Spring cropping has a key role in tackling blackgrass, but which are the best crops for tackling the weed and maximising returns?

Four years of trials data have come up with some pointers on spring crop success.

With the right approach, spring crops can deliver the best gross margins on farms in bad blackgrass areas, while also breaking the cycle of high weed seed returns.

Even in the poor spring crop season of 2018, they delivered the highest margins in Agrii’s trials on a Cambridgeshire farm, outperforming winter wheat.

Spring cropping is a key tool in the fight against blackgrass and some farmers are looking to grow three to four back-to-back spring crops in order to break the cycle of blackgrass seed being returned to the soil.

See also: Expert advice on using rotations to tackle blackgrass hotspots

However, there are greater risks with spring cropping compared with winter-sown crops. So how can farmers minimise the risk and make the most from spring cropping?

Agrii’s trials manager Steve Corbett looks at some of the lessons learned from four years of trials data.

Agrii trials manager Steve Corbett

Cultivations

The most important factor, according to Mr Corbett, is setting soils up for the spring.

“Farmers need to consider what cultivations are needed in September to set the soil up for spring drilling. Consider what depth to cultivate to and don’t forget the press. Then leave it over winter.

“The key driver is that you don’t want to have to re-cultivate in spring, as that will stimulate blackgrass flushes.”

He points to some farmers who tried growing spring wheat only to find they had a worse blackgrass problem than in winter wheat.

Ideally, whether farmers have a disc or tine drill, they just need to plant the seed and not move the soil.

Keeping soil movement to a minimum also helps conserve moisture, which was essential this season with the summer drought.

In considering what cultivations were needed this summer, Mr Corbett had to tackle soil compaction at the Stow Longa trials site.

Last spring was extremely wet and he calculated that the extra water equated to 600t/ha and this additional weight caused some compaction.

“About 5in down we were getting a dense compaction zone because of the washing down of silts.

“So we had to get rid of the compaction, as it would affect spring crop rooting next year.”

That’s because spring crops need to move quickly. “You have to get everything in place for the crop to grow at the maximum rate, especially with blackgrass in the background.

“Crops have got to be quicker than blackgrass to be competitive,” he explains.

Which crop?

Another key question is – which crop? It has to compete with blackgrass and deliver a return.

Spring wheat is an obvious contender, but it has proved to be uncompetitive in a bad blackgrass situation.

“Its lack of competitiveness was made worse in the challenging conditions last spring, as it was drilled late and it didn’t tiller.”

He has found that seed rate is key and has taken a variable-rate seeding approach. In bad blackgrass patches, rates have been pushed up to 700 seeds/sq m while in more normal areas he aims for 400-450 seeds/sq m.  

Ergot and gout fly are other issues affecting spring wheat.

The weakness of spring wheat in bad blackgrass areas is borne out in the gross margin figures.

Looking at the average over the past two seasons (see table), spring wheat is the poorest performer and also has the highest amount of risk, with some plots delivering just £47/ha in 2018.

In contrast, both oats and barley are better in terms of competitiveness.

“Given perfect conditions in a glasshouse, spring barley is most competitive. However, in the field and under tougher conditions, spring oats comes top.

“One reason is that oats have a stronger cotyledon and are, therefore, more capable of punching through any smearing of soil at drilling.”

Spring barley is Mr Corbett’s default choice. “In fact, spring barley after spring beans gave the highest margin of £936/ha.”

New barley © Tim Scrivener

But if it is looking like a tough season, oats will be less risky in the more challenging fields.

However, he points out that oats need to be grown on a contract to achieve the required margins. In the trials, they grew Elyann for milling and barley was also on a brewing contract.

Importance of variety

Speed of development is key in the early phase and for barley, Explorer and Planet are quicker starters, while Sangria is slower.

The late spring of 2018 highlighted the importance of variety. Mr Corbett managed to drill some Sangria barley on 22 March before the weather turned.

It wasn’t until 27 April before the rest could be drilled and he switched to Explorer, being a quicker starter.

Interestingly, the later-drilled Explorer outperformed the early-drilled Sangria, delivering 5.65t/ha compared with 4.83t/ha.

“It showed that delaying drilling paid off rather than mauling it in,” he says.

 “You need to go by the conditions rather than date and then be flexible with variety choice if conditions change.”

Drilling date

Date-wise, Mr Corbett aims for around 15 March, but again 2018 showed that farmers should go by conditions and not calendar date.

He advises farmers to go out into the field and check conditions with a spade.

Soil friability in the drilling zone is key and the drill needs to flow through without any smearing and slotting.

Nutrition, PGR and weeds

Again it’s all about getting crops off to a rapid start and then keeping the crop going, as spring crops have such a short season.

Putting fertiliser down the spout is valuable, “as you don’t want the crop to stop growing and start looking for nutrients”.

Mr Corbett aims for 60kg/ha of N in the seed-bed and then the rest on by growth stage 12.

For the level of performance needed, he aims for a total of 150kg/ha N. High grain nitrogen is not a problem, as the barley is destined for specialist brewing.

With grassweed control, Mr Corbett would rather invest in nutrition and get crops moving rather than focusing on pre- and peri-emergence applications of diflufenican + flufenacet. “There is a risk that crops can stall.”

He also aims to get a couple of plant growth regulators (PGRs) on, as Explorer can brackle and an early application will also help promote tillering.