NIAB - National Institute of Agricultural Botany

Orson's Oracle

Mind the gap

Posted on 02/07/2018 by Jim Orson

We have just returned from holiday and as the flight was on its descent into Stansted I witnessed a true cost of the failure to control black-grass effectively with herbicides. The spring barleys on the Essex clays did not look well. This is not surprising after a wet spring followed by the recent run of hot and dry weather. It is the kind of weather that many heavy land farmers have been dreading, but so far have avoided, having recently returned to spring drilled crops in order to break the black-grass growth cycle.

So it is clear: the inability to control pests, whether they are weeds or diseases or insects with crop protection products, can cost the farmer dearly and diminish food supplies. Despite this clear example, I read shortly after our return home that UN ‘experts’ have denounced statements that crop protection products are necessary to feed the world. The UN Human Rights Council has proclaimed that the idea that they are essential to feed a fast-growing global population is a myth. This is the same UN Human Rights Council that announced a few years back that Julian Assange’s time in the Ecuadorian Embassy in London amounted to “arbitrary detention”. This is on a par with the UN World Health Organization’s wish to appoint Robert Mugabe as a goodwill ambassador. It seems that UN committees are increasingly in the thrall of pressure groups.

The UN report on the “pesticide myth” was written by so-called food and pollution experts. However, they seem to have a funny view of the world. When discussing the very real issue of safe crop protection product use in countries which have undeveloped registration systems, they actually concluded that “the responsibility for protecting users and others throughout the pesticide life cycle and throughout the retail chain lies with the pesticide manufacturer”. This is comparable to saying that motor manufacturers have the sole responsibility for road safety in those countries with poorly developed traffic laws. Everyone can do better in increasing safe crop protection product use in some countries and this includes the UN. Luckily, some of the countries specifically mentioned in the report have now adopted GM Bt maize, soya or cotton which has resulted in a large reduction in the less than discriminate use of sprayed insecticides.

The report also praises the EU approach based on the so-called precautionary principle and criticises the USA for not adopting the same approach. I get the impression that many countries see that the role of the UN is to castigate western democracies, particularly the USA. That is by-the-by. The report says that US spray operators are insufficiently protected by regulations but does not acknowledge that surveys in the USA conclude that their spray operators are healthier than the average population. But… why let facts get in the way of a good dig at the USA!

So where has the more precautionary approach got us in Europe? It nearly got glyphosate unnecessarily banned despite huge health surveys in the US showing that the occurrence of the cancer it is accused of causing is no higher amongst farmers and spray operators. Neonic seed dressings are banned. Chlorothalonil (e.g. Bravo) is currently under the cosh despite being around for 50 years with no concerns, as far as I know, over its responsible use. Not only is it a key part of UK spray programmes for the control of septoria in wheat but it also helps to manage resistance of this disease in other fungicide groups. Chlorothalonil is also absolutely essential for the control of ramularia in barley. Hence, the loss of this active substance would have a significant effect on barley yields and productivity in the UK, at least in the short to medium term.

Perhaps we have reached the tipping point. There have been large numbers of crop protection products withdrawn over the last few years but, on the whole, the industry has got by and maintained productivity. This may have given the impression to some that crop protection products are not necessary. Now, however, the loss of the neonic seed dressings and the possible loss of chlorothalonil will hurt everyone unless we can agree a way forward. Losses such as these will leave a gap in sustainable crop production until researchers and plant breeders can provide alternative control strategies. We really need as a society to agree on ways of ‘minding the gaps’. Sadly, this wish is perhaps way too naïve in today’s fragmented climate of rule by pressure groups.

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Trust but verify

Posted on 19/01/2018 by Jim Orson

The heading for this blog is a quote from President Reagan made during the nuclear disarmament talks with the then USSR. It is something that should always be borne in mind when reading articles or listening to talks, even those by industry experts. There may be an ulterior motive in their slant on ‘the truth’ or they may not be thinking holistically.

