Establishment: why it pays to be POSH resistant

Heavy rain late in the season is highlighting the need to consider pod shatter resistance when selecting oilseed rape varieties.

Pod shatter (POSH) is a natural process for seed dispersion in oilseed rape. But it can result in significant on farm seed losses due to extreme weather – including heavy wind, rain, hailstones, or the combine passing through the crop.

Built-in POSH resistance is an important attribute when seeking to protect rape yields through to harvest – and keep the crop profitable, says Kurtis Scarboro, arable development officer at plant breeder Limagrain.

Yield potential

 “Almost all the costs of growing the crop have been spent by this stage so it makes sense to protect yield potential right through to the end of the growing season,” explains Mr Scarboro.

“POSH resistance also helps to provide some flexibility in the timing of the harvest. It also cuts down the number of volunteers in the following crop, easing the burden of weed control, says Mr Scarboro.

“The most effective option for preventing pod shatter is a genetic trait, so it can’t be influenced throughout the season – making varietal choice very important.”

POSH resistance is measured by the force required to break open a ripe oilseed rape pod. Results from lab-based techniques used by Limagrain show that some varieties are more resistant than others, says Mr Scarboro.

Wet and windy

“All Limagrain hybrids contain the trait and we constantly monitor the efficacy of our pod shatter resistance against other commercial varieties so we can be confident in our claims that the variety really is pod shatter resistant.”

The benefits of robust pod shatter resistance were clearly seen in an exceptionally wet and windy 2023; July saw one of the wettest and windiest months on record for the last 188 years, followed by the windiest day for the last 55 years.

“While some oilseed rape crops were devastated, others appeared relatively unscathed,” says Mr Scarboro. “This undoubtedly comes down to robust pod shatter resistance.”

Joe Bayford of Keyston Farms won’t grow a variety without POSH resistance. Farming more than 600ha near Huntingdon, he believes it is critical to protect rape yields all the way to the trailer.

Despite reducing his rape area, Mr Bayford says the crop remains important. “We are only growing about half of what we used to, but we still find oilseed rape a valuable crop in the rotation behind either spring or winter barley.

Making the switch

Keyston Farms switched to hybrid rape from conventional varieties about six years ago. Mr Bayford says yields have increased by up to 0.5t/ha yield since doing so – an achievement he attributes to genetic traits such as POSH resistance.

As an extra insurance, Mr Bayford applies pod stick. “If we can get around 3t/ha for the crop then we are still making money – anything less than that and it starts to drag down the gross margin.”

Mr Bayford grew Aurelia and Attica following advice from Jonathan Payne of Nickersons. This year he is trying LG Armada, which again is another step on in genetics and yield improvement.

“We noticed with LG hybrids when we rub the pods out to test for moisture before harvesting, they are much more stubborn to pull apart. Even with a hailstorm in 2021, the seed did not shed – whereas some local crops did.”

Establishing the crop has become a whole different ball game to beat cabbage stem flea beetle. The rape always follows a spring or winter barley with the aim to get drilled by the first week of August, conditions permitting.

 The aim is to have a well-established crop in the autumn, so by the spring it is big enough that emerging flea beetles are feeding on the stems and not on the growing points of the plant.

Back in action

“Last year we managed to drill most of the crop in the first week of August – until rain stopped play. A week later we were back in action, but our later drilled crop hasn’t coped as well.”

To further improve establishment, Mr Bayford adapted his Horsch Sprinter drill by taking out every second tine, working on 12 rather than 24 tines. “We are effectively working on 50cm rows, doubling the seed rate per row.

Seed comes primed with a phosphite and phosphate dressing as well as being polymer coated and dressed with Integral-Pro, all of which gives the seed an extra kick for a better start.

“Any gains at this stage can mean the difference between a crop and not a crop. We also put 150kg of Di-ammonium Phosphate down the drill, significantly improving the seed to fertiliser contact.”