In this month’s Crop Walk and Talk Frontier agronomist Mike Barry shares his views on the latest agronomic issues affecting wheat, barley and oilseed rape crops in north Northumberland. Abby Kellett reports.
Despite high levels of winter rainfall, crops in the area have coped with the elements well, with rooting better than expected and disease levels fairly low.
However, the effects of excessive winter rainfall can be seen in some barley crops, with leaves beginning to yellow due to lack of soil nitrogen.
Echoing the views of our last walk and talk agronomist, Mr Barry reassured us plant populations are optimum for this time of year, and suggested there was reason to be optimistic going forward.
Wheat crops, like most others, have established well, with Mr Barry confirming an emergence rate of about 88 per cent from a 250 seeds per sq.m sowing rate, giving an established plant populations of 220 plants per sq.m.
He said: “We currently have about four tillers per plant, therefore the shoot count is currently between 900 and 1,000 shoots per sq.m, which is perfect for this stage in the season.”
Extensive rooting could be identified across all crops, with white roots suggesting recent new growth despite cold soil temperatures.
Mr Barry put this down to a mild autumn and therefore a large number of growing days prior to the winter period.
“New growth is encouraging since soil temperatures are only around four degrees at the moment.
“There is a school of thought that because we have had excess winter rainfall, plants won’t have put roots down to find moisture, because there would be plentiful supplies in the top layers,” he added, “but this does not seem to be the case.”
With wheat bulking up well above and below ground, attention turned to the disease status of the crop.
Septoria is the biggest concern, with quite a lot of older leaves affected. Although younger leaves were not displaying septoria lesions, Mr Barry warned these leaves could still be hosting the disease. Crops which had been drilled earlier were more likely to display septoria symptoms.
“Disease is a function of accumulated temperature, the leaves which have been around for longer have been exposed to the disease for longer and so are more likely to show symptoms,” he said.
He put the septoria disease threat as high. But while further south, yellow rust levels were high in many crops, temperatures further north were currently cold enough to prevent the disease taking hold.
He will be monitoring wheat crops for yellow rust in the next few weeks and will be hoping to plan a normal T0 fungicide application, aiming at the final leaf four growth stage, which he predicted will be at the end of March.
Other regions may require an alternative strategy. “Further south, the T0 application will be about two weeks ahead,” he said “But if I did have crops with yellow rust, I would go in possibly before the T0 application with a pre-T0 to control it.”
Although mild weather had been beneficial for crop rooting and establishment, it had provided an extended period for aphid activity. This posed a risk of barley yellow dwarf virus transmission, even for crops which were treated with a seed treatment.
“We treat crops with Redigo Deter, which stops the aphids feeding for six to eight weeks. But the mild November and December meant we had aphids coming in after that and there is still a risk of aphid infestation so close monitoring is required,” he said.
Commenting on the importance of monitoring soil trace elements levels at this time of year, he said the farm suffered from manganese deficiency and so he planned to incorporate a manganese foliar treatment into the fungicide programme.
“The plan is to apply a manganese foliar treatment before T0 or if possible at the T0 time.”
He would then hold off on nitrogen in order to optimise tiller numbers.
“Because this crop follows OSR, I am hoping mineral nitrogen levels are sufficient to keep the crop growing until mid-March. Because tiller number and plant populations are optimum, I am not keen to go on too early with too much nitrogen to encourage excess tillering.”
Winter barley has been drilled at 400 seeds per sq.m and establishment has been about 75 per cent, with plant populations currently at around 300 plants per sq.m.
The crop was at growth stage 22. “We have the main stem and two tillers. This in theory will give us a total of about 900 heads at harvest, which is perfect at this stage of the game.”
New crop growth was very clean, although crops had some areas of mildew on older leaves. However, Pearl had good mildew resistance and so other more susceptible varieties might be suffering more from mildew outbreaks.
“KWS Glacier, Cassia and Retriever have high susceptibility. Crops further south are also more likely to be suffering,” said Mr Barry.
Although mild weather was suppressing disease levels in the North, Mr Barry was still planning on applying a protective T0 fungicide in order to keep shoot numbers optimal. This will be applied alongside a growth regulator to encourage the development of secondary tillers and to reduce the risk of lodging.
Although all crops are likely to have had nutrients leached as a result of excessive rainfall, because barley nearly always follows a cereal, nitrogen levels are likely to be particularly low. This has resulted in areas of yellowing, particularly on the headland where soil is compacted. “In simple terms the crop is hungry,” said Mr Barry
High peat levels on the farm had proved problematic in terms of trace element availability and herbicide effectiveness.
“There are high peat levels which tend to lock up trace elements such as manganese, so there has been some localised plant loss, despite an application of manganese in autumn.”
In response to sterile brome infestations, a pre-emergence application of Vygon (flufenacet) and Liberator (flufenacet + DFF) were applied, followed six week's later with a half-rate of Liberator alone.
“Because the field has peaty soil, some of the herbicide has been absorbed onto the soil particles, which has allowed some weeds to emerge, including OSR volunteers which will need to be controlled at T1 time.”
Good autumn growing conditions have meant oilseed rape has established particularly well with about 75 to 80 per cent establishment. This has resulted in a total plant count of around 30 to 35 plants per sq.m from a seed rate of 45 seeds per sq.m.
The crop was at a critical growth stage in terms of thinking about applying nitrogen.
“We have nine or more leaves and are just beginning to enter into stem extension, so this crop will be looking for its first dose of nitrogen as soon we can travel.”
The tap root was surprisingly well developed in this crop, with most plants having a tap root reaching about 30cm, which is encouraging for this time of year.
Although there are reports of light leaf spot further south, in particular where crop canopies are dense, further north crops are suffering from very little disease.
See also: Keeping ahead of light leaf spot
Some older leaves displayed areas of phoma, but new growth was generally clean following an application of Prosaro (tebuconazole + prothioconazole) in November, which aimed at protecting against both of these fungal diseases.
An application of Naspar TDI (metazachlor + quinmerac) post-emergence had been followed by an application of Kerb Flo 500 (propyzamide) and had done a satisfactory job at controlling both grass- and broad-leaved weeds.
Since crops are covering the ground well, Mr Barry did not anticipate high weed pressures going forward.