NIAB - National Institute of Agricultural Botany

Orson's Oracle

A poisonous past?

Posted on 02/07/2013 by Jim Orson

Well, the UK Government has certainly thrown its weight behind GM. I cannot disagree with any of the arguments made but creating a clear picture of the advantages of the technology is not easy.

The reason I say this is because I learnt a lot about the boll weevil on my recent visit to a cotton plantation in Louisiana. This insect invaded the US cotton belt at the turn of the 20th century and all but ruined the industry.  It is estimated that during the 1920s and 1930s it reduced yields by around 50%.

Dusting Machinery for Cotton Boll Weevil ControlIt became nationally important and folk songs were written about it. Cotton farmers soon started to treat the crops with insecticides to try to control it. This was initially dusting the crop, by hand (see picture) or by horse driven machinery, with arsenic based salts that often included lead.

Then DDT was used and after that the organophosphates and then the pyrethroids were adopted. At one time, up to 15-20 insecticide applications a year were being made and weevil resistance to them was building up. It was in the late 1970s that experimental eradication zones were tested and this initiated the national eradication programme.

The eradication programme includes federal legislation stating that only registered growers who agree to take part in the scheme can grow cotton. Crops are monitored using pheromone traps and are only treated when necessary. This has resulted in the recovery in the number of natural predators. Farmers pay 70% of the cost of the programme and the federal government the remaining 30%.

The boll weevil originally came into Texas from Mexico in around 1892 and then spread across the cotton growing states. The eradication programme has successfully reversed this progress, starting at the extremities of its spread and gradually pushing back the pest to Texas. Now many states are free from the pest.  Texas and Northern Mexico have become the front line. The pest is more able to hang on in these areas because the very mild winters mean that volunteer cotton plants survive and host the pest during the summer. So, volunteers in other crops and also in roadsides and field edges are now destroyed.

There have been set-backs in these areas. Hurricane winds have blown the weevil into districts previously free of the pest. Hence, monitoring continues in the weevil-free states. Also the activities of drug trafficking gangs on the Mexican-Texas border have limited the ability of the field workers to monitor the pest!
A measure of the success of the eradication programme is that overall the average number of insecticide applications in the crop has been reduced from 15-20/annum to around 2.8.

GM Bt cotton to protect the crop from weevil was first introduced in 1996 and now has a market share of over 70% of the area sown. So can all the reduction in insecticide spraying be claimed as being the result of its introduction?

There are two ways of looking at this. The eradication programme was introduced and was making good progress before the introduction of Bt cotton. Hence, claiming that all the reduction in insecticide spraying is due to Bt cotton is open to dispute. On the other hand, resistance to the synthetic insecticides was increasing and without the additional intervention of Bt cotton this may eventually have led to a break down in the programme.

I suppose there is another alternative to Bt cotton in combating the increasing resistance to the synthetic insecticides. The industry could return to the ‘good ol’ days’ when the ‘natural’ insecticides based on arsenic and lead were used. Given the choice, I think I would not be alone in preferring the Bt option.

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What's new?

Posted on 24/06/2013 by Jim Orson

‘What’s new’ is a question frequently asked by farmers, advisers and the press at field events.  I was certainly asked it several times last week at the Cereals Event.  The inevitability of being asked the question means I should really have a prepared response; I never have.

Jim Orson at Cereals 2013

The technical nature of the industry means that everyone wants to be up to date. This is understandable but I think the real question being asked is ‘is there a miracle product or technique around the corner that will really lift productivity’? In the late 1970s and early 1980s the answer to that question was affirmative. We were being swamped with new approaches and products and the Cereals Event was established to showcase them.

So what should have been the answer to the question last week? Much of the ‘new’ introductions or initiatives are very much re-packaging current knowledge or pesticides. This gives the impression that the industry is furiously paddling away just to stand still.

It is my firm belief that the only way for real change is to look for step changes in plant breeding. One approach is GM and the Cereals Event has a history on this. Just over a decade ago, a demonstration plot of GM sugar beet was pulled up by those whose perverted sense of democracy is the right to destroy anything with which they disagree. It now seems that the politicians are realising that the spurious slurs on GM are totally unfounded and so I hope that in the near future we will begin to see GM introductions being displayed at Cereals. That would really be a new technology of promise to discuss.

However, other things are happening on the wheat breeding front. The synthetic wheats on our NIAB TAG stand seem to have promise, with yields in some trials being significantly above expectations. Of course, anti-technologists see a threat in synthetic wheats. This is really a comment on their lack of understanding rather than an indication of any real concern. I think some are linking synthetic wheats to GM which is a testament to a lack of understanding.

Synthetic wheats are the result of reproducing the chance crossing between wild grasses 10,000 years ago thatCrossing goatgrass with durum wheat to create a synthetic wheat created wheat as we know it. Since that chance crossing, we may have lost traits that could be of real significance in today’s production systems. Also, I assume traits that were lost in the chance crossing may be retained in the reproduction of that chance crossing. So it is important to investigate thoroughly the potential of synthetic wheats and hope that any resulting valuable traits can be transferred into modern varieties.

