NIAB - National Institute of Agricultural Botany

Orson's Oracle

It’s not every year that…

Posted on 14/07/2014 by Jim Orson

Tour de France in Essex 2014It’s not every year that you can walk ten minutes down to the end of your street and see the Tour de France go by. It is really a spectacle. We were lucky enough to see all the first three stages as one of our daughters lives in a part of Yorkshire that’s very close to where the first two stages passed. I must admit there appeared to be more enthusiasm in Yorkshire during the build up for Le Tour, but the citizens of Cambridge did turn up in huge numbers to see the start of the third stage. We went down to the centre of Cambridge early on the morning of the start and I heard an announcer say that France was the host country of the Tour de France. I guess we all say something daft on occasions.

It’s also not every year that has good conditions for the control of perennial broad-leaved weeds with pre-harvest glyphosate, but they do come round far more regularly than the Tour de France visiting Cambridge. This year in many parts of the country we’ve had sufficient moisture to encourage the active weed growth that is so necessary for good control with glyphosate.

The pre-harvest recommendation, announced in 1981, played a critical role in the development of UK farming systems during the last couple of decades of the last century. Before then, we had to wait until the couch and other perennial weeds grew to a sufficient size after harvest. This delayed cultivations and in many cases there was never enough growth of perennial broad-leaved weeds for effective control. In some years an early frost removed the green growth of creeping thistle.

You have to remember that there were many more couch and perennial broad-leaved weed infestations around when glyphosate was introduced. It was really the pre-harvest recommendation that did for these weeds. I’m often asked whether herbicides have been so efficient that they have destroyed their own market by eradicating all their target weeds. The only example I can think of is that perennial weed populations have dramatically been reduced by glyphosate and are no longer a common occurrence.

Pre-harvest glyphosateThe main reasons for the application of pre-harvest glyphosate nowadays seem to be general weed control rather than perennial weed control and to ‘aid harvest’ of weed free crops. I do have problems with the latter because all the independent trials I have seen suggest that the application does not bring forward the wheat harvest but it can bring forward the spring barley harvest by a day or so.

The claim for glyphosate ‘evening-up’ the ripening of wheat can be precarious. Pre-harvest glyphosate application can start when the bulk moisture content of the grain is 30%. In a very variably ripening crop a significant proportion of the wheat may not be fully ripe and continuing to put on weight despite the average bulk grain moisture being 30%. Hence, the application of glyphosate may not only reduce the yield but also, glyphosate residues in the grain may be increased.

This is not a theoretical notion; there is trial data recording yield decreases in such situations. Hence, pre-harvest application should start only where the bulk grain moisture content in the latest part of the field is at or below 30% and at this moisture content, as I said earlier, application will not bring forward the wheat harvest.

I’m also not sure whether the pre-harvest application to a weed free crop will make harvesting any easier. All the trials I’ve seen suggest that such applications don’t reduce the moisture content of the straw by the time that the grain is sufficiently dry to harvest. I suppose that it may be an advantage regarding the moisture content of the straw a couple of weeks or so after application but trial data also suggests that treated straw can become wetter than untreated straw where the harvest is significantly delayed by rain. This is logical because the treated straw may be degrading more quickly and therefore is more likely to absorb moisture.

So whilst I recognise the huge contribution that glyphosate makes to modern cropping systems there is always a need to question whether each application will produce the desired results.

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2014 wheat yields

Posted on 07/07/2014 by Jim Orson

The end of June is around halfway through grain fill of winter wheat and for the last couple of years I have had a stab at predicting the yields of the coming harvest at this stage. In 2012, I predicted below average yields, based on well below average levels of solar radiation, not just during the first half of grain fill but also in May as well. What I did not take into account was the negative impact of waterlogging during May and/or June which was very significant, particularly in parts of the Midlands.

In 2013, I predicted fairly average yields because of average radiation levels during grain fill and over the previous month and also because of the dryish soil conditions in many parts of the country. I did however predict higher than average yields for timely sown wheat in parts of Lincolnshire and further North because this part of the country received more than average radiation levels and some parts had some useful rains at the right time.

