Advice on growing peas to replace failed OSR crops

Combinable pea drilling is well under way across the UK, and farmers will need to be on top of their agronomy if crops are to perform, in what could prove to be a challenging season for the pulse. 

Some farmers have replaced a proportion of their failed oilseed rape with the spring crop, with the hope of salvaging some income, as good-perfoming crops can reward growers with good profits to be made. 

However, they are sensitive to compaction, and after such a wet winter, there have been challenges with creating good seed-beds, especially where peas are replacing failed oilseed rape, acknowledges independent pea consultant Keith Costello.

See also: How to hit quality specs with marrowfat peas

Furthermore, the loss of thiram as a seed treatment means that seedling losses from damping-off caused by pythium species are a greater threat this spring – even though the broader-spectrum treatment Wakil (cymoxanil + fludioxonil + metalaxyl) remains approved for sowings from 1 April.

Therefore, crops will need all the help that growers can given them to succeed.

To help farmers, here are six key areas to consider: 

Combining peas

  • March/April – drilling, rolling, pre-emergence herbicides
  • April/May – plant counts, post-emergence herbicides, micronutrients
  • May/June/July – micronutrients, insecticide, fungicides
  • July/August – desiccation, harvesting, storage

1. Rolling

Crops that were drilled to the right depth and rolled pre-emergence have been less at the mercy of birds and able to access seed-bed moisture.

While most crops will have been rolled at this stage, where soil conditions were unsuitable, it is still possible to roll peas post-emergence with minimal damage, advises Mr Costello.

“Ideally, roll when the peas are 3-7cm high (growth stage 12-13) on a warm afternoon when they are slightly rubbery, using the lightest equipment capable of levelling the soil at speed.”

He adds that growers should try to “glide” across the field, as travelling too slowly can cause compaction, while going too fast causes the rolls to bounce.

2. Weed control

Pre-emergence herbicides, which are dependent on soil moisture, have a crucial role as post-emergence products are very limited in number and not as effective.

For this reason, Mr Costello believes it’s better to get a pre-emergence herbicide on, even in a dry season, so that the first flush of weeds is suppressed and remaining plants are sensitised.

3. Plant population

Target plant populations are 65 plants/sq m for marrowfats and 75-80 plants/sq m for blues.

Patchy establishment can be caused by not drilling deeply enough, but disease and lack of moisture are also threats.

Most popular varieties

  • Large Blues – Karioka, Mankato, Prophet, Daytona, Kingfisher
  • Whites – Karpate, Kareni
  • Marrowfats – Kabuki, Sakura

“Either way, do a plant count and know what your field losses are.

“Any higher than expected field losses could well be due to poor drainage this year.”

Micronutrient deficiencies were picked up in leaf tissue samples submitted for the pea YEN competition last year, but there’s insufficient knowledge on them to make firm recommendations, he says.

4. Micronutrients

“We do know that manganese is very important for peas, and magnesium could be too. Crops being grown on soils with a pH of 7 and above must have manganese applied at flowering.”

Applying manganese with an insecticide for pea and bean weevil is fine, but it shouldn’t be applied with herbicides, he warns.

“If it is, the plant will open up, making it susceptible to herbicide damage.

“Ensure that the plant leaves are fully waxed before going back with the herbicide.”

Another reason for applying manganese is to prevent the quality issue marsh spot, which can lead to rejections.

It is less clear whether the application of other micronutrients such as boron and molybdenum is necessary, but is unlikely to do any harm.

“Apparent deficiencies are common, but we don’t know whether they matter or not.

“There’s still quite a bit to learn on micronutrients.”

5. Pests

Pea and bean weevil only needs controlling where very high levels of notching damage are seen at the end of April.

“Follow PGRO advice on trapping to assess whether threshold numbers have been reached – the thresholds are surprisingly high, but the pest may be a bit ahead this year after such a mild winter.”

Pea YEN findings – critical success factors

  • Weather
  • Crop establishment
  • Roots and root structure
  • Aphid vectors and viruses
  • Micronutrients
  • Grower knowledge

Virus-transmitting aphids tend to come in earlier than most growers expect them to, says Mr Costello.

“These viruses can be very damaging to yields. The aphids responsible are found at the base of plants and their numbers can be assessed by swiping the plants when they are 4-5in tall, then looking for aphids on the soil.”

He picks out the pea enation mosaic virus (PEMV) as it is now being seen every year and is spread by the pea aphid.

Biscaya (thiacloprid) is still approved for 2020 and can be used for early-season aphid control.

Aphox (pirimicarb) can only be used once, so growers must plan their control timing carefully at flowering time.

6. Disease control

In terms of fungicide use, first pod or maximum flower (growth stage 65) is a key timing to minimise losses from botrytis.

“That should then be followed up 14 days later, if the weather means a second application is necessary.”

Take note of any changes to harvest intervals before spraying, advises Mr Costello.

His final point is that timeliness at harvest is essential.

Once the crop has reached 16-18% moisture, it should take priority on a hot, sunny afternoon or it will become too dry and can be rapidly bleached by the sun.

“Peas are a specialist crop and they have to be treated as such.”

Further information

  • PGRO – for latest crop information, R&D work, variety advice, technical updates
  • AHDB – for Aphid News – a regional, weekly updates on aphid species and numbers

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