Align oilseed rape drilling to soil moisture, growers urged

Align oilseed rape drilling to soil moisture, growers urged4 August 2022

Winter oilseed (WOSR) rape growers facing continued dry soils should not rush into drilling the crop too early, says ProCam technical development manager, Rob Adamson.

According to Mr Adamson, there has been a shift to drilling WOSR earlier in recent years, primarily with the aim of getting crops established ahead of cabbage stem flea beetle attacks. Moreover, this tactic could be tempting this year, he says, because fields have been cleared by the early cereal harvest.

But where soil moisture deficit is significant following the parched July, this could be disastrous for WOSR establishment, he warns.

“Moisture is fundamental to crop germination,” says Mr Adamson, “and particularly so with oilseed rape seeds which need to take up 40% of their own weight in moisture before germination can even begin. There is then a second moisture requirement to allow the seed to produce an embryonic root.

“From a practical perspective, this means crops need to go into moist seedbeds and have more moisture on the way. Drilling before this is unlikely to be successful.”

Dry conditions during the first half of August do not mean the crop should automatically be abandoned, says Mr Adamson. However where drilling is delayed into the second half of August to achieve sufficient soil moisture, he says this will increase the need for good seedling vigour, and in these situations hybrid varieties can prove their worth.

“Hybrid vigour can help to mitigate the delayed start. The improved growth rate of hybrids means they can still reach a size where they stand a chance against cabbage stem flea beetles when the migration begins.

“As well as hybrid vigour, using biostimulants to encourage rapid growth of a crop drilled later into sufficient moisture can also aid successful establishment. With both seed and foliar-applied biostimulants available, these treatments are a worthwhile investment: while insecticides face resistance, it is possible to reduce the effect of adult cabbage stem flea beetle by ensuring the crop’s growth rate exceeds the feeding rate of the adult pest.

“Maximising this growth rate is critical whether growing conventional or hybrid varieties. But the vigour of hybrid varieties can potentially be used as an extra method to maximise growth when time is of the essence.”

With good OSR commodity prices and a successful harvest this summer, Mr Adamson says the appetite to grow WOSR among farmers is the highest it’s been for several years. As well as income from the WOSR crop itself, he says the crop’s benefits for maximising first wheats in the rotation can also not be ignored, but rushing to drill WOSR before there is adequate moisture could easily result in disappointment.