I must admit that I have less data available than in previous years for an early prediction this year but where crops have been kept weed and disease free, the yield potential looks very good. Like the good years of 1984 and 2008, we generally had a dry April but had good rains in May. Sunshine levels and limited radiation data suggest that whilst May was a bit below average, the conditions for grain fill have been better than average. In addition, we have had warm but not really hot weather, particularly during flowering. If I wanted to be picky, I would have liked the nights during grain fill to have been a little cooler so that the crop respired less of the weight it put on during the day.

There are many magnificent looking crops around and the wetter than average May has enabled them to sustain high tiller counts. I suppose the only downside was the exceptional wet winter which would have shaved-off some yield potential. Trials in very large containers (lysimeters) suggest that summer waterlogging is far more damaging to yield than winter waterlogging but the latter can have some affect.

There is still some time to go before the crop has finished putting on weight this year but it is interesting that the very high temperatures we experienced in the second and third weeks of July last year did not appear to be very damaging to yield. Not that I am saying we are almost there; in 2008, the very wet harvest compromised yields although on average they were still the highest we have achieved.

Therefore there are very solid grounds for optimism. I hope that in three weeks time I will be able to confirm this with some more accurate data than that I have available at the moment. As I have said many times before, the fundamental driver for yield potential is solar radiation. It is now clear to me that I have previously underestimated the value of good levels of solar radiation before the start of grain fill.

Wherever possible it is important that solar radiation rather than sunlight hours is measured. This is because an hour of sunlight at dawn does not provide the same level of potential energy to the crop as an hour of sunlight when the sun is at its highest. To be even more precise, only the wavelengths of radiation that the plant uses in photosynthesis should be measured (Photosynthetically Active Radiation).

Hence, I will try to improve my data sources for a final prediction over the next two to three weeks during which I hope the weather remains conducive to good yields. Here’s hoping that the wheat price will improve too.

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They think it’s all over….

Posted on 28/06/2014 by Jim Orson

Until the World Cup it has been a good footballing year for me. As a lifetime supporter of Leicester City, I was over the moon this spring because an amazing unbeaten run culminated in their promotion to the Premiership as champions of the Championship. Not only that, but I watched with a mixture of fear and excitement as the mighty U’s (for the few who do not know – Cambridge United) climbed to the top of the FA Conference Premier League at Christmas and then hung on for second place. A trip to Wembley was necessary to see them grab promotion to the Football League. This was their second Wembley appearance of the season as a few weeks previously, one of my daughters and I also watched them win the FA Vase (the equivalent to the FA Cup for non-league clubs). The photo shows them on their victory parade through the city at the end of the season.

Cambridge United victory parade 2014

Cambridge United victory parade 2014 2








Then came the World Cup; so near and yet so far. Naturally I remember the 1966 World Cup final win over Germany although I did not watch it on TV. Believe it or not, I was playing cricket for the local farmers’ team. However, we did have a radio behind each set of stumps and really lived the drama. In many ways it was perhaps a better experience than watching it on TV.

This got me thinking about how competitive we were in the world wheat yield stakes in 1966. So I looked it up and with increasing excitement found that our average yield that year of 3.86 t/ha was higher than Germany (of course!), Ireland (the current country with the highest average yields), New Zealand and France. At the last moment I thought I should check some other likely candidates and I am afraid that Denmark spoilt the story, with an average yield of 4.27 t/ha. It is sobering that their current yields are being compromised by significant nitrogen restrictions.

There is much current excitement about ‘breaking the yield ceiling’. It’s a bit like the World Cup; we spend hour upon hour planning the strategy and tactics only for the weather to prove too strong an opposition. We get so close but it is either not wet enough in the summer (e.g. 2013) or too wet and dull in the summer (e.g. 2012) for us to claim victory. Sometimes we lose in extra time. 2008 was our record year for average yields and it could have been so much better had it not been for the extremely wet harvest. That year I heard over and over again from farmers who said that they were half-way through harvesting a field when the weather broke and when they recommenced a fortnight later, the yields in the remainder of the field were a tonne/ha less.  As one Essex farmer sagely told me recently, wheat has only to look good once and that is when it is feeding into the combine i.e. it is not over until it is over.

