NIAB - National Institute of Agricultural Botany

Orson's Oracle

Hope versus fear

Posted on 22/08/2014 by Jim Orson

I read recently, possibly in the Farmer’s Weekly, that a Scottish farmer said their Independence Referendum is a choice between hope and fear. Thinking about it, I suppose it was always going to be so. The ‘yes’ campaign is bound to be espousing their hopes for an independent Scotland and the ‘no’ campaign is bound to be expressing their fears. The art is to try to identify whether the hopes and fears expressed are realistic or unrealistic.

There are choices between hopes and fears to be made in arable agriculture, particularly at a time when market prices are less than the cost of production. As an aside, I am slightly amused that I have yet to hear from a farmer who has not sold a substantial proportion of this year’s cereal harvest a few months ago when market prices were considerably higher!

I am sorry to fall on familiar territory but many farmers’ approaches to black-grass control over the last few years have been based more on unrealistic hope than realistic fear. I gave talks a few years ago where the farmer audience seemed hostile to my concerns over future control. There is no doubt that it is easier to ‘sell’ hope rather than fear.

I remember one particular meeting where farmers appeared to be convinced that more competitive varieties were the answer to the impending crisis. I explained that if such varieties behaved consistently in reducing black-grass seed shed by 25-50% then the herbicide control required in order to stand still in black-grass plant numbers was only reduced from 97% to 95-94%. It was clear that they did not want to believe me.

However, the maths of black-grass control only shows the huge challenge for cultural control. By the way, varieties vary between years in their relative competiveness against black-grass; there is no consistency. Indeed, the lack of consistency of cultural measures is a major issue but it is clear that when you are in the mire with black-grass, increasing crop competitiveness is not sufficient alone to turn the tide. Perhaps the most consistent and effective cultural control measure is spring cropping but even then, in 2013, there was a huge black-grass emergence in some spring drilled crops.

There have been unrealistic fears expressed over the cultural control measures of ploughing and growing spring barley on heavy soils. The doubt expressed about ploughing is that it will destroy the soil structure built up over the years by non-inversion tillage to about 20cm depth. The evidence produced by NIAB TAG’s NAC STAR project, on medium clay in Suffolk, suggests that in crop yield terms this is not a concern.

The other fear is that it is impossible to establish consistently spring barley on heavy soils. As I said in my previous blog (Climate and rotation), this year was particularly challenging in this respect but the machinery now available is better able to establish great spring barley crops. I have to admit that spring cropping on heavy soils is always going to be more risky than early autumn drilling but the level of fear in some farmers’ eyes is perhaps too high.  

Many farmers have now given up realistic hope of continuing with early drilled continuous autumn cropping established after non-inversion tillage. Personally I am convinced that to get to a more stable situation there is a need on many infested farms to reduce dramatically background black-grass populations by taking radical cultural control options rather than hoping to manage moderate populations from year to year. The realistic fear, even with a huge expenditure, is that chemical and cultural control measures will not be consistent from year to year and the economic consequences of a moderate population not being controlled are very significantly higher than a low population not being controlled. In addition, herbicides give higher levels of control of black-grass heads in low populations when compared to moderate populations.

So whilst we have to give up realistic hopes, at least over the next few years, of being able to control black-grass in rotations that consist only of early autumn drilled crops, perhaps the fears associated with some cultural control measures are unrealistically pessimistic.     

Blackgrass

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Climate and rotation

Posted on 13/08/2014 by Jim Orson

My final pre-harvest prediction of wheat yields was superseded by the actual harvest! As expected, yields are exceptionally high in some areas. The reported variable yields must in part be explained by the variation in June rainfall, which was a result of localised storms rather than frontal rain. Solar radiation in June and July was well above average and temperatures were not too high until the very end of ripening.

It was on a recent and beautiful sunny Sunday morning that I noticed that my neighbour’s leylandii hedge appeared to be dying. The Cambridge Council tree officer was kind enough to visit and said it was due to the high number of aphids that had survived the exceptionally warm winter. Apparently, this is the worst year in living memory for such damage. So, my neighbour and I have sprayed thrice with a legal neonicitinoid, but there may be lasting damage to the hedge.

Is this a result of a warming climate? There are other clues in our garden. For instance, this is also the first year that I have had to spray my zonal pelargoniums (geraniums) against rust. From a personal point of view, after a shower my hair now dries three or four time more quickly than when I was a teenager, but my wife diplomatically points out that there could possibly be less of it.

The mild winter has had its impact on UK agriculture. The challenge from yellow rust in wheat has been exceptionally high. The only compensation is that there appears to be no resistance in yellow rust to the major groups of fungicide used on wheat. The mild winter and early drilling may also have contributed to the difficulty in controlling triazole-resistant septoria in wheat. All this has resulted in more flexible and expensive fungicide programmes, banging a further nail in the coffin of the old (T0), T1, T2 and T3 approach.

