Cultivations

1. There is conflicting evidence regarding the role of ploughing and minimal/no tillage for controlling black-grass. Can we define the strengths of each?

Opinions and research on the value of ploughing versus minimal tillage for controlling black-grass vary and no one answer suits all situations.

Each method has its own merits and drawbacks, as summarised in the table below. Success of any system often depends on the individual farmer and/or machine operator’s ability to understand the challenges and make the chosen strategy work, says Mr Cotton.

Acknowledging the diversity of soil types and farming situations in the UK, Mr Drinkwater adds: “They key is to understand what works on your farm, choose a system and stick to it.”

 

Ploughing

Min/no till

Strengths

Burying seed provides a “clean start” or “reset button” for following crops

Keeps seed close to surface where it can germinate and be controlled

 

Allows natural degradation of black-grass seed – around 70% a year

Minimising soil disturbance avoids bringing fresh seed to surface

Weaknesses

Risks bringing-up old weed seeds from previous years – need to know where seed is within the soil profile

No clean start from burying seed to depth – potentially high population pressure from the start and more pressure on chemistry

 

Has to be done well to bury seed properly – late ploughing in bad conditions may exacerbate problems

Practical challenge to keep cultivation depth to a minimum

 

Slower and more expensive process – may also reduce natural soil structuring

Possible issues with reduced pre-em efficacy on trashy seedbeds?

2. How often should we plough if that method is chosen?

Again, there is no right or wrong answer for all farms. Some may choose to plough occasionally as a “reset button”, while advocates of minimal/no tillage may not want to undo improvements to natural soil structuring by reverting back to the plough.

Agrii trials suggest rotational ploughing once every five years with four years of shallow cultivations in between could provide an effective solution in many situations.

Good ploughing early in the autumn provides a relatively clean start for the following crop by burying any seed returned that season, explains Mr Lloyd. Minimising cultivation depth in subsequent years then keeps black-grass seed within a kill zone for chemical and cultural control.

“But, whatever cultivation system you use, delaying drilling makes a huge difference to black-grass control.”

The past 15 years of trials at Agrii’s Stow Longa show the last autumn black-grass emergence is typically around 2 October, he notes. “For the worst fields I wouldn’t drill before mid-October, as the worst of the black-grass has to come out before the drill goes in.”

3. Heavy soils can be very challenging when very dry or wet. What should we do if moving from a min-till system with rotational ploughing to a strip/direct drill system?

Patience is the key to working heavy land, regardless of how it is done, says Mr Drinkwater. “Don’t do anything until soil conditions are right - land will dry out eventually. You can’t force the situation, especially with min-till or direct drilling systems.”

Examining soil structure and addressing structural issues (such as compaction, poor drainage or lack of organic matter) is essential, adds Mr Lloyd.

He, and others, believe growers should retain some flexibility in their cultivation/ establishment strategy so it can be tailored to individual seasons, soil types and crops. Selling all old kit for a wholesale switch to one type of system may not be the best option, although they acknowledge retaining such flexibility comes at a capital cost.

Land prone to compaction should be treated carefully, especially at harvest, to avoid creating structural problems, notes Mr Drinkwater. This may mean avoiding running tractors and trailers over the field and keeping combines to tramlines. Reducing tyre pressures or running machines on tracks may also help.

4. What is the best cultivation strategy to turn around fields in autumn to maximise yields and minimise black-grass? What machines should we use?

As mentioned above, there is no one-size-fits-all answer. Research suggests rotational ploughing one year in five may be an effective strategy and many experts support this view.

However, every farm is different so choose a system that works for you.

Some top tips include:

  • Prepare seedbed early by cultivating in good conditions – then leave alone
  • Delay drilling as long as possible until most black-grass has emerged
  • Spray off seedbed with a robust dose of glyphosate
  • Drill crop and minimise soil disturbance when doing so
  • Avoid any further cultivations before drilling (likely to bring-up fresh black-grass seed that will emerge within the crop)
  • Ensure good seedbed consolidation
  • Adapt strategy according to field conditions – be prepared to delay drilling or switch cropping if necessary on worst fields.

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