There are some amazingly good looking wheat crops at the moment. With the right combination of sunshine and rain there could possibly be some bumper yields around. The recipe for very high yields is well known, the crop needs to intercept high levels of solar radiation and not run short of moisture. High temperatures during grain fill, particularly around and just after flowering, will reduce the yield potential.

There is a need to maintain a green wheat canopy until the end of grain fill. This is not the same as saying that a green crop canopy should be maintained for as long as possible. There is evidence in scientific literature that clearly shows that the relationship which exists between maintaining a green canopy and yield has a time limit (measured in day degrees) which is around the time of the end of grain fill.  

Extending a significant green canopy beyond that time does not further increase yields. Additionally, it does not have to be a full canopy at the end of grain fill, field experiments carried out at the University of Reading just over ten years ago suggest that by around the end of grain fill the majority of the flag leaf can be senesced and maximum yields can be achieved. Whilst I accept that such a canopy at the end of grain fill could possibly be insufficient for a record yield, it is clear that the canopy needs to be kept green but perhaps the rider ‘for as long as possible’ may be the route to some unnecessary expenditure.

It is interesting to note that whilst barley can be very different to wheat a recent HGCA project report shows that light interception by the canopy of spring barley must only be protected for approximately the first 75% of grain fill in order to maximise yield; a period of three to five weeks from 50% ear emergence depending on the site and year.  After that period, yield is insensitive to major reductions in light interception (e.g. caused by leaf diseases) probably because grain filling can be completed using dry matter from storage reserves.

So please remember, as always, do not get carried away with dogma but look at the results of field experiments and do not try to maintain the green canopy at all costs. Green is not necessarily the new gold.

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It’s a small world

Posted on 17/06/2014 by Jim Orson

The Cereals Event is held at a time of year when farmers look back over the season and hone plans for the coming season. This year, the change in the EU support arrangements and falling cereal prices prNIAB TAG at the Cereals Event 2014ovide much food for thought. Costs of wheat production have increased significantly over recent seasons and some farmers tell me that they now need £140-150 per tonne to break-even.

One of the reasons for the increase in costs of wheat production is pesticide resistance. Black-grass control is now very expensive with herbicide programmes often costing in excess of £140/ha in addition to the costs or income forgone that are a consequence of cultural measures. Septoria resistance has resulted in fungicide control programmes costing in excess of £100/ha. These two issues, along with the control of yellow rust, dominate many technical discussions.

I met the chief executive of a major Australian farmers’ research group at Cereals and he told me that they share the same technical challenges in wheat; herbicide resistance in grass weeds and rust and septoria control. It is indeed a small world. The last item may surprise you but the members of his group farm on the relatively wet coastal strip of Victoria. New Zealander visitors were telling me that septoria, typically less important than the rusts, has been a major problem for the last two wet seasons and that they now have, almost out of the blue, high levels of fungicide resistance.

It is interesting to read and hear that many believe that black-grass resistance is a failure of research and knowledge transfer. I agree that the issue has historically and frustratingly been under-researched. It has been obvious to weed scientists for the last two to three decades that it has always been a key issue and that the effective herbicide control required in order to support the rotations and businesses of many farmers would eventually be difficult or impossible to achieve. However, research funders could not be convinced. Perhaps, like many farmers, they believed that a new herbicide would appear and save the day.

However, we are where we are. The accusation that black-grass resistance is a failure of knowledge transfer is a little unfair. My weed research colleagues have in talks, scientific papers, press articles and leaflets, been banging on about the dangers. However, in most cases, farmers have chosen not to listen. I can understand this because we could not predict precisely the rate of development of resistance and asking farmers to forego income during hard times in the light of such uncertainty is, to say the least, challenging.

The case of Atlantis (iodosulfuron and mesosulfuron) provides a typical example of what has happened. It was introduced during the 2004 cropping season. By that time Lexus (flupyrsulfuron) and the ‘fops’ and ‘dims’ were fading fast. It was clear to weed scientists, even before it was commercially released, that resistance to it would develop quickly and warnings and label statements were issued. However, these were lean times for wheat and perhaps it is understandable that farmers over-relied on it to ensure that they could minimise the costs of production.

