Direct Talk on...Weeds expert Dick Neale says ...

If a grower tells you they plough then you know exactly what you are dealing with.

If they “min-till”, that can mean anything from spread and scratch to 36cm (14in) of soil being moved with a Simba Solo - and that’s not my idea of min-till.

So let’s dispense with the min-till label and call it “non inversion tillage”.

Integrating cultural and chemical practice is not hard, but it takes planning and forethought.

The key implement in non-inversion tillage is the drill as it dictates preceding cultivations which in turn influence weed germination.

Non-inversion tillage is often blamed for increasing grassweeds so rotational ploughing is still widely employed.

In my experience this is misguided because well executed non-inversion tillage does not raise grassweed burdens. However, poorly planned and conducted it does complicate control.

Non-inversion tillage gives you time to manage your problems correctly. But you must identify your problems first.

For example, some brome species germinate in the dark. Others need light and heat - plough these down and you’re in trouble.

It’s worth remembering the impact of different seasons on weed seed dormancy and that herbicides only kill what is growing. So cultivations that induce dormancy will work against them and lead to poor control.

I’m not sure my observations, as a direct comparison with the British farmer, are really relevant, but thought they might be of interest.

New research by the Foundation for Arable 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.

Having farmed through the years of burning being both permitted and banned in England, we noticed a serious weed sugar beet infestation once burning was banned.

In a world seemingly determined to reduce the burning of fossil fuels, how unfortunate it was that Great Britain’s urban majority found this invaluable husbandry technique so environmentally unacceptable.

Straw and crop residue burning is alive and well here in New Zealand and without doubt the most invaluable tool farmers have when it comes to establishing crops without ploughing.

It is a subject I feel passionate about in so much that the Kiwis take it for granted that they will be able to continue to burn for years to come, and what’s the problem if a few hedges catch fire. Admittedly that is not the view of them all, just a minority, but they are the ones that catch the public’s attention.

Soils here, especially on the Plains, are so friable that when depleted of moisture, which is often the case post harvest, it is impossible to mix soil and chopped straw efficiently. I have witnessed several English farmers revert to burning stubble, although adamant upon first arriving in New Zealand that they would not burn.

If New Zealand were to lose the right to burn, then cultivation techniques and the cost of establishing crops would take on a whole new meaning. We must ensure, as farmers, that we do all we can to preserve this right.

I suppose it helps our cause that there are only four million folk down here in comparison, and we don’t have a motorway network either. But we do have a green party!

On the whole I think Ben has covered the Direct Talk topics really well.

We have a predominantly plough-based system up here which overcomes a lot of the issues. We only min-till for oilseed rape.

We do have a bit of blackgrass in one field which I think came in with some wheat seed. We’ve nobbled it hard with Roundup and we’re going to be very careful with that field from now on.

With the current trend towards minimum tillage should we continue to reduce overall spray usage and deal where possible with weed problems culturally - or does this concept exacerbate grassweed problems to such an extent that  increased costs could negate the advantages of minimum cultivations?

I am convinced that ploughing in many situations is still the best option for grassweed control albeit the final seedbed 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?

Are there any thoughts or research information relating to potential problems of weed build up under a continuous minimal cult operation and, indeed, whether there is an optimum minimal cult/plough ratio that should be considered in our management – is this relevant? (eg 3 years minimal cults:1 year plough)

Thanks John.

By the way everyone, the Ben referred to is Ben Atkinson, one of our Farmers Weekly barometer growers. Ben kindly provided some initial thoughts on our experts' comments in Farmers Weekly 15 September issue.

Julian

It would be nice to have the flexibility that Bill now enjoys. Useing burning as a rotational tool would be very helpful ...but we can't so thats that. The important element in NIT (non inversion tillage) is remaining flexible and having the ability to react to seasonal variation in weather ...and to react fast.

Burning would have been inflexible this season in the UK. I would not have confidently lit fires in late July! and the matches would have been a bit wet in August leaving acres of unburnable straw and intolerable delays in cultivations and sowings.

David

The primary use of the cultural element in weed control is manipulating dormancy and promoting rapid germination pre cropping so that glyphosate can be used effectively. This is where massive savings can be made in the overall programme cost and crop yield can be enhanced because of removal of early competition. Cultivations alone transplant more weeds than they control or control weeds via dessication by drying out the growing environment (seedbed) ...problem with that is the newly planted crop then has no moisture with which to germinate.

NIT to a maximum of 4" depth keeps all recently shed weed seeds near the soil surface, in friable tilth where moisture can be preserved via a pressed or rolled finish.  This means that you know the location and quantity of seed return and the seasonal effect on dormancy. What you don't have is the unknown quantity of grassweeds ploughed up ..and this is what occures with rotational ploughing.

Dick,

I think discarding the 'min-til' label (which covers a multitude of sins) and starting with a clear definition of the approach as 'non-inversion tillage' is exactly right.

