After a cool week last week and a chilly weekend (particularly Saturday), we have a continuation of that cool theme for most of this week as a cold low sits south-east of Iceland and funnels cold air down into a trough in the jet stream . Rainfall is likely to be on the low side and more Ireland / Scotland orientated, so a dry one as well. It’s been a topsy-turvy month really, with 2 distinct growth spurts, followed by cooling interludes and now we have a week of the same, with cool / cold nights and mild (ish) days. Still nature is playing catch up and I was delighted to see my first Swifts yesterday, plus watch an Osprey take a lovely trout in front of me at Eyebrook reservoir, bit cheeky really of him as he doesn’t even pay for a season ticket 🙂 I reckon we are still a month behind from a nature perspective and when you see the GDD data for April, we are still playing catch up from a grass-growth perspective as well, big-time. This is causing some issues related to differential growth on greens, between different biotypes of Poa and with bentgrass as well and these will continue this week. Poa seedhead flush ?, I reckon the 2nd week of May looks a likely candidate, that’s 2 weeks later than normal.
General Weather Situation
Monday sees some overnight rain clearing the south-east of England, but after a bright, cool start in The Midlands and south of England, cloud cover soon builds as a band of rain showers pushes down over Ireland and Scotland, dissipating as it moves south, so sunshine and showers the order of the day, pushed along on a cool, north-westerly wind. As that cloud cover thins later, temperatures are likely to drop and that may give a ground frost overnight. Ground frost is likely to be a continued threat for most of this week in Scotland and England particularly by the way. Moving into Tuesday and those brisk winds lighten, but swing round to the north, so continuing cool, still though a largely dry, sunny day, after a cool start, with temperatures pushing into low double figures day time. Wednesday sees light winds and a continuation of the dry, cold start theme, with again a risk of ground frost, particularly for Scotland and parts of England, but a dry picture for the UK and Ireland. Later on a rain front pushes into north-west Connacht and then proceeds to move south-east across Ireland through the day.This rain is due to reach Scotland later on Thursday morning and then slowly sink south into the borders. Elsewhere the outlook is dry, cool, but with light winds, it’ll feel warm in the sunshine. That rain band intensifies into Friday over Ireland and Scotland, and as it does so, it begins to move south, reaching Wales and the north of England by Friday afternoon and then pushing southwards into The Midlands, along with cool north-west winds. The cloud cover during Thursday and Friday means a much reduced risk of frosts. so there’s a positive flip to the rain. So a slightly wet end to the week for southern England as that rain band passes through during Friday evening. Saturday starts off with showers and a cool northerly wind, but later into Saturday evening, the temperatures will begin to rise as an Atlantic high pressure begins to exert its influence for the 2nd part of the Bank Holiday weekend. Sunday and Monday for the U.K look like being dry, warm, sunny days, with temperatures projected to nudge into the 20’s. Ireland will have more cloud cover later on Sunday, with rain projected to push into Munster overnight into Monday.
As per last week, this is still without the Unisys factor 🙁
The week commencing Monday 6th May sees high pressure firmly in charge, so light winds, cool nights, dropping to 4-5°C, but temperatures pushing to the high teens / low twenties for the southern half of the U.K. The west and north will be cooler for the 1st part of the week, so I’d take 4-5°C off the above, but from Wednesday, temperatures will climb here as well. It will remain dry, with only the only rain incursion being at the start of the week into Ireland. Elsewhere, there’s no rain forecast.
We have some tricky growing conditions at present, with the usual dichotomy related to outfield and fine turf growth rates i.e outfield turf is growing pretty well at present provided moisture is present, though it should be still under control as soil temperatures are only hovering at high single figures.
Greens / fine turf growth is another matter with Poa annua in particular proving a reluctant customer in terms of uniform growth. I’m getting some feedback where the grass sward across a green is showing multiple growth rates, from dark green and vigorous, to yellow and dormant. The cooler the regional area, the more pronounced this effect is and it’s particularly evident where there is a mixture of Poa biotypes present across a green. This is to be expected because we see the same when we talk about purpling across a green, we don’t see an even purple discolouration, we see patches across a green depending on the distribution of Poa biotypes, specifically ones that are growing at low temperatures and ones that aren’t. This has implications not just for growth but also for nutrient uptake from a fertiliser perspective because the Poa that is growing better at low air / soil temperatures will uptake nutrient, whereas the Poa that is dormant will not, so sometimes fertilisation will make the effect worse, i.e exasapate it. One of the key factors related to the appearance of differential growth appears to be the distribution of the tight, perennial Poa across a managed turf surface, because this appears to be the last biotype to start growing, temperature-wise.
I’ve talked about the lack of growth potential this year and recently showed some growth-degree-day data, but reading Karl Danneberger’s articles on the subject, he inteprets the calculation slightly differently, so we’ve amended ours to correspond with his and you can see from the charts below, the lack of growth potential both this spring cumulatively and even this month (the data is up to the 22nd April) is quite staggering.
From a cumulative growth perspective and starting from January 1st this year, we’re tracking at 50% of a normal year and 33% of a strong growing year, in other words, we’re coming from a long way back. I think we’ll probably just crack 100-105 cumulative GDD by the end of April 2013, but that’s still 40% lower than the last poor spring (2010) and 66% of a good spring (2011). One last point, the GDD calculation relates to maximum and minimum air temperature and I know the west of the U.K and Ireland has been a good bit cooler than the central UK region (where our data is collated from), so expect the lack of growth differential to be even lower.
Looking at the forecast for this week and the likely one for next, we appear to be going dry in the main part and so liquid / water-soluble fertilisation is going to be the order of the day as opposed to granular. I’d be looking at the usual suspects from an N-Source perspective, i.e ammonium sulphate, nitrate, potassium nitrate and I’d definitely be using iron to mask the differential growth response noted above. A couple of people have asked me about PGR usage, i.e trinexapac-ethyl and in my mind, on greens / fine turf, it’s too early yet. On outfield turf, that’s another matter, because if you have good coverage and just want to peg things back before the bank holiday, then it makes sense to do so.
My last point concerns Leatherjackets, well there’s a hell of alot about at present and their presence is given away by the chamfered, countersunk appearance of a feeding hole across a sward. In terms of treatment, as it is dry for many places, I’d be using a penetrant (registered adjuvant obviously) to get the Chlorpyrifos down where you need it to be. In the picture below, the grub was sitting about 40mm below the surface of this particular feeding hole.
L8trs (teenage text speak for that’s all for now apparently!)