At Cereals there was also a strong interest in increasing yields bearing in mind the rising costs of wheat production. I have been lucky enough to have been invited to many parts of the world to observe and to speak on the subject. In particular, there tended to be a belief in many countries (with the exception of New Zealand!) that if they use inputs in the same way as we have done then they will automatically increase yields. I am afraid that typically my response to their hopes has been rather brutal; ‘it is the weather what does it’.

All we can do is to ensure that input and crop management enables the crop to make maximum use of solar energy and rainfall. In addition, in some climates cruelly cold or hot conditions can severely limit yields. It is rather naïve to believe still that there is a magic formula of input management which will dramatically increase UK wheat yields. On the other hand, we should never cease to look for marginal increases and to hope that our increasing knowledge of the genetics of wheat will lead eventually to a breakthrough.

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Losing flexibility

Posted on 06/06/2014 by Jim Orson

The level of risk management in arable cropping in many parts of Australia is awe-inspiring. Choosing the correct crop to grow and the level of inputs that will be required in relation to current (and future) weather conditions is critical. There are severe penalties for getting it wrong. Applying nitrogen in a dry year will reduce yields whilst there are enormous benefits from its use in a ‘wet’ year. Our decision-making over the last few decades has been by comparison straight-forward as witnessed by our relatively stable year-to-year yields.NIAB TAG Blackgrass Research Centre

However, things are changing for many UK farmers and the catalyst is black-grass resistance. No longer can herbicides be used to negate the risks involved with a totally autumn-sown rotation. This year many September sowings of wheat are severely infested with black-grass despite the huge use of herbicides. As every farmer knows, delaying sowings significantly increases the risks to crop establishment and yields.  

I gave a paper to the 1995 BCPC Brighton Conference entitled ‘crop technology; a flexible friend for the farmer and the environment’. In it I argued that the challenges of future food production whilst still protecting the environment would be best served by having technology that would give us the flexibility to manage crop production effectively. I did mention the possibility of pesticide resistance reducing this flexibility but the paper was written before the birth of another threat namely the EU Drinking Water Directive. This is putting the growing of oilseed rape at risk because the key herbicides can move to water in quantities that exceed the 0.1 parts per billion specified in the Directive.

So the question must be how do we react to the current situation? We discussed this when my colleagues in TAG Consultants visited the NIAB TAG Black-grass Research Centre last week. The bulk of the time was spent on the current difficulties in controlling black-grass and its impact on farming systems. All the alternative strategies put forward would result in a lower bottom line.NIAB TAG's John Cussans at the Blackgrass Research Centre Open Day

There are a few different approaches that may be taken but all of them must take into account the need to reduce background black-grass numbers. Lower background numbers would ensure greater flexibility because one would be further away from the cliff-edge of disaster.

Everyone is aware of the relative benefits of the different cultural control measures and the days are gone when many considered a mere tinkering with crop management was the solution. A major problem is that the full economic impact of the different approaches is almost impossible to predict accurately. There are not many heavy land farmers who have had a disaster from growing spring barley over the last few years, despite their own sometimes severe misgivings before they re-adopted the crop in order to reduce black-grass numbers. However, they may have a bad year or two in the future. On the other hand, there are many farmers who have regretted adopting later autumn sowing. One possible response to this is to choose varieties of wheat and barley that can be either late-autumn or spring sown.

A variation of this approach, straight out of the Australian ‘rule-book’, is to store home-grown undressed but tested seed of autumn and spring crops and/or varieties and to take advantage of any weather window that presents itself. Perhaps it is not necessary to look to the other side of the world for an example of this option. In parts of France farmers will grow sunflowers when the previous autumn has been too dry to establish oilseed rape.

An attractive option for many is to set out a rotation that contains sufficient spring sown crops in order that when winter wheat is grown it can be sown sufficiently early to optimise yields whilst reducing the risk of wet weather delaying or affecting the quality of establishment. The issue of winter oilseed rape is perhaps another debate; it is not easy to design an effective weed control programme that does not risk pesticide movement to water at a level that exceeds that specified by the Drinking Water Directive. Water Companies can generally deal with small exceedances but not the major peaks of concentrations that can occur.

This is the time of year to look at the level of black-grass infestations and to mull over the future. One thing is certain, there are no immediate prospects of miracle herbicides and so things will not get any easier.

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