I'm not a fundamentalist as far as taking an inversion of non-inversion approach to weed control. Both can be sucessfull but we need to think about what is happening to the weed population in both approach. It's back to basics; the seedbank of weeds exists effectively in two parts a deep part where seeds will not sucessfully establish as new plants and a shallower part from which seeds can establish.
 - In a ploughing system the aim is to move as much of the seed as possible into the deep part of the seedbank and harness the natural process of seed death that occurs each year (for black-grass something like 60% of the seeds will die of natural causes each year). This also has the effect of (hopefully) reducing the number of seeds in the shallow layer and hence the number of plants that will establish in the crop.
 - In a non-inversion system all the seeds are kept in the shallow layer as the aim is to stimulate as much of it as possible to germinate (e.g. with 'false' or 'stale' seedbeds) 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 one part of a package and the whole thing needs to be right.

I'd make a couple of comments if I might
- It seems inherent in a non-inversion tillage approach that although total seedbank numbers may be the the same or even lower the numbers of seedlings that establish is inherently higher - hence putting more pressure on getting control exactly right.
- My own prefence would be for some sort of (carefully planned) rotational ploughing to make use of both strategies to reduce the weed seedbank.

Sorry for the length of this post!

John

John, thanks for your comments. Broadly speaking we are in total agreement. I have been asked to focus on the nit issue but 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 do tend to carry the worst grassweed burdens, are as follows:-

1. Too slow and expensive
2. Move to wider furrows give poor inversion and poor seed burial
3. Poor seedbed quality which compromises pre-em efficacy
4. Ploughing to a high standard is a skilled operation and as farms grow with temporary labour at peak times, that skill level is often lacking ...unlevel plouhing with poor trash burial is becoming a real issue. 
5. Poor final seedbeds give increased slug problems and cost, poor crop establishment and therefore poor crop competition with grassweeds

Dick

Dick,

A question for my own illumination - From your perspective doesn't this strategy (N-I-T) on heavy soils due to the ground conditions run an increased the risk that opportunities for false/stale seedbeds (vital to the sucess of the approach) are not available?

The point about the effectiveness of ploughing in practice I 100% agree with - all the theory is based on effective inversion down to 30cm (well perhaps that's over-stating it a little). Some of the ploughing that's practised is non-inversion tillage by another name with all of the costs of ploughing but none of the (potential) benefits.

I wonder do slugs eat weeds as well?

John

John,

From my perspective the very reason I encouraged my clients into as near total N-I-T as possible is the ability to create stale seedbeds in almost all seasons and retain the key elements of good tilth (that produced by nature over the year), and moisture within that tilth. The biggest issue is demonstrated clearly by the use of  the cultivation technique centre page in our article in FW, ...a set of discs working too deep with no form of consolidating press or rolls attached.

Dick

Yes non-inversion tillage (NIT) is the term I prefer because if you subsoil, disc, spray disc and till that ought to be maxi-till, not min-till!

NIT doesn’t need to increase grassweeds but it will if not executed properly.

Farmers need to consider what they’re trying to achieve: Avoiding yield reduction, saving time, and hopefully money. Common questions are: How deep do I need to cultivate? How much soil do I need to incorporate the straw? Also remember one method will not suit all the situations on the farm.

The most important piece of non-inversion tillage equipment is a spade to check what cultivations you need to do and to check that you’ve achieved the right result. Bear in mind if there’s lots of straw, you may need to go deeper to incorporate it thoroughly.

With NIT there is greater potential for problems, but with thought they can be avoided.

Make sure volunteers and grassweeds have actually emerged, and also remember the min-till-type drills are much faster, so you don’t have to be in so much of a hurry to get drilling done...you can wait for grassweeds to emerge.

Key is keep pressure off the herbicides. Do as much as you can culturally.

Heavy soils benefit the most? Yes I agree. The organic matter inclusion benefits soil structure very quickly. Year after year you can work a bit deeper to improve it at greater depth say 4-6 inches but not 12 inches as in ploughing.

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 your potentially kill.

Straw only needs some soil contact to induce decomposition and the worms will do the rest overwinter, pulling the straw down to depth ...they are very active little creaters if you give them a chance.

All the drills designed to work in a NIT system prefer working in a good base of soil at sowing depth and loose soil mixed with lots of straw is not helpful.

As 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. Deep cultivation and mixing of seed only works against both products and represents a missed opportunity.

Dick

This is an old thread, but I am a newcomer.  In the USA, when we gave up the plow, we got more weeds, especially grass weeds.  I have only skimmed these posts, but it appears that you till more in the UK.  Generally, we do not burn our straw either........but on my own farm I never follow wheat with a winter cereal, always with corn or soybeans.  Here, whenever we get a weed problem in a field that we just can't beat, we get the plow out of the shed and plow it.  Maybe it just makes us feel better, but I think it helps.