I know I’m being a bit parochial by mentioning something on our own stand. However, it serves as an example of the ‘out of the box’ thinking that is required to take a real step forward rather than just ‘re-arranging the deck chairs’. Let us hope the anti-technologists, when they realise that synthetic wheat is reproducing a crossing that occurred in nature, will not sink their teeth into this research. I say this because we have all but exhausted the potential from pesticides. There may be some progress in yields from providing more accurate estimates of the nitrogen requirements of crops. There is also steady improvement in yield potential from plant breeding. However, it is the ‘out of the box’ technologies that are required for the industry to become significantly more productive in the future.  

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Burning issue

Posted on 09/06/2013 by Jim Orson

The pressure for a limited return of straw burning to aid the control of black-grass has not gone away. I’ve just written a brief data review on this as part of a more comprehensive report on the impact of straw burning on crops and cropping. Don’t get too excited; this review has not been financed by a UK organisation and looks at the potential impact of straw burning in another part of the world.

The review has taken longer than expected because nearly all the papers I have had to read were so old that they weren’t available electronically. Plus, the libraries at Defra and Rothamsted are both moving and so many of the references were in packing cases.

So I had to employ other means to get the information, including contacting the authors of papers that were published up to 30 years ago!  I also visited the Cambridge University Scientific Library where papers had to be dredged up from the very bowels of the earth.  This is a great institution - I love going there and luckily it is only a mile from where I live.

There is no doubt that burning straw will help to control black-grass.

Burning straw

Updating the model produced by a young (at the time) Stephen Moss would suggest that if, without burning, one needs 95% control from herbicides in continuous autumn cropping to contain populations, then this would fall to around 92.5% control with burning. 

Now, this doesn’t sound a lot - but look at it the other way round. Without burning you can allow 5% of the plants to survive after herbicide application. With burning this figure rises to 7.5% plants; a difference of 50%. This is roughly the same level of reduction in required herbicide control that is achieved with the cultural control method of adopting very high seedrates of winter wheat.

But, it’s not as simple as that. Straw burning breaks the dormancy (or stimulates the germination) of seed on the soil surface and so a higher proportion emerges when the pre-emergence herbicides are most active.  This is provided that the seeds remain close to the soil surface after cultivation i.e. direct drilling or very shallow tillage.  A surprisingly high proportion is buried below 5 cm where disc/tining to 15-20cm is used.

Then there is the issue of the role of crop residues to consider.

A student at Long Ashton did some pot studies which suggested that well distributed chopped straw that covered a lowish proportion of the soil surface did not affect the control of black-grass with isoproturon.  However, experiments in pots in Denmark and field trials in France suggest that as little as one tonne of chopped straw/ha lying on the soil surface and/or incorporated in the top few cms can reduce the efficacy of both soil-acting and soil/foliage-acting herbicides. The more straw - the greater the reduction.

The story is further complicated by the fact that straw ash can adsorb herbicides. This takes me back to the early 1980s when adsorption of herbicides by straw ash often explained poor chemical control in direct drilled crops.   However, experiments at the time showed that it took a few years of direct drilling and straw burning for this to become significant. So it can be concluded that ash, as a result of the occasional burning of straw, would have little impact on the activity of soil-acting herbicides.

Trials in the 1970s/1980s compared black-grass numbers in continuous winter wheat established after straw burning or baling. In a trial series over four years, where paraquat was used pre-drilling but no selective herbicide was used in the wheat, there was no difference in black-grass head numbers between the burnt and the baled plots where the land was ploughed. However, after four years where the plots were tined to 15 cm depth, there were five times as many black-grass heads in the baled plots than in the burnt plots and more than seven times as many where the land was direct drilled. 

This indicates that straw burning would have the greatest impact on black-grass numbers where the land is not ploughed.

So there is no doubt that ‘strategic’ straw burning would help to reduce black-grass populations but alone, it is not a miracle cure. However, it has a potential role as part of a long term control strategy where other cultural control measures are also employed in order to reduce large black-grass populations down to manageable proportions.

On the other hand, please remember that where background organic matter levels are low, incorporating straw on a regular basis can help to maintain a higher level of soil fungal biomass that will itself help to support good soil structure.

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Rewarding good practice

Posted on 26/05/2013 by Jim Orson

I have recently taken a renewed interest in which nozzles farmers fit to their sprayers.  On the heavy soils in East Anglia the vast majority regularly use Air Induction nozzles to reduce spray drift but when I asked the question in the Cotswolds recently, the vast majority of farmers didn’t use these nozzles. The explanation for this difference is clear; LERAP (Local Environmental Risk Assessments for Pesticides). This was introduced in 1999 to prevent short-term shocks to aquatic life caused by spray drift; there aren’t many water bodies and drainage ditches to protect in the Cotswolds.  This, I must admit, rather folksy tale demonstrates that the original LERAP scheme was a classic case of farmers being rewarded for good practice.

