Why data is proving useful in one grower’s blackgrass battle

Precision agronomy is helping a Cambridgeshire grower and his agronomist fine-tune blackgrass control and improve farm performance.

Having taken the plunge and linked his precision farming data with agronomic practices and management decisions, grower Harry Horrell is now able to interrogate multiple layers of information.

Over the past five years, other changes to help reduce grassweed populations made at C Horrell at Thorney, near Peterborough, have included the introduction of a shallow cultivations regime, delaying wheat drilling by a month, and the use of variable seed rates.

See also: Undersowing maize with grass brings soil health benefits

There has also been strategic investment in drainage and the roll-out of a strict machinery hygiene policy at harvest.

At the same time, spring crops have been investigated for their contribution to weed control and maximum use has been made of the farm’s data, with the Omnia system allowing in-depth analysis of fields from a multi-layered approach of connecting farm data with agronomic decisions.


Harry Horrell pays a subscription fee per hectare for Omnia and points out that it is an additional cost to the business.

Having started his precision farming journey with yield mapping, he now has a system which has added to his knowledge and understanding and allowed him to make good use of his farm information.

“You get out of it what you put into it,” he says.

Yield lift

For Mr Horrell, the integrated strategy has meant there has been steady progression, with average wheat yields rising from 8.6t/ha by more than 1t/ha and a positive effect on the bottom line.

“We’re not chasing yield at any cost,” he says. “We’re focussed on profitability. The ability to explore data from the past six to seven years has allowed us to understand much more about individual field performance and where we can make worthwhile improvements.”

Joining an AHDB benchmarking group has also helped, he says, making him more aware of costs and helping to pinpoint areas for improvement.

His agronomist, Andrew Buckberry of Farmacy, has worked with him during this time, so that their combined knowledge of the farm is exploited.

As a result, what were large areas of blackgrass have now been reduced to isolated patches in fields, which can be targeted with an appropriate herbicide programme.

Data layers

Mr Buckberry also ensures that the results from various sources of data – such as yield maps, drone images, plant establishment counts and normalised difference vegetation index (NDVI) pictures – which feed into the Omnia system, are interpreted and converted into recommendations for the farm team to implement.

“We can’t let blackgrass dictate how we farm, but we can manage it on a field-by-field basis,” he says.

“The more we understand about what’s going on, the easier it is to remedy, which is where Omnia comes into its own.”

He believes the precision farming technique which has made the biggest difference to the business is variable seed rates. This is because it has allowed them to take account of soil type, pest and weed pressures, germination percentages and any compaction or soil structure issues.

“Variable rate seed maps have been a step forward. With the layers in Omnia, we know where the blackgrass is, where any wet-lying areas, are and the likely threat from pigeons and slugs, as well as the yield potential of the field.”

© Tim Scrivener

Plant competition

Being able to alter seed rates accordingly has given even establishment and helped to produce a more competitive crop. Wherever possible, wheat varieties that tiller strongly are chosen, and seed rates will only go as high as 500 seeds/sq m if it’s deemed necessary.

Plant establishment counts are carried out and recorded, so that seed rates can be fine-tuned, while drainage maps have been added to the Omnia platform to help with this task.

Herbicide use has been reduced on the better fields and costs are coming down, reveals Mr Buckberry.

“Flufenacet is the basis of our pre-emergence spray with any post-emergence top-ups being really targeted. The more insight we have from Omnia, the more we are able to save money on sprays.”

Expert view

Producing a uniform, competitive crop across a variable area is a fundamental part of a blackgrass control strategy, stresses Gordon Anderson-Taylor of Bayer.

The difference between a good crop and a thin one can be as much as 50% of blackgrass control, as the weed’s tillering capacity and seed return is reduced, which is why variable seed rates work so well.

“It’s all about crop competitiveness,” he says. “Of course, we also want an economic crop with a good yield, so it is possible to go too high.”

Precision application of herbicides using variable rates is more difficult to do, he notes, as there are still some serious challenges with weed detection to be overcome.

“It’s more appropriate to apply a robust pre-emergence programme across your entire wheat area and then adopt a more targeted approach to the peri-emergence treatment,” he advises.

Otherwise, delaying drilling by a month, introducing spring cropping into the rotation and managing the seed bank are all effective measures and should be part of an integrated approach.

“Harry is doing all of these things and continues to fine-tune his strategy. Technology is moving fast and is now offering innovative ways to battle blackgrass – so it’s not just about herbicides”.

Rotational changes

A fairly flexible rotation has allowed Harry Horrell to try out some different spring crops over the past couple of years, as he moves away from growing second wheats.

He is also reconsidering the place of oilseed rape, given the pressures that the crop has come under, and doesn’t believe that the current sugar beet crop has a long-term future on the farm.

“Spring wheat has worked well and hasn’t created any storage issues,” he reports. “But having grown spring barley this year, we got higher yields and better blackgrass control from it.”

Spring linseed and canary seed are also being put through their paces this year. Both have given good blackgrass control – not from their competitiveness – but from their later drilling dates and the chance they give to get a good chit ahead of drilling.

Getting started

If blackgrass is threatening farm productivity, the first step is to make sure that you have mapped it, advises Nick Strelczuk, precision technology specialist with Hutchinsons.

Once that’s done, variable seed rates can be introduced cost-effectively – for as little as £300 in some situations – and have shown to bring a 0.6t/ha yield benefit.

“They offer other things too,” he points out. “A more even crop is much easier to manage as the season progresses, for instance.”

Having taken the first step, the next stage is to introduce plant vision, which involves taking readings as you travel through the field, by having NDVI sensors on the sprayer.

“That gives you another layer of information and allows you to create a variable fertiliser plan, targeting the nutrients to where they are most needed and according to crop potential.”

Once seed and nitrogen are being applied variably and yield maps are available, there is then an obvious progression from introducing TerraMap, as it shows what’s going on in the soil, he adds.

“It gives you high-resolution soil maps with an enormous amount of detail. These can then be overlaid with additional field information, adding to your understanding of what’s happening in the field.”

Each layer gives you more insight, notes Mr Strelczuk. “You can go at your own pace and add to the Omnia system when you are ready. It’s taken the scare factor out of precision farming.”