Happy 4th of July 🙂
A late blog this week because I’ve been up at the European Turfgrass Society (ETS) Conference since Sunday. This year it was held in Manchester and they had some really good Turfgrass researchers from around Europe and the U.S sharing their findings across a number of subject areas. (You can see the program from this weeks event to get a flavour of the type of talks here)
Some of the gems of wisdom I gleaned I’ll discuss in next week’s blog as they are both relevant to current conditions and also interesting to boot. I presented a paper on the role of phosphite as this is a contentious subject at present. Fortunately our company is involved in some pretty high level research in this area which I hope will benefit not just the U.K, but European and possibly U.S Turfgrass industries going forward. Won’t be putting it on the blog though because of the Rank Xerox brigade 😛
Now you don’t need to be a rocket scientist to know that June 2018 checked out as a very dry month and for some areas, the driest since records began in 1901. We had 1.8mm here in Market Harborough and I reckon that’s par for the course not just here in Central England but also in Ireland and Wales as well. Scotland started dry and warm, had a wet middle of the month and has then been dry for the last 10-14 days.
In terms of meaningful rain, our last here was on the 30th of May, so that’s well over a month without rain. Some areas of the continent are just as dry as we are…..
Now having said that as I type this blog I can reveal IT IS RAINING SOMEWHERE IN THE U.K AS I TYPE ! (Shock horror)
As you can see Avon and some parts of South Wales extending along the M4 are getting appreciable rain and some other storms are kicking off close to the M1 (Please, please come to Market Harborough 🙂 Footnote – They bloody didn’t ).
I reckon the latter have been created by hot air updrafts emanating from the large distribution warehouses around Milton Keynes and Rugby.
It’s not just the long run of hot days that has been unusual, nor the lack of rain, it is the nature of the E.T loss in June that has caught my eye. We have had a predominantly north-east wind in place for 2-3 weeks and that has meant it has remained windy not just through the day but overnight as well. This has really ramped up the 24hr E.T figures and I’ll be speaking about this later in the blog.
General Weather Situation
So I’ll start my forecast from Wednesday afternoon because that’s when I’m putting this blog together. As mentioned earlier we have some rain around across The South West and South Wales and also some cloud building across North London and Essex. Some of this cloud could thicken to give localised rain don’t you know but where and when is a job for your radar app and not my forecast. Elsewhere it’s another day in paradise with hot, bright sunshine, a little cloud cover and temperatures climbing into the upper 20’s across the U.K, with Scotland and Ireland on the low side of twenty degrees. (Lucky you) A bit more in the way of hazy cloud around in places which will just make things a little more bearable and light winds as well compared to late.
Onto Thursday and that cloud cover may well remain across Ireland, Scotland, The Lakes and the south and east of England. In places you’ll start and remain bright on Thursday as that cloud cover burns off but it wouldn’t surprise me if for the second day running we see some rain showers bubble up during the early afternoon across The South West, possibly South Wales and the south of England. The reason for this is a low pressure across The Bay of Biscay is feeding some moisture into the hot air system but sadly it’s mainly confined to the south of the U.K. Similar temperatures to Wednesday really with mid to high twenties depending on cloud cover for England and Wales and a tad lower for Ireland and Scotland. We may also see the wind swing round to the north.
Closing out a short week (or a long one for me as it started on Sunday) we do it all again on Friday with plenty of cloud starting the day and in places this may be reluctant to burn off till the afternoon. I think we are less likely to see rain bubble up down south on Friday but you never know. Similar temperatures again for Friday, low to high twenties depending on where you’re located and a freshening north-westerly wind likely to ramp up the E.T again.
For the weekend I think we will see the heat start to build again towards the high twenties and even I think pushing into the low thirties on Sunday possibly in places. We will also see a return of that north-east / east wind I am afraid. Hopefully our Celtish contingent will excuse a slightly partisan reference to the England football team to whom I wish all the best to on Saturday. Nice to see some passion in our game for once. That said, the standard of play acting is shameful from some of the teams, come to a road, BSB, WSB or MotoGP race lads and man up is all I can say 🙂
Now I confidently predict that this part of the blog will be receiving more scrutiny than usual this week as we enter our 6th week without rain (and longer than that in Scandinavia)
So next week looks like starting off very similar to how the week ended with long spells of bright, sunny weather and high temperatures. Less in the way of cloud cover compared to the end of the week possibly and depending on who you believe, that’s the way we look set to stay with a blocking high pressure in The Atlantic. I say this because 2 weather models beg to differ from this continued drought prognosis.