One problem with the exceptionally mild winter was that there was little or no frost tilth present on the heavy soils when the spring crops were sown. This problem was magnified by the fact that it was extremely wet in the early spring and, in many areas, when it eventually turned dry there was little further rain in the following two months to support crop establishment. In the ‘old days’ this could have been disastrous because the seedbed cultivations would have dried out the soil resulting in poor and slow crop germination. In fact, this is what happened in some cases this year when a combi-drill was used. However, where the crops were established into autumn cultivated land with a single-pass disc or with a disc direct drill the germination, establishment and initial growth was superb despite the very dry March and April.

This experience is great in order to convince those farmers who are knee deep in black-grass to consider adopting spring cereals in order to break its life cycle. Possibly one of the reasons for their reluctance is the memory of trying to establish a spring cereal crop in conditions similar to this year. The thing is that equipment has changed dramatically since they may last have tried to do it, and now we have better machines for the job. These make spring-sown cereals a much more resilient and sustainable cultural control option. I must admit that I am not a ‘tyre-kicker’ and this is perhaps the full extent of my knowledge on drills, but I think that I have made my point.

Talking of difficulties with drilling and crop establishment, we’ve just had a visit from a NZ farmer who reports the trauma they have recently been going through whilst trying to establish autumn-sown cereals and small-seeded crops.

They have had exceptionally wet and dull conditions for months. Lack of sun resulted in disappointing wheat yields and the rain meant a difficult and delayed harvest. In the main area on the Canterbury Plains, especially on heavy soils, there have been few small-seeded seed crops and winter wheat crops established in their autumn. Some crops that were sown have failed. The only realistic option for many farmers in this part of the world is now spring barley.  

It is their worst late summer and autumn for arable farming in living memory and confirms that we are not the only ones who suffer from prolonged periods of extreme weather.  Such events plus that of pesticide resistance and pesticide withdrawals mean that farming and the supply industries must adjust to a more flexible approach.  In the UK, sowing spring crops on heavy soil is now part of that desired flexibility. The old certainties seem to be disappearing.

NZ Canterbury Plain - autumn drilling 2014

June on the Canterbury Plains in New Zealand. This is a time of year when fields should be green with vegetable seed crops, grass seed crops or winter wheat. The grass margins provide a firm base for the passage of linear boom irrigation equipment along the field (when needed!!!).

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Black-grass, the year of the double whammy

Posted on 22/07/2014 by Jim Orson

Our garden and allotment are now in full production and currently we do not have to buy any vegetables. This weekend we ate our first tomatoes and the first aubergines are a few days away. We really enjoy gardening but over the years I have often considered whether producing our own vegetables is economically worthwhile. This is particularly so when my wife has to struggle with a dirty and misshapen parsnip when the local corner store (Waitrose) can provide washed and perfectly shaped roots!

It is with this in mind that I recently studied the price of vegetables in the local corner store whilst sipping my free coffee. After a while I came to the conclusion that it was worth growing the basics such as potatoes, lettuce, onions, shallots, leeks, parsnips, broad, French and runner beans, butternut squash and courgettes. However, things like tomatoes, aubergines, peppers and chillies are our loss leaders particularly when we have to take into account one of our daughters or a neighbour having to water the greenhouse when we are away. I even have to hand-pollinate the aubergines with a paint brush and yet you can buy a large and perfect example for around 70p.

This is a microcosm of world trade in food. Grow what you are best at and import the rest. UK heavy land farmers can grow wheat competitively because of high potential yields. However, to exploit this potential we have to apply a high level of inputs.

Perhaps I am biased but it was the introduction of herbicides such as isoproturon that set the foundation for exploiting this high yield potential. Not only did it allow us to grow more wheat on the land most suited to its production but also to use non-inversion tillage and to sow earlier. Early sowing has three advantages; it enables a longer drilling window (so spreading machinery costs), in many cases it results in a higher yield potential and it also helps to ensure that the operation is carried out in good soil conditions.

Black-grassIt cannot have escaped anyone’s notice that this foundation for exploiting our potential for wheat production is now being undermined by herbicide resistance in black-grass. The industry has no option but to take this on board. No longer do farmers believe that high herbicide use and a minimum of cultural measures will overcome the problems they are encountering. There is a realisation that two or even three years of spring cropping (plus herbicide use) may be required to get some populations under control.

Amongst all the gloom, it is worth bearing in mind that this year we may have suffered a bit of a double whammy with black-grass populations. The epically cold and wet summer of 2012 resulted in high levels of dormancy and a very significant proportion of the black-grass seed shed in that year would not have germinated until the autumn of 2013. The summer of 2013 was conducive to low dormancy which meant that a very high proportion of the black-grass seed shed last year would also germinate last autumn. This helps to explain the rather unbelievably high numbers of black-grass that emerged after early drilling last autumn.

We are not alone in having pesticide resistance challenging the most economic production methods developed when the pesticides were working effectively. I have mentioned before that in Ireland, which has the highest average wheat yields in the world, there is caution in sowing a very high proportion of wheat in the rotation because of the danger of fungicide-resistant septoria dramatically reducing yields. In Australia, the measures required to control herbicide resistant rye-grass (Lolium rigidum) have had an enormous impact on rotations. A visiting Australian consultant told me at the weekend that the attention to detail required has made them better farmers. I am sure the same will be true for black-grass control in the UK but try telling that to the bank manager.

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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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