Late OSR drilling works a treat in Aberdeenshire

Leading Aberdeenshire grower, Jim Reid finds late-drilled oilseed rape fits well into his seed potato and spring barley-based rotation, providing the canopy is set-up well enough to soak-up the mid-summer sun.

Climbing up away from St Cyrus near Montrose on the east coast of Scotland, the sun struggles to fight through the sea haar. Eventually it clears to a distant haze to reveal a high potential crop of DK Exsteel on the other side of Kirktonhill.

Coming into stem extension, there’s a nice even plant stand, but the crop is none too thick. This doesn’t worry Mr Reid’s and his Agrii agronomist Iain Anderson, though. “We drilled it on September 11 – deliberately late for this part of Scotland – and we’re not worried about going as late as 15 September. As long as it has a good tap root going into the winter, we know the top growth will compensate in the spring as the days get longer, stresses Mr Anderson.”

He carefully digs up a plant, and sure enough there’s a long, straight tap root extending a good 25-30cm into the medium loam soil. “Our whole focus here is on building a canopy to make the most of the long days we get in mid-summer.” Jim Reid farms 270ha of arable ground at Milton of Mathers with his brother Ron, 60ha of which are down to the seed potatoes that form the major part of the family’s business. These are grown one year in seven with three or four spring barley crops, a single OSR and one or two winter wheats between them.

“This is one of the best areas in the country for combinable crops, and we grow prize-winning malting barleys,” claims Mr Reid. “As well as the long daylength in mid-summer, the sea haar we get takes the edge off the summer heat. That gives us a good extended growing season.

“Last year, our OSR averaged 4.27t/ha with a good oil content. What’s more, coming in at 9% moisture it didn’t touch the drier and went straight onto the boat at Montrose docks.”

DK Exsteel was the best performing of last year’s varieties, grown alongside SY Harnas and Nikita. The Nikita has been dropped from this year’s 47ha of OSR because, while looking great, it failed to perform.

“The DK hybrid seems to be perfectly suited to our climate,” Mr Reid says. “It has the good vigour and speed of development we need with late drilling. Its pod-shatter resistance is also really valuable. We get some high winds off the sea, and if one of those comes through just before harvest, it can do a lot of damage.

“It’s also slightly later to grow away and mature than the other varieties we’re growing, although flowering at around the same time. You don’t want a variety that flowers too early here because you don’t get the pollinators until later into the spring. What is does really well is branch out to fill the space, flowering profusely to give us plenty of pods to soak-up the mid-summer sun.”

Mr Reid’s recipe for success with OSR starts with breaking-up the ground after spring barley with a 3m Sumo DTX 300, preparing it well enough but leaving sufficient stubble standing to deter the pigeons.

The crop is then sown with a 3m Amazone one-pass combination drill. “We’ve tried drilling in wide rows but all that does is provide a landing strip for pigeons,” he  points out. “Broadcasting doesn’t work either, as the correct and  even seed depth is critical; as is rolling for the best seed-to-soil contact.

“We use a seed rate of around 50/m² to target a final plant stand of about 25-30/m², adds Mr Anderson. “It’s that first month that’s crucial for OSR in Scotland. So, we keep a very close eye on the crop, checking it two or three times a week.

“Slugs aren’t normally much of a problem on these soils, and although we do get flea beetle shot-holing, it’s nothing like growers down south have had to deal with. The larvae don’t seem to get into the stem and the crop powers through.”

Late drilling means plants are still relatively small going into the spring so weed competition can be an issue. To guard against this, the crop gets a pre or early post-emergence mixture of metazachlor with either clomazone or quinmerac. An autumn graminicide is often needed for barley volunteers too.

Spring fertilisation consists of two dressings of Axan (27% N + 9% SO₃) or Sulphan (24% N + 15% SO₃) followed by one of Extran (33.5% N) to ensure the crop gets the sulphur it requires.

“Tissue testing has also shown that molybdenum and boron are low, so we apply these at stem extension,” Mr Anderson explains. “And we find extra magnesium at flowering really helps too.

“Because DK Exsteel has a strong 7 for light leaf spot resistance, an application of Kestrel (prothioconazole + tebuconazole) keeps the disease well in check ahead of flowering.  With the extended flowering period, we’re keen to ensure the crop is kept green, as well as covering the risk of sclerotinia. So, we go back in with a relatively robust mid-flowering application of Kestrel plus azoxystrobin.

Even though oilseed rape is not widely grown in the area when potatoes are in the rotation, the Milton of Mathers team see it as an important part of their regime. “Providing we grow a variety with plenty of get-up-and-go from later drilling, we’ve shown that crop fits well as an extra cereal break after spring barley,” Mr Anderson stresses. “DK Exsteel is one of the strongest here and it is doing us a great job. “We also really benefit from the hybrid’s ability to branch out to even-up the canopy. It matures slowly, but we’re in no rush because of the long days; and by building the right canopy we know it rewards us well.

“A history of neep-growing does means many soils up here are prone to club root. But keeping the crop on a wide rotation means we don’t need to sacrifice yield by growing a resistant variety.”