Unisys shows a low pressure forming south-east of the U.K around this time next week and then slowly pushing north and east to bring cooler and perhaps unsettled conditions next weekend. Now it is and should be viewed with a big ‘IF’ because we had the same this time last week and the low has never moved northwards rather it has remained in The Bay of Biscay. Metman James is erring on the side of continual blocking and that’s probably where the smart money resides but I like to give a bit of hope to us all that may be struggling with poor irrigation systems and the highest, prolonged E.T stress we have had for a good few years.
So maybe just maybe we will see a change towards the end of next week….I will do a mini-blog at the end of the week if this signal remains in situ and if it doesn’t then I’ll revisit my hunch next Monday as per usual with a despondent shrug 🙁
Since this is the first blog of July we can take a long, hard look back at June 2018 and crunch some pretty dry and parched weather stats.
Thanks to Wendy for taking the time now she’s back from yet another holiday (arf arf) to compile this info. Thanks also to the usual band of contributors, cheers everyone 🙂
GDD Comparison – U.K Location – Thame
This is kind of when recording and comparing historical weather data really comes in handy because I was staring at June 2017’s GDD monthly figure of 329.5 and trying to think back to last June and whether it was hot or not ?
I then remembered we had a particularly hot spell on the run up to Wimbledon (Good luck lads for the tournament by the way) when temperatures soared into the low thirties. So June 2018 isn’t the highest monthly GDD we have measured at 314, but it comes in just a tad behind 2017 and maybe it is significant that the last 2 years have been the highest ever ???
Cumulatively we are catching up fast after our cold, wet and tardy start to 2018…wet ? you remember wet don’t you ? We have now overtaken all the previous SSW-event years and I wonder where we will be in a months time ?
GDD & Rainfall Comparison – U.K Locations
Aside from a smidge more rain for Bristol (most of which fell on the 2nd of June !), you can see how dry we are with 2 locations recording no rainfall at all ! That said I reckon half of my monthly total was courtesy of the sprinkler irrigating my Netatmo Rain Gauge !!!! The high GDD figure for my location comes down to sensor location in that it picks up the afternoon sun directly so I get some pretty elevated afternoon temperatures !
What these stats don’t show is the other side of the coin for a hot, dry June and that is extended plant stress due to consistently high E.T.
GDD & Rainfall Comparison – Irish Locations
So we see Ireland comes in with a very consistent GDD figure across all locations, except Limerick which is higher than the average. The consistency of measurement points to the stability of the weather situation that has affected not just Ireland, but the U.K and Continent as well. Rainfall-wise we can see the west of Ireland has had more rain than the east, as per usual, but even for the west these figures are pretty low and reflect precious little significant rain in June. What I mean by that is that most of the rain in the Irish stats occurred either at the beginning of the month of June for the east of Ireland (literally the 1st day of June was the last rainfall for some of the locations !) or the amount of rain that fell in the middle of June across the west was compromised very swiftly by E.T rates. (evaporated off before it wetted the ground)
June 2018 vs. June 2017 – Focussing on Evapotranspiration (E.T) and Rainfall
So I am using data from The Oxfordshire to compare June this year with last year and it makes for interesting reading. First off let us define E.T as the amount of water lost from the grass plant by transpiration (through the stomatal pores) combined with water lost from the soil by evaporation.
Now E.T in weather stations is usually calculated using a complicated equation known as the Penman-Monteith Model (PM). I’m not going to go into this in too much detail but the equation takes into account a number of factors to calculate the potential water loss from the plant and soil surface but of course it is an estimation. There are a lot of variables when it comes to calculating actual E.T (E.Ta) using the Penman-Monteith model and normally you have to multiply the calculated value by a crop coefficient (Kc). This is because the model assumes the crop has a height of 12cm and I think we’d all agree that we aren’t cutting quite that high 🙂
To look at it very simplistically, the PM model tends to over-calculate water loss by E.T and so if you irrigated to replace the water loss calculated by the PM model, you’d have a saturated surface. So the common practice is to water at a % of daily E.T. In my experience I found that irrigating to replace 60% of calculated E.T loss was a good starting point and that if this was reduced to 40%, I saw plant stress symptoms develop. Now of course things have moved on at a pace when it comes to irrigation because we know most end-users only apply a % of their requirements through mains irrigation and then hand water to supply the rest on areas that are known to need it. How do you know where those areas are and how dry they are ? Well the increasingly popular method is to use a moisture meter to identify dry areas and evaluate irrigation efficiency (hand watering or mains applied) Moisture meters really come into their own at times like these.