The scheme enabled, for many pesticide products, those who fitted nozzles which decreased spray drift to reduce drastically the width of the aquatic buffer zone of 5-metres alongside water bodies, including ditches. It also recognised that as dose (as a proportion of the label recommended dose) decreased and the size of the water body increased, reductions in the buffer zone could also be adopted. This sounds complex but the look-up tables were easy to understand and the scheme was relatively easy to adopt. It’s a pity that the original explanatory leaflet made it sound more complex than it actually was!

However, the recent EU pesticide regulations have significantly increased standards i.e. there is now less tolerance of spray drift to aquatic ecosystems. 

It became clear to the pesticide manufacturers that sticking to a maximum buffer zone of just 5-metres could mean that many existing pesticide products would not get through the 10-yearly re-registration process. So in 2011 CRD agreed to introduce interim arrangements that extended buffer zones up to 20-metres. 

What surprised me and many others was that there was no flexibility to reduce buffer zones of between 6 and 20-metres through good spray practice, dose reductions or because of the increasing size of the water body.

I have calculated the percentage area of a square field that falls between 5 and 20 metres from the field edge. I recognise that this is rather simplistic and assumes a buffer strip on all four sides; typically, the yield losses due to hedges and field side vegetation do not extend beyond 5 or 6 metres into the field and so the loss of area will directly reflect the loss of production. Field buffer zones

The figure demonstrates that it’s those farmers with small fields who will be more penalised. Some retained smaller fields to retain landscape features and biodiversity, so it seems that, in those respects, good practice is being penalised by these interim arrangements.

A brief review of recently issued authorisations for new products or re-registered products shows that wider aquatic buffer zones will be appearing on new labels. There is a pendimethalin product with a 20-metre buffer zone and straight diflufenican has a 12-metre buffer zone.

This is more than a little worrying because complex tank mixes, often containing these two herbicides, have to be adopted for black-grass control in the autumn. The time of application means that there is more likely to be water in ditches.

There are some other recently authorised products that have significantly wider buffer zones than the ‘old’ 5-metres. This demonstrates that with today’s necessity to tank-mix in order to get the job done, there is a potential for farmers to be forced into wider buffer zones or to use a more limited range of chemistry to control weeds, insects and diseases; the latter will only increase the risk of resistance developing. 

So I hope that the ‘powers-that-be’ can develop ways of encouraging good spray practice in order that these wider buffer zones can be reduced whilst still meeting the higher standards set by the recently introduced regulations.

By the way, notice my use of language. Just to remind you that nowadays active ingredients are ‘approved’ and products are ‘authorised’.

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Who killed Rocky Springs?

Posted on 17/05/2013 by Jim Orson

Jim reports from his recent trip to the south eastern states of the USA.

Rocky Springs sounds like the name of a small town in a 1950s or 1960s movie. In fact it is (or was) a small settlement a few miles East of the Mississippi river. In 1860 it had 2,616 residents, now it has none. So, who, or what, killed Rocky Springs?

First of all, the name is misleading. There is not a rock in sight and there are no springs; water was accessed by wells. The soil is a deep loss, resulting from the wind depositing fine soil particles over countless years. This is one of the reasons for the settlement being established. Originally, the newly cleared land was fertile and easy to work.

However, the main reason for the establishment of the settlement was that it was a day’s walk along old Indian trails north of the delightful town of Natchez, which is on the banks of the Mississippi. Settlers in the northern states would float wood and firs down the Mississippi and sell them in Natchez and walk the 1,000 miles or so back home.  And they would stay the first night in Rocky Springs.

Now the land and the settlement itself, except a still active church, have returned to woodland. The only other signs of habitation are the Post Office safe and a few stone wells standing forlornly in deeply scarred woods. So who, or what, killed Rocky Springs?Rocky Springs Post Office Safe

There are two suspects; steam boats and soil erosion.

Steam boats were introduced in the 1850s and offered an easier and safer way for settlers returning home. Bandits soon proliferated on the walking tracks and it became very hazardous to walk home with all that cash. So the overnight accommodation business dried up.

The perceived wisdom is that the settlement had grown to such a size it would have been self-sustaining, provided that arable cropping continued to flourish. However, the virgin arable land soon lost its initial fertility and things became tougher. On top of that, soil erosion became horrendous and there are still signs of the huge gullies that formed after a heavy rain.

That set me thinking as to whether, with today’s technology, arable cropping would have survived and even prospered at Rocky Springs. Obviously, fertilisers would have enabled crop yields to be optimised in a soil that would soon lose any fertility built up under woodland. Secondly, would minimum tillage or no-till farming have prevented soil erosion? I don’t know the answer to this but we did see some arable cropping in the area and it was clear that no-till was being practised to establish both cotton and maize.

What struck me was the low intensity of arable farming in the south eastern states of the United States. It may be that there is tremendous potential to increase production in these states should the world food supply levels become more critical. In some areas at least, no-till would be essential to sustainability and glyphosate would be the key. Hence this herbicide, much demonised by some groups, would have an essential part to play. With a fresh start in these areas, there would be every reason to think carefully as to how it would be deployed in order to prevent resistance.  The penalties of over-reliance are only too clear in other parts of the United States.

I suggest that those who wish to go back to more traditional methods of arable production visit Rocky Springs. There isn’t much to see but the lessons are clear.

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