As I look out of the window we have light rain here, the latest addition from a low pressure system that pushed in at the back end of last week and gave rain over the weekend for many parts. If you’re off on your hols, don’t panic !, the week ahead looks dry in the main with isolated showers, mainly for the west and north, continuing warm, with heat building at the end of the week, as high pressure exerts itself again.
General Weather Situation
As discussed above, that rain will be heavy today for the west coast of the U.K before moving north diagonally (/) across the country with only the south-east remaining dry. Early afternoon could see some particularly heavy rain for mid-Wales and the north of England (Leeds / Manchester area), with the rain intensifying in this area through the evening, bringing possible flooding. Elsewhere, the rain will linger on in most places through the day, pushed along by a blustery south wind, but Ireland looks set to have a dry one to start the week, as does the south-east of England. For Tuesday, that rain should clear the bulk of the U.K to leave a dull, cloudy start for most areas, but with pleasant temperatures. During the morning, a rain front is set to push into west Munster and Connacht and move eastwards, intensifying as it does so, so rain for Ireland on Tuesday. Early / mid-afternoon, part of this rain front reaches the south-west of England and begins a slow movement, north and east, up the M5 as usual, but I don’t see amounts as heavy. Winds will be light for Tuesday.
For Wednesday we have a change in the wind direction, from south to north-east and that’ll push rain into Scotland, Leinster and northern England during the morning, sinking south to affect the west coast of England and Wales through the day. Further east will stay dry, with temperatures in the high teens / low twenties and plenty of cloud cover. Thursday sees a cloudy start for many, but it looks to stay pretty dry through the day, with hazy sunshine breaking through. Later in the day, a weak rain front is projected to push into west Connacht, Munster, but it shouldn’t amount to much. There will still be the chance of showers over the north Midlands / Wales, but again, they should be light in nature. The wind should swing round again to the west on Thursday bringing warmer temperatures, so all in all, not a bad day. For Friday, we have a cloudy day on the whole, with hazy sunshine and a scattering of showers over Ireland and north-west England, possibly pushing down into The Midlands later in the afternoon, but again, these will be light and intermittent in nature. Winds will be moderate and westerly for the end of the week and again temperatures will be low twenties, so not bad really.
The weekend looks pretty good at this stage, with temperatures pushing up into the mid-twenties on Saturday / Sunday and after a dull start, cloud will break through to give a lovely day on Saturday for all areas of the U.K and Ireland. Sunday looks similar, with just the chance of some rain / thunderstorms in the south-east corner of the U.K.
Next week looks like being a week of two halves, with the early part of the week continuing the pattern of the weekend, but by Tuesday a new low pressure system is set to push in and bring cooler temperatures and rain across the U.K and Ireland, which will carry on into Wednesday, before clearing to leave a settled, warmer picture for the end of next week.
July posted the highest growth potential figure in terms of GDD for the last 4 years, but of course we have to understand the limitations of this model. Firstly, there must be an upper limit on growth potential because we know at high temperatures, grass species slow down their rate of growth in order to conserve water and Poa annua is one of the first to dip out in this respect. Secondly, although temperatures may be conducive to growth, other factors, such as water / E.T may be growth-limiting and we certainly saw that during July with some extremely high E.T figures (more on this later). As usual, these graphs are available for download, you can access the monthly GDD graph here and the cumulative one, here.
It is interesting to reflect on the fact that if you look at the cumulative GDD data, we still haven’t caught up with prior years, that’s the effect of the long, cold winter.
Despite the limitations of the model, we can see however that once we have a GDD figure>10, the potential for a growth flush is there. Looking at data from the last week of July, we can see high GDD figures AND rainfall and this has led to a growth flush over the last week or so in areas where you have received the rain.
As a point of interest, I measured the pH and nitrogen content of the rain that fell at the end of July and for every inch of rainfall, we received about 0.6kg / N/ hectare, with the rain falling at a pH of between 6.3 and 6.5, this is normal and will have helped this flush along to a small degree.
Over the last 2 blogs I’ve been sounding a warning about Anthracnose Foliar Blight after the high temperatures and stress of July and indeed last week I saw and heard of alot of Foliar Blight activity. Areas to keep an eye on are mounds, ridges, clean-up strips and walk-on / walk-off sections of the green. Although the damage from this disease can be pretty aggressive / disruptive, it is however one that can be recovered from pretty quickly because the affected grass is usually (but not always) Poa annua and it has a fantastic ability to survive.
Poa has its drawbacks as we all know, but it also has many positives as a grass plant and one of them is its recuperative ability. In the case of root damage by diseases like Take-all and Anthracnose, I have often observed the damaged plant initiating new root development from the base of the crown. So when you’re looking at affected plants with that tell-tale yellow basal leaf, gently pluck them from the sward, strip away the leaves and look at the crown of the plant. If it is white and healthy, the chance is that the plant will recover provided you make sure that the odds are tipped in its favour. So don’t put it under stress, maximise moisture availability and make sure nitrogen is forthcoming, in light, regular applications.
Research in the U.S found that topdressing increased the recovery potential from Anthracnose-affected areas, so light aeration and topdressing will certainly help things along for sure.
Continuing on the theme of disease activity, the high temperatures and humidity experienced of late, followed by rainfall in some (but not all) areas has kicked off some Rhizoctonia diseases, particularly Waitea Patch, which closely resembles Superficial Fairy Rings (which are also doing the rounds at present) in terms of its appearance in turf. I’ve talked about this before but the main way to tell if you’re dealing with Waitea is to take a core from the affected area and have a sniff. If you smell a musty, mushroomy smell, the chances are it is a Fairy Ring associated-disease, if you can’t, then it’s quite possibly Waitea. Treatment is with the same active (Azoxystrobin), but because Waitea is surface active, you don’t want to drench the product through into the rootzone with a soil surfactant and that’s key to getting a good result.
Pearlwort (Sagina procumbens)
Quite a lot of this around at present as well and not always manifesting itself in such an obvious manner as shown above. Often you see small indistinct pale green / yellow patches amongst the sward and on inspection it looks like Poa annua var reptans, because of its very tight, bunch-like, growth habit. The quick and easy way to tell is either to look through a scope at low power resolution or failing that, take a small plug and grow it up in a pot. With the shackles of low cutting height removed, you’ll soon see the characteristic flowerheads.
Talking of weeds, grass isn’t the only thing bouncing back from the dry, hot period, there are a lot of weeds visible now so it’s an excellent time to treat with a selective herbicide.
A good number of you have been asking about E.T rates and how June and July faired in terms of E.T, rainfall and hence grass stress. The ever-efficient Wendy has put these together in graph form available for download here for the daily data and here for the monthly data. The daily data graph for June / July is too small to show here within the format of Wordpres, but you’ll be able to see from the downloaded pdf that in July we had 17 out of 31 days when the E.T was > 3.5mm and that included a period from the 4th to the 24th July, when there was no rainfall. In other words we had 2 1/2 – 3 weeks of elevated plant stress. I’ve actually graphed out July to illustrate this.
Of course the recommended irrigation requirement is based on 50% of E.T loss, but as mentioned last week, this will depend on any number of other factors, specifically rootzone type, shade levels, grass species / sward composition.
All the best for the coming week.