I know that you want some examples. Let us start with The Soil Association and their campaign for healthier soils. They have fallen into the same trap as Michael Gove in quoting the loss of organic matter on the fen peats as typical. It is clear that either they have not seriously looked at the scientific literature or, having done so, have ignored it. This is because that over the last few decades soil organic matter may have actually increased on the very same long-term arable soils over which they express particular concern. The map below demonstrates this increase. The colour green indicates increasing soil organic matter between1978 and various time periods up to 2003 and the traditional arable areas are almost solidly green. The yellow colour shows static or slightly falling levels of organic matter and the red colouration represents a more significant fall in organic matter. You need to read the paper* to understand fully the basis on which this map is compiled. The fen peats of north Cambridgeshire are coloured red but their extent indicates how representative they are of the main areas of arable production in England and Wales. Interestingly, some of the areas losing organic matter most rapidly in both England and Wales are not farmed. The authors of the paper attribute this to climate change.


Why has organic matter most probably increased in long-term arable soils since 1978? There are two possible explanations. One is that straw burning generally stopped in the late 1980s and the other is that, because of the application of new technology and scientific understanding, we have been harvesting heavier crops since the mid-1980s. Heavier crops mean the return of more crop residues to the soil. In the long-term straw incorporation experiment at Morley, now funded by The Morley Agricultural Foundation, there has been a significant increase in soil organic matter since 1983 just from incorporating rather than removing straw. Mind you the soil organic matter is still between 1.7-1.8% where the straw has been incorporated but in some measurements, particularly soil aggregate stability, the benefit has been dramatic when compared to where the straw has been removed. It seems that the regular introduction of crop residues and a little bit of extra organic matter can go a long way.

I can hear you saying that The Soil Association is perhaps not an unbiased source of information. Their ‘peak oil’ and ‘peak phosphate’ campaigns, in which they predicted the fall of conventional systems, now seem an amusing aside. Also they are not thinking holistically about the wider environment because the extra manure use they promulgate has got to come from somewhere. I assume largely from extra cattle and sheep. This comes at a time when society is switching off eating meat and when there is a realisation of the profound effect of cattle and sheep on raising greenhouse gas production throughout the world.

Hence, I have another example. It is one that has been a ‘bit of a thing’ for me over the last few years. This is nitrogen advice for winter wheat. New ‘national advice’ has been all over the place for the last ten years or so. In my opinion this is because the advice has not been truly based on the evidence from field trials. Instead, the advice has been based on simplistic models that have been used to try to explain the results of field trials but when applied have not reliably reflected the nitrogen requirements of wheat, particularly at soil nitrogen indices of 2 and above. To some extent this has been overcome in the latest edition of RB 209 by introducing a yield correction.

However the yield correction is also a matter for debate. It was approximately 33 - 38 kg of applied N per extra tonne of wheat/ha in the AHDB Guidelines published in 2009 and then fell dramatically to an extra 20 kg/tonne in the new RB 209. This is still too high according to trials data.

Trying to make any sense of collated nitrogen trials can be soul destroying because of the lack of consistency, but there are exceptions. It has long been known that there is a robust relationship between yield at the optimum nitrogen dose and yield of the untreated control (also see my blog posted 7 January 2017). When a huge database of trials is analysed, including over seventy NIAB TAG trials from close to 60 locations, it shows that the optimum nitrogen dose increases yields by 3 t/ha when the treated plot yields are around 8 t/ha but by 5 t/ha when the treated plot yields are 15 t/ha. This means that the additional yield from nitrogen only increases by 2 t/ha when the optimum plot yield increases from 8 t/ha to 15 t/ha. This provides some verification of the NIAB TAG estimate that around 10 kg of applied N/ha is required for each extra tonne of plot yield above 8 t/ha. However, I have to point out that the differences between the NIAB TAG nitrogen recommendations for winter wheat and those in the new RB 209 are now far less than previously because of the other factors included in the calculations.

What really concerns me now is that some research organisations are gathering ‘facts’ via farmer forums on the internet. It has to be recognised that such ‘facts’ are a result of an inevitably biased survey and as such, the results should be treated as ‘interesting’ rather than true facts.

