Oilseed rape faces an uncertain future as pressure from cabbage stem flea beetle extends across the country. Strong establishment helps the crop grow away from adult flea beetle attacks and resist larval damage in spring and there are a number of approaches to drilling.

Seeding from the back of a cultivator or subsoiler gained popularity in the early part of the 21st century for its low cost and high output. But some growers have moved on to using a cereal drill or even a precision planter to place the seed at set spacings, with the aim of getting stronger, more even establishment and specific plant numbers. Trials have also considered wide spacing of plants to encourage branching and boost yields.

Comparing methods, we catch up with two different farmers taking two different approaches to oilseed rape establishment.

Cost-effective establishment is helping to keep oilseed rape as a viable crop for Fenwick Bros, Grimsby, north east Lincolnshire.

Acreages have decreased in recent years, however, as Jonathan Fenwick explains: We have reintroduced sugar beet and moved to letting out land for potatoes to reduce our reliance on oilseed rape because of the issues facing the crop.

The business grew 130 hectares of OSR in the 2019/2020 season on its own land, plus contract work, using either a subsoiler-mounted seeder or the grain drill if the customer prefers that.

We believe simple is better and using a subsoiler means we can retain moisture at a time of year when it is in short supply. It gives the best establishment and it is cost-effective.

The He-Va seven-leg subsoiler is fitted with an Opico Variocast seeder and Nitrojet applicator which puts liquid fertiliser down the leg ahead of the seed.

This gets the taproot down by encouraging it to follow the nitrogen, explains Mr Fenwick.

A second Variocast is fitted to a He-Va Combi-Lift pre-cultivation tool to provide back-up.

The subsoiler is fitted with narrow points rather than wide sweeps to prevent large slabs being brought up on the heavier land, and we follow it with a heavy roll or press which gives improved germination, he says.

Mr Fenwick says it is not essential to use a subsoiler, any solid tine cultivator would provide the required loosening action.

Taproot

We are only going in to 25-28cm rather than providing a true subsoiling action a strong taproot at this depth will put out fibrous roots and give the crop a good chance. The narrow points also minimise soil disturbance which we believe helps combat flea beetle.

A 380hp John Deere 8335 RT tracklayer is used for all cultivations, which easily handles the four-metre subsoiler.

The Variocast and Nitrojet, which Mr Fenwick also experimented with mounting on the front linkage, stay fitted, but the second seeder comes off the Combi-Lift once all OSR is in as it is used for other jobs.

He reckons it takes a couple of hours to fit each season. The Combi-Lift replaced an older model last year while the subsoiler has been in the fleet for a number of years.

He-Va implements have been updated recently, but I cannot see us swapping the subsoiler as it is easier to keep beefing it up as needed, he says.

Seed rates are one to 12kg/ha, with row widths at 50cm.

We do not want too much seed in the row as branching is better with well-spaced plants and it makes no difference to its resistance to flea beetle. With hybrids at £200/bag we do not want to waste seed, he says.

Contract charges are the same whether the subsoiler or drill is used, at £62.43/ha plus fertiliser, while rolling adds £14.20/ha.

Results ahead of the 2020 harvest were varied, he says.

We have got one very good piece, and a field that was severely flooded has come back surprisingly well, except in the area which had standing water for a long time.

In another field, half is okay and the jury is out on the rest. We decided to stop work on 10% of the area, which has had no more fertiliser or sprays.

Mr Fenwick says he will cut his OSR area again this year, especially in light of falling oil prices.

Prices are not encouraging, particularly when you know you will be unable to harvest all the crop at its full potential.

On the Wills Estate, Edgcote, which straddles the North Oxfordshire and Northamptonshire borders, manager Hamish Gairdner has swapped to precision planting in an effort to help oilseed rape grow away from flea beetle.

Part of a four-year rotation on 670 hectares of combinable crops with two wheats and spring barley or beans, plus some grass, 150ha of OSR was established for this year.

For the 2018/2019 season, establishment was switched from a Vaderstad TopDown and mounted BioDrill to the Swedish manufacturers Tempo precision drill. Ground preparation is carried out with the TopDown, fitted with Grange low disturbance legs in place of every other leg at 52cm spacings, and a six-row Tempo R has been bought.

The Tempo is set at 50cm spacing working into the small amount of soil disturbed by the Grange leg, and we use RTK to ensure accurate guidance of the planter, says Mr Gairdner.

We always double rolled after the BioDrill to ensure seed to soil contact and retain moisture, and this has continued with the Tempo as I believe this is the most important cultivation pass you can make, he says.

But the Tempo must be set up correctly to avoid producing a ridge the roll cant consolidate.

He adds that if this can be achieved, the Tempo produces a level seedbed.

The star wheels at the front need to be adjusted to just clear any trash, rather than moving too much soil.

Residues

We bale wheat straw, so after this the pressure of the coulter is sufficient to cut through the trash; after barley where we chop the headlands, the wheels can be reset to move residues if necessary, he explains.

Setting the rear press wheels correctly is also key, he says.

We avoid using too much pressure which might create a large ridge the rolls can press down a 5-10mm ridge and give good seed to soil contact.

To test the system, Mr Gairdner initially engaged a contractor with a Tempo designed for maize, working at 75cm spacings, drilling twice to give 37.5cm row widths.

This was too close and we also tried drilling a section at 75cm, which showed no yield loss, but suffered from increased weed competition in the wider rows, hence the decision to choose the Tempo R with its 50cm spacing.

It is fitted with a 1,200-litre fertiliser hopper. In the first year, ammonium nitrate (AN) was placed down the spout, but for 2019/2020 it was swapped to the more commonly used DAP.

With reflection, the AN gave a better start, so we will return to that this year. Not only is it cheaper but it is more readily available to the crop.

Double rolling is an important part of the flea beetle strategy, then spraying is carried out at night to minimise impact on the estates 100,000-plus bees.

It is a strategy that seems to be working. Mr Gairdner says that corner to corner coverage is visibly better than with the BioDrill. In-row spacing is 5.5cm, with seed rates at 2.6kg/ha, and Mr Gairdner puts establishment at 95 per cent.

Seedlings emerge evenly over a three-day period, rather than at scattered timings, so there is less flea beetle pressure on individual plants, he says.

This years crops have been as variable as anywhere else, but Mr Gairdner is encouraged by last seasons results.