trinexapac-ethyl applications (TE) PGR applications. The contention is that they aren’t providing the suppression they did in past years. Now I’ve heard this feedback from Superintendents from the other side of the pond when sitting in GCSAA classes and it goes along the line that applying the same rate of TE at the same frequency doesn’t appear to give the same growth suppression.

There are lots of variables involved here because we know from the excellent article “Avoiding the rebound”  (read it here) that TE has a finite life within the grass plant and breaks down faster at higher temperatures. So during the warmer days of summer we have to be careful on our application frequencies. Now the data from the article talks about applying every 200GDD to bentgrass greens calculating the GDD figure using a base of 0°C rather than the 6°C. If you do the maths that correlates closely with applying every 130GDD using a base temperature of 6°C.

So I thought I’d pick 3 locations and run the maths working on applying every 130GDD during July 2019 and starting on July 1st.

Here’s how the data looks…

 

So for the Cork location, if I applied a PGR on the 1st July and worked on re-applying every 130GDD, the next application would be required 13 days later and the next application only 12 after that. For Northampton, the stats are slightly different with the 1st application lasting 12 days and the next one only 11 days. Finally for Fife, the first application lasts 14 days and the next one again only 11 days.

So if you’re applying a PGR every 14 days the potential duration of rebound is ;

Cork 

1st application – 1 day  / 2nd application – 2 days

Northampton

1st application – 2 days  / 2nd application – 3 days

Fife

1st application – 0 days  / 2nd application – 3 days

What I mean by potential duration of rebound of say 3 days is that the PGR will have reached the end of its longevity after 11 days and won’t be re-applied again until day 14, so there are 3 days when the grass plant is rebounding from the effect of the PGR. As the paper comments, the amount of rebound will be proportional to the amount of regulation so we theoretically will see a growth flush for 3 days before the plant is regulated again.

I mentioned there are lots of variables and one of them is surely the amount of growth you are regulating. Now this is more accurately described by Growth Potential rather than GDD because the formula for G.P as we know has a ‘top out’ optimum temperature above which grass growth declines rather than increases.

So lets look at the pattern of growth during July 2019 from a Growth Potential perspective ;

You can see the big dip at the end of the month (25th July) when we hit those really high temperatures decreasing growth. That said, apart from that dip, conditions from a purely temperature perspective were near optimum for growth for most of the month, so we know the PGR was having to regulate significant growth.

So here’s a question, when we look at using a PGR from an application rate and frequency perspective do we take into account the amount of growth we are trying to regulate ?

Are PGR’s like TE becoming less effective or is the growth rate or type of growth less able to be regulated by the PGR itself ?

Of course temperature isn’t the only growth-limiting factor, moisture is one as well but I’m assuming we are irrigating and monitoring the water content of the rootzone accordingly 🙂

Are PGR’s applying a selection pressure to our surfaces ?

I’ve talked about this one before but there’s no harm in re-visiting it in my mind.

So let’s assume our greens are bent and poa annua and we are maybe overseeding with ryegrass (perish the thought from some quarters but it’s a fact of modern day greenkeeping)

Now we know TE works differentially across those 3 grass species, i.e. it doesn’t regulate them all to the same degree with Poa annua the most regulated, then bentgrass and then ryegrass. So in my mind it follows that surely the PGR will encourage the less regulated species to out-grow the most regulated ? So Poa annua would be out-competed by bentgrass and ryegrass in the above example.

On a pure Poa green we know we have lots of different biotypes of Poa annua across a sward, you can see that clearly at seedhead time. So I think it’s pretty safe to assume we would have the same differential response to a PGR application across a Poa green. That is some of the Poa biotypes would be more regulated than others and therefore out-competed ? It follows then that we would eventually move to a sward where the dominant Poa annua biotype was less regulated by a PGR application. So are we seeing selection pressure being applied by a PGR and is that one of the reasons why the same rate and frequency of application is less effective ?

Dovetail that in with the rebound effect and potentially greater growth from the grass plant to regulate in the first place and it might explain why a PGR isn’t as effective as it once was maybe ?

Food for thought ?

I keep remembering the words of that song…”Things that make you go hmmm”

You get a lot of that in this job don’t you ? 🙂

All the best for the coming week.

Mark Hunt