I have banged on for years in my blogs about seeking reliable practical guidelines from the correct interpretation of good scientific data. The message that should ring in our ears whenever we read or hear advice is “trust but verify”.


* If you have issues reading the paper, copy and paste the following link into your web broswer:

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Who would try to predict wheat yields?

Posted on 05/01/2018 by Jim Orson

Christmas is over and the days are slowly getting longer. This year I have decided to try to sow earlier some of my vegetable and flower seeds indoors, provided that I can get some supplementary lighting to stop them becoming ‘leggy’. This has meant doing a bit of research on LED plant growth lights. In the past they have promised great savings in energy costs but their prices has been prohibitive. It now appears that I can buy one for under a tenner.

The problem is that the choice is huge with differences in the balance of the blue and red light emitted. As a rule of thumb, the red part of the light spectrum is good for encouraging growth and flowering and the blue part is good for producing sturdy plants. Interestingly some emit a balance of light that is claimed to be equivalent to sunlight received at 10.00 a.m. (I assume GMT). This claim interested me because a couple of years ago I said in a blog on the reasons for high yields in 2015 that research suggests that morning sunshine is used more efficiently by wheat than sunlight later in the day. I have been digging around in the literature but have been unable to find any research findings on the implications on wheat of the spectrum of the light produced by morning sunlight.

Whilst searching the scientific literature, I discovered that the photosynthetic efficiency of wheat is influenced by the co‚Äźordination between supply (photosynthesis) and demand (sink size; during grain fill this is mainly the number of grains and their rate of growth). In general, photosynthetic rate declines when sinks are reduced but increases when sinks are increased (i.e. demand increases) (full details). Hence, high yielding crops use solar radiation more efficiently and this contributes to a more efficient use of nitrogen. In addition, the efficiency of use of solar radiation also partly depends on its daily distribution. It is better to have six hours sunshine every day rather than 12 hours sunshine every other day (full details).

Such variations in the exploitation of solar radiation by wheat help to explain why predicting yield is a fool’s exercise. Throw in the fact that other factors, such as soil moisture supply, can significantly influence yields only compounds the madness. Simple and fixed conversion rates of solar radiation to crop growth and yield can lead to significant errors in prediction. For example, using these simple and fixed conversion rates suggests that the South West should have the highest wheat yields but in fact Defra Statistics show that it is one of the lowest yielding areas in the UK.

Jim orson blog 211

Returning to my madness…. I have been attempting to predict yields in a July blog for the past few years. How did I get on this year? I concluded in a mid-July blog (uploaded on 14 July 2017) that ‘I think that in many parts of the country the wheat yields will do well to be above average. Second wheats seem to have particularly suffered from the lack of rainfall. However, yields in Lincolnshire and further North may be more pleasing’. Hence you can imagine my surprise when in early October Defra estimated that the UK yield was well above average at 8.5 tonnes/hectare. However, its final estimate published on 21 December is 8.3 tonnes/ha both for England and the UK. This is just above the 2013-2017 average of 8.2 tonnes/ha but well above the 2012-2017 average of 8.0 tonnes/ha. As you know 2012 was a low yielding year and including it lowers the average. This demonstrates how news stories can be manipulated by the choice of the comparators.

Therefore, I slightly under-estimated the yields in areas where there was a significant early spring drought. Dry springs are generally good for yields, partly because they are typically associated with above average solar radiation. This year the drought was severe enough and long enough for me to be concerned about its negative effects on average yields. However, wheat yields did suffer on light soils in some areas. My other concern was the warm spring and early summer that accelerated growth and development. This meant that there were fewer days than average for the crop to intercept solar radiation but I hoped that the above average levels of solar radiation during this time period would largely balance this out. It seems it did. Finally, there was concern about the blistering temperatures over a couple of days in late June but it seems that this was sufficiently far enough after flowering to have little effect.

In terms of regions, perhaps I was correct in predicting well above average yields for the North East and Yorkshire and The Humber.

One final observation. The graph below from Defra statistics indicates that after a 20-year plateau the five year moving average wheat yield is now rising. However, a repeat in 2018 of the conditions endured in 2012 may wreck this optimism. Let us hope for a good 2018 harvest.

