Hungry crops show signs of nitrogen deficiency

This week’s arctic blast of wintery weather has halted any thoughts of fieldwork happening in the coming days, as our Crop Watch agronomists focus on hungry-looking crops.

Many crops need their first fertiliser dressing, as they start to show symptoms of nutrient deficiency, with a range of yellowing and purpling being seen.

Potato growers will be hoping that the cold spell kills off troublesome aphids, which have benefited from milder winters, as seen in recent years.

Marcus-Mann

Marcus Mann

East: Marcus Mann

Frontier (Essex)

Winter certainly has not finished, as we endure what could be the coldest February week for the past five years. One or two milder days at the beginning of February saw some crops start to move a little, but there will be little further activity until we start to see an appreciable rise in soil temperatures.

Oilseed rape has started to show some growth since daylight hours have begun to increase and will require its nitrogen and sulphur as it starts to grow away.

Fortunately, the colder winter has prevented the canopies becoming too large, which will enable larger nitrogen doses earlier on in the season.

See also: How to stop blackgrass adapting to a spring cropping strategy

However, be mindful of light leaf spot, as even if its symptoms have yet to show, it is being reported on incubated leaves.

Propyzamide has shown good efficacy this year, with a colder, damper winter aiding blackgrass control.

The aminopyralid in Astrokerb (aminopyralid + propyzamide) has also ensured there will be no emergency applications of Galera (clopyralid + picloram) later on for thistle, mayweed and cleaver control. Currently, temperatures would be too cold for effective clopyralid control.

Pleasingly, the same can be said for residual herbicides in cereals this year. During the much-drier-than-normal autumn there was speculation about the effectiveness of the residual programme. Where robust treatments were applied, it gave enough persistency to last until suitable conditions enhanced the control.

Yellow rust has begun to show in susceptible varieties. The colder weather will help suppress this, but be mindful that when it becomes milder, it will spread very quickly once the crop moves through its growth stages.

Cereals will certainly need feeding, with both nitrogen and manganese deficiency becoming apparent. Last year proved that early timings of nitrogen were critical in crops that didn’t have the residual N reserve from a previous break crop.

Kevin Knight

Kevin Knight

South: Kevin Knight

Zantra (Kent)

Winter cereals have fared well thus far, though some wheat crops are purpling due to phosphate hunger, and wetter areas are yellowing as manganese reserves run low (possibly indicating compaction needing attention after harvest).

Winter barley is looking jaundiced in places, but that will go once it picks up some nitrogen. I’m keeping an eye on mildew in oats and some wheat varieties, especially Basset, Cordiale and Zyatt. Siskin is carrying plenty of brown rust.

Early growth regulators and nitrogen will need to be applied to second and late-drilled first wheats that are a bit low on plant count in places to encourage tillering and reduce apical dominance in an effort to achieve an acceptable yield.

Winter barley and oats will need growth regulation once growth starts, especially given the challenge of last year.

Forward OSR

Oilseed rape is looking good – too good in places, where earlier-drilled crops are very lush. The autumn fungicide did a grand job and disease levels are low. Phoma is beginning to show again, but there is no sign of light leaf spot where suspect leaves have been incubated.

The pigeons hadn’t taken their toll at the time of writing, though the flocks are beginning to build and they are dropping into rape in this cold spell.

Some have started top-dressing OSR and grass, as always happens when we have a warm “blip” at the back end of winter, before this week’s Baltic blast to remind us that it is still winter.

Crops won’t use the N until they start growing, and in OSR, that is usually once soil temperatures are consistently above 4C. Judging when that will be is tricky – as you really want the fertiliser on the crop 10-14 days before it is needed.

Fertiliser application driven by data, conditions and experience generally brings better results than deciding by calendar date.

Patrick Stephenson

North: Patrick Stephenson

AICC (Yorkshire)

February is the month when consultants emerge from their winter hibernation, which consists of meeting after meeting and conference after conference. If we add to this the endless number of nutrient and fertiliser management plans, we are all like “caged mad March Hares” itching to get crop walking

Crops have come through the winter well and look good, with rich green colours not being uncommon in many winter wheat crops.

The early-drilled crops of oilseed rape are now starting to stem extend and with the winter barley starting to show its washed-out pallet of yellow, everyone’s thoughts are turning to top-dressing nitrogen.

It is critical that both OSR and winter barley get the major part of their nitrogen requirement before early April. As I point out to growers, this is not a competition to produce the deepest tramlines, but a signal to apply nitrogen when conditions allow.

Blackgrass survivors

Weed control on the whole has been excellent and although some blackgrass has survived, overall I am very pleased. A winter that has at long last contained some frosts has meant the propyzamide applications have achieved good levels of blackgrass control.

Broad-leaved weeds in cereal crops are noticeable by their absence and groundsel and fumitory appear to be at lower levels than usual. I use this early crop walking to map out weed hotspots and monitor for disease development.

Wild oat germination has started early this year, which really helps to enable good control from early-season broad-spectrum sulphonylurea products. 

Early-drilled wheat in the North have produced large canopies that are ideal for septoria development. Although we have many crops of Siskin and Graham, with good inherent septoria resistance it is still easy to find the disease.

I have now seen yellow rust on the late-drilled wheat and hope the cold weather will slow the development of this early infection.

It is too early to call what this season will bring, but with wheat prices of £150/t and autumn crops looking well, I start the season in an optimistic mood

Giles-Simpson

Giles Simpson

West: Giles Simpson

Pearce Seeds (Somerset)

The weather has gone from wet to very cold and the ground is drying out on top while it is still very wet underneath. The constant rain over the winter has meant no fieldwork has been done.

Some late-drilled wheat will have to be redrilled, as the crop has rotted. It went into wet ground after maize and has been sitting in water ever since. Some will be drilled with spring barley, but some areas will be sown with wheat or oats and then used for wholecrop silage. 

It does show the need for early maize harvests and with people currently ordering maize seed, I strongly suggest going for the earliest-maturing variety you can and choosing fields carefully.

In Dorset we have a Dorset Maize Charter Scheme that involves an independent consultant going on farm and assessing fields individually to give a maturity class of maize that should be sown in each field. Many fields are now growing much earlier varieties than they would have done historically.

Manganese deficiency

The wheat that went into the ground in good time last autumn generally looks well, although manganese deficiency is now showing in many crops. Septoria is present and yellow rust is noticeable in susceptible varieties. Second wheats will need an application of nitrogen as soon as possible.

Barley is generally well tillered – even hybrids drilled late in October look well. The cold weather has knocked down any mildew present. They will need an application of nitrogen as soon as ground conditions allow.

The autumn herbicides have worked extremely well and there are few weeds present, which is good. There were many fields that didn’t receive any autumn herbicide because of ground conditions and there is plenty of annual meadowgrass.