So let’s look at the stats for June 2018 vs. 2017 and the irony is that the total monthly water loss by E.T was actually identical at 111mm in 2018 and 2017, uncanny but that’s where the similarities end.
The rainfall totals were different with 39.2mm falling in June 2017 vs. 2.4mm in June 2018.
So in June 2017 (above) we started the month with a net deficit of moisture but rainfall on the 5th, 6th and 7th of June took the soil almost back to a neutral level in terms of moisture levels. Thereafter the soil dried out progressively with the next significant rainfall on the 28th June halting the process. Now of course I’m simplifying the situation because I’m assuming I start the month with neither a soil moisture deficit or surplus. (Bear with me though)
By the end of June 2017 we had a theoretical deficit of -72.4mm.
Now let’s look at June 2018 at the same location…
You can see a clear difference with an increasing daily soil moisture deficit from the 1st of June right through to the 30th June and a total figure of -104mm.
So if we were irrigating to replace 60% of E.T in June 2017, we would require 43.4mm of water vs. 62.4mm in June 2018, that’s 43% more water.
Longevity of E.T stress
There’s another more significant difference though and it relates to the longevity of continual E.T pressure on the grass plant.
In 2017, we can see that continual E.T pressure didn’t really start until the 11th of June and with the arrival of rain on the 28th June, this process was halted. So the longest period of continual E.T stress in June 2017 was 18 days.
Compare that with June 2018, when the continual E.T pressure started at this location on the 1st of June and continued throughout the month unchecked, so that’s 30 days of continual E.T pressure and of course we know that the process is still ongoing in July.
So both months might have had the same E.T level but the result in terms of higher levels of plant stress in 2018 are certain to be more severe in my books. This is due to the longevity of the stress period and the fact that there’s been no respite for the plant.
Consequences of continual high E.T stress
I believe that we will see more disease development on our turf surfaces as a result of these elevated levels of continual E.T stress but in general I don’t think we will see this till the arrival of rainfall and increased atmospheric humidity.
Principal among those diseases will be Anthracnose and Dollar Spot because they’re stress-related.
Use of PGR’s during stress periods
I get a lot of questions on this front when conditions are as they are so I used my ETS attendance to canvas opinion with the guys that have looked at this. The consensus is that continual applications of Trinexapac-ethyl at the label or sub-label rate are on balance positive with respect to grass plant health. In particular the use of ‘little but often’ TE (and it would have to be little and often with current temperatures to avoid the rebound) has been shown to decrease plant moisture loss and thereby lower stress. It’s logical that if you decrease leaf shoot production then you decrease net water use by the plant. There’s also the potential to increase plant rooting by taking the emphasis off top growth. I’m not particularly sold on this one, never have been but maybe during certain conditions (high E.T stress) the effects are more obvious. Now of course we come to the age-old question of rate and I know there’s plenty of viewpoints on this one. We know Poa annua is one of the most susceptible species to this type of stress (particularly the annual biotype) and the most-affected by TE. So using a higher-than label rate of TE during drought stressed conditions is likely to increase Poa annua stress. Fine if that’s your objective, not so fine if it isn’t.
I believe that the use of a combination of seaweed and humic acid at this time of year is beneficial to plant health, particularly when the plant is under stress, be it abiotic or biotic.
It is quite likely that use of these products outside of stress periods imparts less benefits but I think they do come into their own when we are faced with situations like the above. The objective is keeping plant health in balance with nutrition and not producing too weak or too lush a grass plant. It is though a tricky balance.
How high is our E.T at the moment and how does it compare to the United States for instance ?
One of the researchers presenting at the ETS was based in California and some of you will know they are enduring an extended drought scenario. In his own words “Our drought is bigger than your drought” 🙂
The researcher put up some weather data that showed their E.T losses per month can be as high as 200-250mm at their peak, that’s an average of 6.5 – 8mm per day !
So where are we in the pecking order of E.T ?
Well I borrowed this Twitter snippet from the venerable Ian Kinley @ Royal Porthcawl G.C.
You can see his weather station is recording a 24hr E.T of 7.64mm, so we are right up there currently. Any advance of 7.64mm ?
I should also point out that minutes after posting this clip they duly picked up a nice and steady 3mm of rainfall (let the slagging begin)
Ok that’s it for this week, sorry for the lateness in the day and week for sending this out. I’m off for a nice walk around a reservoir (possibly with a rod and bag) on the look out for some late-rising Trout 🙂
All the best.