Hi All,

Bit later in the week than usual I know, but up with the lark at 5 a.m. Monday morning and I was already 2 Costa’s shy to the wind by 9.30 a.m., sitting in the sunshine on the M25, what a rad-man lifestyle I live! didn’t finish this blog post until late on Monday night and didn’t think it sociable to publish it at 11 p.m. so Tuesday morning it is….

Hmmm, the first part of this week looks not great really, as we’re being paid a visit by a cool, Atlantic low pressure system, especially Tuesday and Wednesday, with a chunk of rain on the way for a number of us, though strange as it may seem to some, very welcome in the central and eastern parts of the country, where rainfall has been hard to come by of late… So let’s put some detail on it…

General Weather Situation

Tuesday sees two separate rain fronts pushing into the U.K and Ireland, the first reaches the west coast of Scotland early doors, the second, reaches the south-west of England / Wale, mid-morning and tracks its way diagonally (/) along the M5 towards The Midlands, pushing through to reach the east of England later in the day. The extreme south-east and the area north of say,The Humber, should escape the worst of this rain, but for areas in the firing line, it’s looking like a minimum of 10-12mm is on the cards (more – 50% – for the south-west I’m sorry to say). The rain will be pushed along on westerly winds and they’ll be keeping temperatures down to low double figures through the day. Over night the rain will push into the south-east and east of the country in earnest, so heavy rain for the early hours on Wednesday in these areas . Ireland should miss the worst on Tuesday / Wednesday, pushed along by those westerly winds and instead have a mixture of sunshine and blustery showers. Showery is the picture for Wednesday after that heavier rain clears the east of the country. As skies clear, temperatures will drop on Tuesday and Wednesday night, so a chilly start for many compared to the double-figure nights of late. Thursday will start off dry for Ireland and the UK, but showers will soon bubble up in the west of Ireland and push easterly across the country. The winds though will be much lighter than of later and possibly southerly, though not warm, southerly by any stretch of the imagination. The same weather pattern is true for the U.K with showers bubbling up later in the morning / early afternoon Thursday, but much lighter rain and winds than Tuesday or Wednesday. Friday sees a re-run of Thursday with a showery pattern of weather for Ireland and the U.K, light winds, but remaining cool with low double figure, daytime temperatures. The weekend is looking slightly better, with a dry day in prospect for Saturday, though again there is still a chance of light showers for Ireland, Wales and the west of the U.K p.m. Sunday is looking the reverse with a drier day in prospect for Ireland and the west, but after a dry start for the east, a significant heavy rain front is projected to push across from the continent into the east / south-east of England / The Midlands during Sunday morning and at this stage, it could well bring an 15-25mm of rain to these areas, so not good at all. By the time the rain has reached more central areas, it will give lower, but still significant amounts of rainfall by late morning / early afternoon, so a wet 2nd half of the day here. For the west of the U.K / Ireland, it’ll stay dry most of the day, with no risk of rain, but it’ll still be on the cool side I’m afraid.

Weather Outlook

Still no Unisys solution, but we’re working on it and the GFS models I’m trialing correctly forecast last week’s Bank Holiday weather and the rainfall for Tuesday / Wednesday this week, so all is not lost 🙂 After the potentially heavy rain for some areas on Sunday,  Monday and Tuesday are looking much drier and hopefully temperatures will also pick up in the lighter winds for the early part of the week as a high pressure tries to nudge its way in. At the moment, this looks like stalling after mid-week, so dropping back cool again, but hopefully staying mainly dry. Looking to the very end of next week, we may see that high pressure push in again, so who knows, a nice end to next week ?

Agronomics Notes

Ok, there’s lots to talk about this week, so I’ll try and make it interesting 🙂

Poa seeding

The hot Bank Holiday weather in the U.K (cooler in Ireland I know) triggered the beginning of the Poa seed head flush, but it’s only the beginning because as we can see from this pic, it’s the coarser, annual biotype that’s seeding first, whilst the finer perennial biotype, which produces much less seed heads will follow in due course. If we look at the GDD data from The Oxfordshire, it suggests that the annual biotype began seeding after the cumulative GDD data measured from Jan 1st reached 154. Obviously temperature isn’t the only influencing factor, but this sets a line in the sand, data-wise for the future.

