Getting the best from oilseed rape - Farmers Weekly

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Getting the best from oilseed rape

Oilseed rape growers don’t always need to sow all the seed they order and should pay more attention to drilling by seed number and recognising increasing phoma challenges.

As harvest results filter in those are key messages from Masstock’s Best of British Oilseeds initiative.

“Overall, winter oilseed rape seems to have had a good but not record-breaking year,” says the firm’s David Neale.

“But trials and grower feedback shows that there is a lot more variability than usual.

We are finding that as well as seed-bed quality and seed rate the other big factor has been phoma, especially where rotations are getting tighter.”

Barrel and ES Betty, otherwise good varieties with weak phoma resistance, have performed relatively poorly.

“It was no surprise to see Barrel second from the bottom of the list at the HGCA’s Oxon site.”

Last season’s growing conditions favoured low biomass conventional varieties such as Castille, non-recommended Caracas and phoma-resistant ES Astrid, says Mr Neale.

“We had a lot of good autumn growth, plenty of residual nitrogen and a wet spring followed by a short flowering period, and a lot of crops accomplished our 5t/ha target.”

Hybrid Excalibur performed consistently well irrespective of sowing date, with the added advantage of being a week earlier to harvest.

That is an important issue in trials data, as the variety will lose yield if combined too late, he points out.

Another, Excel, with top phoma resistance rated at 8 also did well in BoBO trials.

“Although like other bigger, taller hybrids they seemed to suffer under the drought pressure in June.”

The notion that they are deeper rooting and so could withstand dry weather better is misplaced, he believes.

“It is more appropriate to position them for more difficult sites and later drilling, as their speed of development and recovery from pigeon damage is much better than the conventionals’.

Where farmers acted on our advice and reduced seed rates to sensible levels, so that they achieved around 60 plants/sq m in the spring for conventional varieties and rather less for hybrids, there have been quite a lot of 2t to 42cwt/acre crops.

“Where they got a good branching structure instead of a load of thin, dense upright stems their crops really shone through.”

Getting the best from oilseed rape

This year we’ve been tracking the progress of farm advisory group Masstock’s trials growing rape under three different cultivation regimes.

Our latest update includes root weights and pod counts.

The first plot received a fairly conventional but intensive cultivation regime.

It had two passes with a set of heavy Simba discs and the seed was drilled with a Kuhn power-harrow combination.

For the second technique, an Opico HE-VA Disc-Roller disc/press combination with Variocast seeder-unit was employed.

On the third plot, a Variocast seeder-unit piggy-backing on the sub-soiler was used to drop seed behind each soil-loosening leg.
The last of these methods clearly scores best on cost and, at the end of March, the crop established under this subsoiler regime was the one that had reached the highest Green Leaf Area Index (GAI).

By the end of May it was clear that seedlings able to establish themselves directly in the subsoiler legs’ wake were making the most of their rooting potential.

The average root weight where seed was spread behind the subsoiler was more than 75% greater than those established using conventional cultivation techniques.

A week or so into June, most viable seed pods are set and again the subsoiler-seeded crop leads the field with the most pods per plant – 42% more than the crop established with the disc/press combination.

The main reason is that, because of its greater root mass, the subsoiler crop has been able to access more nutrients and water than the others.

Also, because the plants are growing in 50cm (20in) rows, they have more room to branch out to fill the gaps and can intercept more light and form more viable pods.

Getting the best from oilseed rape

Farm advisory group Masstock uses a number of “Smart Farms” dotted around the country to compare various crop husbandry practices.

This year oilseed rape specialist Philip Marr has set up a field-scale trial to assess the merits of three OSR establishment methods at the company’s Brotherton Farm near Pontefract, Yorks.

One of Philip’s key tips is to make a sub-soiler pass before planting OSR.

He argues that most farms will be performing the operation at some point in the rotation and doing so ahead of rape maximises the crop’s rooting potential.

OSR can really exploit an open seed-bed and its root structure is such that the soil is left loose for the following crop.

Top Tips for OSR establishment
– Avoid using one variety across farm, choose types to suit seasonal conditions and to spread harvest time pressures.

– Minimise seed rates. Aim for about 60 seeds per sq m which should equate to 40 plants per sq m in spring. E.g. Lioness @ 2.5kg/ha and Caracas @ 3.7kg/ha.

– Be aware of variety thousand seed weights and adjust seed rates accordingly. E.g. 1kg Lioness = 232,000 seeds; 1kg Caracas = 158,000seeds.

– Score seedbed conditions on the day. Increase or reduce seed rates accordingly.

– Attribute costs per tonne rather than per acre/hectare. That way expenditure can be instantly compared with crop returns.

– Consolidation is key – rolling won’t do any harm if it rains but could be the difference between crop failure and success in a dry year.

Consequently each of the Masstock plots was subsoiled.

In addition the whole area was rolled to ensure moisture conservation.

The cost of these passes is included in the final figure.

The first plot received a fairly conventional but intensive cultivation regime.

It had two passes with a set of heavy Simba discs and the seed was drilled with a Kuhn power-harrow combination.

For the second technique an Opico HE-VA Disc-Roller disc/press combination with Variocast seeder-unit was employed.

On the third plot a Variocast seeder-unit piggy-backing on the sub-soiler was used to drop seed in a band behind each soil-loosening leg.

OSR Establishment technique
. Establishment method Subsoil, disc x 2, power-harrow/drill, roll Subsoil, disc/press/seed, roll Subsoil/seed, roll
Cost £130/ha £75/ha £48.25/ha
Advantages – stubble incorporation
– consistent establishment
– consistent 12.5cm (5in) row spacing
– high speed
– seed-to-soil contact
– minimal disturbance in stony conditions
– low cost
– moisture conservation
– minimal weed seed disturbance
-utilises existing sub
-soiler pass
Disadvantages – high cost- time consuming- weed seed disturbance – unnecessary pass if sub-soiling- variation in seed depth- weed seed disturbance – slower output- untidy finish
GAI* on ?10th Mar? 1.4 1.5 2
NB – Costings from Nix Farm Management Pocketbook 2005. *GAI measured by collecting green leaves from 1sq m of crop. This is then weighed and multiplied by a factor of 0.8. Generally if GAI = 1, total leaf area = 1sq m. At early growth stages GAI closely correlates with root development.

Clearly the first technique proved most expensive and the final one cheapest. But that is not all that needs to be considered.

Germination rates, light interception capabilities and of course the final yield all need to be compared.

We’ll be following the trial through the growing season.

First up, we kick off with measurements of the canopy area – Green leaf Area Index (GAI) – as temperatures begin to rise and plants prepare for the spring growth spurt.

GAI scores are highest in the subsoil only plots because seed was dropped directly behind the subsoiler leg, allowing the tap root to quickly establish itself straight down into the loosened slot.

This means that the plants are able to gain access to nutrients (mainly nitrogen) more effectively.

In the other establishment plots, (GAI 1.4 and 1.5) the roots are smaller and found nutrition more difficult to obtain.

We’ll return to the trials for an update as plants reach stem extension – late April/early May.

Did you know?
  • 60% of seed is produced in the lower third of the canopy. Therefore light interception to the lowest pods needs to be maximised. Well spaced, branched plants will achieve this best.
  • Minimising seed rates at the Brotherton Smart Farm has brought average OSR yields up to 5.8t/ha. Yields of up to 7.2t/ha (2.9t/acre) were recorded last year.
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