Farmers Weekly Direct Talk on…Weeds expert Dick Neale claims min-till won’t worsen grassweeds. Indeed, pointing out that non-inversion tillage (NIT) is a better term than min-till, he says:

“NIT is often blamed for increasing grassweeds, so rotational ploughing is still widely employed. In my experience, this is misguided because well-executed NIT does not raise grassweed burdens.”

But what did you think? Here’s some of the debate and responses your posts elicited.

Bill Davey: New research here in New Zealand recently confirmed that the burning of stubble actually increases crop yields, helps reduce weed and pest pressure, and contributes significantly to fuel and labour savings.

Reducing agrochemical costs by as much as £30/ha was achievable, as well as cutting cultivation costs by almost £16/ha.

I have witnessed several English farmers revert to burning stubble, although adamant upon first arriving in New Zealand that they would not burn.

I suppose it helps our cause that there are only 4m folk down here in comparison, and we don’t have a motorway network either. But we do have a Green Party!

Dick Neale: Using burning as a rotational tool would be very helpful…but we can’t, so that’s that.

The important element of NIT is remaining flexible and having the ability to react to seasonal variation in weather…and to react fast.

David Greasby: I am convinced that ploughing in many situations is still the best option for grassweed control, albeit the final seed-bed from any cultivation strategy has greater implications, not only for successful germination of any crop, but also on the range, timing opportunity and type of spray used to deal with grassweeds.

Dick Neale: I am not totally anti-plough, as in many medium/light soils it is still the most effective (and cheapest) cultivation system available. My real issues with ploughing in heavy soils, which tend to carry the worst grassweed burdens, are as follows:

• Too slow and expensive.
  
• Move to wider furrows gives poor inversion and poor seed burial.
  
• Poor seed-bed quality which compromises pre-em efficacy.
  
• Ploughing is a skilled operation. That skill is often lacking on farms with temporary labour at peak times. Un-level ploughing with poor trash burial is becoming a real problem.
  
• Poor final seed-beds give increased slug problems and cost, poor establishment and, therefore, poor crop competition with grassweeds.

John Cussans: We need to think about what is happening to the weed population in both ploughing and NIT approaches.

It’s back to basics: The seed bank of weeds exists effectively in two parts – a deep part where seeds will not successfully establish, and a shallower part from which seeds can establish.

In a ploughing system, the aim is to move as much of the seeds as possible into the deep part of the seed bank and harness the process of seed death that occurs each year (for blackgrass something like 60% of the seeds will die of natural causes each year).

In a NIT system, all the seeds are kept in the shallow layer, as the aim is to stimulate as much of it as possible to germinate (for example, with false or stale seed-beds) and then kill them (with cultivation or herbicides).

Can a non-inversion approach match the efficacy of ploughing? Yes, but only if you maximise the stimulation of germination AND the effective control of plants that do germinate.

I think that sometimes the approach has got itself a bad name because people forget that the tillage (which is the “headline”, if you like) is actually only a part of a package and the whole thing needs to be right.

Dick Neale: My basic rule of thumb is work no deeper than 100mm with NIT surface cultivations. Worms are the vital component in making the system work over time and the deeper you work, the more you potentially kill.
As oilseed rape continues to grow in importance, so does the opportunity to use propizamide and carbetamex for grassweed control. Both of these products work on seed germinating from shallow depth.

“Why spray every weed? Overall, it seems the level of weed control (and hence herbicide use) is too high to be justified purely on economics. Why are almost 100% of arable fields sprayed with herbicide – often more than once?”

Steve Bumstead: I would dearly love to spray once, but I get the little problem of subsequent flushes of weed growth.

John Cussans: What sort of weed species do you get merging late and how late compared with the crop sowing date – if they’re emerging much later than the crop in your spring barley, do they really represent a threat to your yields?

James Stafford: You need to target a very broad spectrum to control as much as possible. If you have the majority of weeds under control, rates of certain products can be cut back slightly.

John Cussans: OK, so broad-spectrum weed control is your strategy. Are you paying a premium for that control, over and above what it would cost just to target the priorities?

Are you using pre-harvest glyphosate to desiccate for harvesting reasons or as a herbicide? If for the latter, what is it costing you to control (what I assume to be a really quite low density of) groundsel?

I guess my question (for most growers) is: Has the change in the economics of crop production (post-SFP) changed your attitude to weed control?

Mark Ireland: I agree that it isn’t necessary to clean out 100% of weeds present in a crop, but it takes a brave man to make the decision, which could mean you’re either agronomically and financially astute, or the local laughing stock.
What about the carry-over of pests and diseases in weeds, especially with the advent of the entry-level scheme and over-wintered stubbles?

Sponsor’s comment:Adopting integrated control strategies for sustainable weed control over the next 10 years is vital to protect and optimise existing chemistry. Weed focus aims to engage the industry to discuss, develop and share knowledge, expertise and current thinking for improving grass and broad-leaved weed management through best practice. *Direct Talk on…Weeds is brought to you in association with Weed Focus, the initiative from Bayer CropScience. Join the continuing debate on our forums and for more solutions on your biggest weed “headaches”, go to Weed Focus. …