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Don’t overlook the importance of seedbed preparation to optimise the performance of winter cereal pre-em herbicides, growers are advised.

Even distribution over the soil and through the surface layer is essential to maximise efficacy, as this is where chemistry is designed to work.

Uneven seedbeds may restrict crop establishment and harbour black-grass seeds, NIAB’s John Cussans warns. “Poorly established crops will be slower to get away, limiting competitiveness. Seed-to-soil contact is another reason to invest in preparing a good seedbed.

“Also, clods will insulate black-grass seeds from pre-em chemistry. Small islands of black-grass will emerge as clods break down and seeds germinate.”

If a quality seedbed cannot be achieved, he and colleague Colin Peters question whether it is worth sowing a crop.

“It’s not just that season’s crop that will be compromised, but you will potentially create a stronger weed burden going forward. It might be better to step back and reset the plan,” Mr Peters suggests.

Attention to detail is needed across the board, adds Hutchinsons’ Dick Neale, who says an even seedbed is more important than a fine seedbed, as fine seedbeds can slump or cap.

Pre-em herbicides need moisture to activate, so anything that prevents even coverage across the field surface will lead to inconsistent weed control.

Drill setup

Attention to detail is important with cereal sowing depth too. Aim to ensure seed sits at an even depth, particularly avoiding seeds being drilled too shallow. To ensure crop safety, winter cereal seed should be sown to at least 35 mm.

For Mr Neale, drill setup should be on a field-by-field basis. He says soil condition following a broad-leaved crop like beans and peas will be unlike that of a previous cereal crop. “Their root structures will be totally different and seedbed friability impacted, so drilling strategies need to be tailored accordingly.”

Where soil needs to be worked, growers should consider where grass-weed seeds are in the soil profile. He sees two options; bury seed to prevent emergence, or leave it near the surface to chit pre-delayed drilling.

Either way, the objective must be good movement of moisture and herbicide through the soil surface, and prevention of ponding in the seeded zone. He also recommends rolling soon after drilling to minimise moisture loss and maintain even seed depth.

Min-till strategies do not worry Mr Neale, but he says it is essential to create a ‘trash-free’ strip of soil. “Trash will impair pre-em movement to the soil surface and no drill is going to work to its optimum if it is having to work through an extensive layer of trash. Seed placement is often impacted, increasing the chances of seed being placed in the activity zone of the herbicide.”

 

Build soil health

Philip Wright of Wright Resolutions says manufacturing a seedbed will do a job, but there is no “quick fix” for soils and seedbeds. To optimise long-term crop performance and pre-em efficacy, a natural, biologically active seedbed is the better option.

He feels a soil that can sustain itself will help sustain everything else, with minimum or no-till being useful.

“It isn’t just improved movement of water or pre-em chemistry through the soil, but nutrient availability, rooting and weather resilience. It’s giving crops the best possible chance. Also, you’re not having to do the same level of mechanical structuring, so there are cost and time benefits.”

Those with heavier soils or root crops in the rotation may question reducing steel through soils, but Mr Wright says developing resilient soils will help them “bounce back” quicker.

“Obviously certain soils are more suited to low-inversion or no-till practices, but it doesn’t mean soil structure cannot be improved.”

Short-term yield loss is possible, but longer-term, the benefits will be seen. “You can only gain by removing barriers to water, nutrients and air through soil where they exist.”

He suggests starting with farm rotation, introducing strong rooting crops or crops that can be sown with minimal soil disturbance to help offset problems caused by root crop harvesting.

“A repair crop can help recovery, and well managed cover crops have a part to play more generally.”

This creates the ideal environment to start to reduce tillage depth, he adds.

 

Key messages

  • Even, clod-free seedbeds improve pre-em efficacy
  • Soil moisture is key
  • Tailor drill setup to field conditions
  • Focus on improving long-term soil health

 

This article is an extract from CropFocus magazine, if you would like to sign up for the next issue please sign up here

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