Crop Watch: Cereals and agronomists stressed by drought

Dry conditions are having an impact on crops and Iain Richards says those on gravel appear stressed, although spring barleys are still looking good.

The dry has seen Andy Goulding opt for a foliar feed for oilseed rape because conditions are not so favourable for the utilisation of N in the soil.

Stephen Harrison adds that moisture problems for wheat will really kick in once the so called “grand growth” period in May begins. 

See also: Catch up with previous Crop Watch pieces 

Finally, Sean Sparling urges growers to avoid cutting back on fungicides at T1 believing the dry conditions have reduced the risk, because the threat remains.

Iain Richards

Iain Richards

South: Iain Richards

Agrii (Oxfordshire)

Having set up our wheats with good early plant growth regulation, micro-nutrition and disease control, we’re looking forward with our T1s rather than having to chase problems. An early April T0 and hardly a drop of rain since has held septoria back nicely.

Crops on the gravel are now starting to look decidedly stressed, though. But even on the chalk we’re seeing the value of the extra manganese and zinc we included at T0 in greener, stronger and healthier crop growth.

We’re already finding clear magnesium and boron imbalances in our tissue testing. So we’re including these trace elements at T1 where necessary, rather than leaving them until T2. Dry weather invariably increases crop stress, and we know from our research how valuable micro-nutrition can be in relieving this and prolonging green leaf area.

With septoria continuing to be very visible in the base of most crops and the curative armoury more stretched than ever, we’re using an SDHI at T1 as well as T2 in most cases this season, supported with a different azole to T0 plus a strobilurin on yellow rust-susceptible varieties.

We’re doing this because we can’t afford to assume the weather will stay dry. Conditions are set fair for T1 spraying, so we’re taking the opportunity to give what protection we can to leaf 2 as well as leaf 3 and avoid any T1.5 need should conditions change. At the same time, we want to minimise any risk from weather-enforced T2 delays.

Despite the dryness, our spring barleys are looking good. Many didn’t go in until April, but pre-Christmas primary cultivations, minimal spring soil working and patience for the right drilling conditions have again been rewarded.

The crops have found some decent moisture to get to three strong leaves and are now receiving extra manganese and magnesium with their PGRs, together with the rest of their nitrogen.

Andy Goulding

Andy Goulding

North: Andy Goulding

CAS/Hutchinsons (Cheshire)

Growth regulation in winter wheat with Medax Max (prohexadione + trinexapac) + chlormequat combined has proven to be an effective strategy with three actives.

The prohexadione has been working well in cool conditions and tillers had evened up a bit with the T0 spray; second doses are now nearing completion along with T1.

This has allowed as many leaf 3s to be targeted on the secondary tillers because it has the main stems.

It is somewhat surprising that Evolution has been found to be harbouring some fierce foci of yellow rust just before T0, which is currently with NIAB’s virus surveillance team. I’m exercising caution in all cases, and with these events it highlights the importance of thorough crop walking.

Winter oats will be getting some robust plant growth regulators this time in response to larger N doses, in order to push yields higher than of late. They are currently looking clean with only mildew and abiotic spotting present. Actives in the main are strobilurins plus mildewicides.

Early potato crops that are unfleeced have started to come through, and pre-emergence herbicides with higher solubility are my choice at present – these include Shotput (metribuzin) and Inigo (metobromuron).

Trials involving nitrogen being applied into the ridge as a liquid along with a nitrification inhibitor are underway. This should, hopefully, make for good results, given the length of time between application and uptake on these leachable soils.

Oilseed rape is receiving some supplementary N as a foliar application. In current conditions, it is prudent to go directly into the leaf while conditions are not so favourable for utilisation of N in the soil.

This method of nutrition can also be well-utilised in potatoes and maize (when uptake can often be later than when traditionally applied).

Sean Sparling

Sean Sparling

East: Sean Sparling

AICC/SAS Agronomy (Lincolnshire)

There has been plenty of sunshine and dry weather up here in Lincolnshire, but very little in the way of warm temperatures. As I write this piece, it is 9.2C in the sun and we have had a mere 6.2mm of rain in April.

The dry conditions mean spring crops are struggling to get going: several fields of sugar beet, which have now been drilled for over three weeks, have large areas within them where the seeds are yet to start; and spring cereals, which initially emerged well having been drilled into moisture, are flagging by the day.

This has not been helped by two concurrent -3C frosts in the last few days – nothing like kicking a man when he’s down!

Weed control in sugar beet is proving interesting, with residual pre-emergence herbicides doing little of note in the dry conditions. But the weeds are struggling just as much as the crops, and when herbicides are applied the effect on them is almost instant and very impressive.

I have been holding my growers off spraying newly emerged fields of sugar beet in the current frosty spell, because the combination of herbicides and adjuvants along with frost and stress is not a happy one.

In winter barley disease levels remain moderately low, with abiotic spotting, net blotch and mildew showing far more widely than rhynchosporium. Flag leaf fungicides are imminent over the next 10 to 14 days on hybrid barleys in particular, but not exclusively.

Things could easily turn very wet as they have done many times before, so, in an area where rhynchosporium is always a potentially major problem, prothioconazole will be the weapon of choice at flag leaf.

Yellow rust is beginning to resurface in winter wheat – not just in the usual suspects but also in relatively clean varieties such as Lili.

Septoria levels remain worryingly high in the base of almost every field you look at, but T0 fungicides based around strobilurin + chlorothalonil appear to have done a superior job to tebuconazole + chlorothalonil at both keeping the yellow rust and septoria in check as well as keeping the canopy green.

Growers should not make the mistake of cutting back just because it is dry and they perceive the septoria threat to have diminished. The threat remains and if you let it get ahead of you at T1 you’re going to be behind it for the rest of the season.

Stephen Harrison

Stephen Harrison

West: Stephen Harrison

AICC/Southwest Agronomy (Avon)

Lack of rain is the constant conversation point in the last month. Spring crop establishment is the predominant worry, although it must be said that where good quality seed-beds have been prepared decent plant stands have emerged. 

In no till situations, the paramount factor influencing the quality of establishment is the time of destruction of any cover crop or regrowth from the previous crop. Where old vegetation was taken out while the soil was at or near field capacity adequate moisture was retained for the new seeds. 

I repeat the mantra “no glyphosate means no cover crops and no zero till”. Please carry on lobbying and if you are canvassed during the election run-up impress the important issues of glyphosate and neonicotinoids upon whoever is knocking on your door.

Rust is once again causing headaches and the yellow peril is flaring up in all sorts of varieties. Azoles or strobilurins have been included in all T0s.

Where timings are spot on it is not an issue, but in varieties such as Reflection, where the disease cycles so quickly, extra treatments have been required – especially as the cold, dry spell after earlier milder weather has meant intervals between T0 and T1 have been protracted. 

Wheat is not currently unduly drought stressed, but needs moisture for nitrogen uptake. Moisture problems for wheat will really kick in once the so-called “grand growth” period in May begins, when crops are looking for 3mm per day of soil moisture or rainfall.

Oilseed rape is well into pod set and all crops have been treated for sclerotinia, otherwise known as “a riddle wrapped up in a mystery inside an enigma”.  The disease seems to be no respecter of its own biology. 

I well remember 2007 when the conditions seemed impossible for the disease, but we had a very severe outbreak in spray misses. If flowering continues beyond three weeks after the first treatment, a second spray may well be required.

I mentioned 2007 – in that year a very dry April turned into a wet May. Our climate seems to be turning into spells of extremes. Oh, for the happy medium!