GDD and shade

Now a word of caution, it’s clear from my initial work (ably aided and abetted by the increasingly-proficient Wendy, whose getting a dab hand at crunching this data :)) on GDD data, that there exists great variability from course to course and within 18 greens on a course. If, for instance, you take a tree-lined course, shade plays a bigger part, particularly early in the year when the height of the sun is lower on the horizon. (as this pic shows with the mid-winter path of the sun shown in blue and the early spring path of the sun shown in yellow).

In this scenario, early in the year, because the sun doesn’t clear the tree line, the turf doesn’t warm up as much during the day and consequently drops to a lower temperature at night, so the growth potential is much lower than a more open site. This fact is amply illustrated in the GDD data from 2 sites shown below, the first an open course (minimal shade) sitting at 71m above sea level (asl) vs. a heavily tree-lined course, less than 20 miles away, but crucially also sitting at a greater elevation – 166m asl. Comparing the GDD figures for January, one can see that the tree-lined site had only 25% of the growth potential of the more open site, so when early January was mild, the more open site benefited, whilst the tree lined site did not. The same would be true when you compare greens on the same golf course in an open and shaded perspective.  This has both growth and aeration implications, i.e. you could imagine a scenario where early (January) aeration would work on the open site / greens, but recovery would be much slower on the tree-lined, woodland site / greens.

Soil Temperature / Night Temperature / Growth Potential

You can see why the GDD data is so useful when you look at the graph below of the first 8 days of May. If we just focused on soil temperature alone, you’d say well no great shakes there because it’s pretty consistent over this period, so growth should be as well, but this isn’t the case. If you look at the GDD figures you’ll see that they are pretty low and that’s because the night temperatures were low, so regardless of what the soil temperature reached during the warm part of the day, growth wasn’t forthcoming because of low night temperatures.

You can also see the effect of milder night temperatures on growth potential. On the 8th May, the night temperature was mild (11°C), and the GDD suddenly shoots up to 10.5 and produces a flush of growth on all areas (temporarily).

 E.T / Irrigation Requirement

Those first 8 days of May also highlighted that perennial issue, to water when it is cold at night or not.

Quite simply the logic behind not watering is flawed. If you look at the graph above, on a open site like The Oxfordshire, the total E.T. loss for the first 8 days was 26.4mm and during that same period, only 0.8mm of rain fell, so that leaves a soil moisture deficit of 25.6mm. Working on replacing 60% of that to keep a healthy plant, we would have needed to apply around about 15mm of irrigation over that period. So by not watering, you effectively stop the plant growing, particularly perennial Poa. The argument behind not irrigating with cold water at night is that it will cool the soil down and stop growth. Well you’ve done that anyway because of E.T loss. So the rub is to replace moisture during these periods with light irrigation patterns to wet the top part of the profile, because this is the part that’s drying out. Of course, The Oxfordshire is an extreme example, the E.T loss if high because it’s an open site and the rootzone is USGA-spec, it also doesn’t tend to receive high levels of rainfall. Now your situations will be different, you may have less E.T loss, more rainfall, but remember, by under-irrigating you reduce the soil moisture level to a point where the plant is unable to uptake nutrients, so even if you’ve fertilised, you won’t see the benefit if you’ve under-irrigated / dried the profile down too much.

Nutrition / Spray Windows

If you’re in a situation where you’re still experiencing differential growth and therefore an uneven surface and you want to get things moving, so you can verticut, topdress (and get growth through it) and maybe reduce the cutting height, then for the next 7 days, a low temperature-available, granular fertiliser is the way to go. This is because night and day temperatures will be cool and we’re due for plenty of rain, so granular’s will work best until the weather settles down.

If you’re looking to spray PGR (:)), selective herbicides, etc I’d personally wait till this rain front has moved through and either take a chance towards the end of this week or the beginning of next, after Sundays projected rainfall.

Ok, back to the grind, all the best

Mark Hunt