Jim orson blog 211

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Changing behaviour of black-grass

Posted on 15/12/2017 by Jim Orson

I have regularly been asked whether black-grass has changed its field characteristics over the last 30-40 years. I have always given the same answer, an authorative “I dunno”. However, some recently published papers have suggested that the development of herbicide resistance may have had an impact on, for example, seedling emergence.

Resistance occurs by herbicides selecting plants with a mutant gene or genes that enable it to survive their application. Put simply, the predominant members of a population die as a result of herbicide application but a few individuals that have the mutant gene(s) will survive. Experience suggests that in black-grass such plants initially represented an incredibly small proportion of the population, perhaps one in 10-20 million.

Classically, resistant plants are less “fit” to survive, unless the herbicides to which they are resistant are used. This “fitness cost” may express itself in many ways, such as the ability to germinate and/or emerge or the size of the mature plant. This is perfectly logical because these resistant plants would not represent merely a tiny minority of the original population if they were as “fit” as the herbicide susceptible plants. Their only “fitness” benefit is likely to be the ability to survive the application of one or more herbicides.

A recent paper in Weed Science written by researchers in Denmark shows that the seeds from the non-target site resistant plants in a subpopulation of black-grass are less likely to emerge than those from the susceptible plants. The cooler the conditions and the deeper the depth of burial, the greater the reduction in emergence. This is a classical fitness penalty; the more hostile the conditions the greater the impact on some aspects of the life cycle of the plant.

Hence, this research indicates that the later the drilling in the autumn and the deeper the cultivations may have an increasingly negative impact on the emergence of seeds shed from the resistant plants when compared to seeds from the susceptible plants in the same population. This in turn may mean that such cultural control measures will now be more effective in reducing populations rather than when the original trials were done 30-40 years ago. It also suggests that early drilling and shallow tillage is likely to increase the proportion of non-target site resistant individuals in a population; this is provided that there are still viable seeds from susceptible plants remaining in the soil!

A few caveats before I get carried away. The subpopulation in this research was grown from seed harvested in one field. As we know, non-target site resistance is a variable feast and so these results may not represent all sites where this form of resistance occurs. On the other hand, there is typically a fitness cost to resistance. However, this is not always clear. A few years ago the implications of two mutations that confer target site resistance to the ‘fops’ and ‘dims’ in black-grass were studied. One mutation conferred increased dormancy, seedling vigour and seedling tolerance to environmental stresses whilst the impact of the other mutation was largely the opposite.

It is not all good news on the fitness costs of resistance. The same Danish group (Frontiers in Plant Science, November 2017) found that within the same subpopulation, the non-target site resistant plants had the same sized mature plants, the same number of tillers/plant and the same number of seed shed/plant as the susceptible plants. This suggests that if only herbicides to which there was no resistance were used, it would take decades or longer before susceptible plants would eventually become very dominant members of this subpopulation. So, do not hold your breath!

It seems that there must have been changes in the black-grass life cycle over the last 30-40 years due, if nothing else, to the development of resistance. The problem is that non-target resistance can involve a few mutated genes and target site resistance more than one mutated genes. Perhaps a simple pot experiment will indicate the likely extent of the changes. It is complicated but I can now say “I dunno” with even more authority.

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Sustaining conflicting ideas

Posted on 01/12/2017 by Jim Orson

Whenever I walk to Cambridge Railway Station I pass new buildings that are divided into ‘sustainable’ student flats. Each time I see that slogan I think “what makes them sustainable?”. They look like all other new build flats, which are no doubt well insulated. I also suppose they may have a few solar panels on their flat roofs. But sustainable no!

Sustainable is the in-word when discussing agricultural systems. It has been a ‘must’ for research applications for the last 25 years or so. However, it remains undefined and somewhat of a mystery to many. A bit like the student flats.

I recently attended a discussion on sustainable agricultural production at the Cambridge Department of Plant Sciences. For one speaker the answer was easy – ban cattle and sheep. She said that dairy cattle alone are responsible for 10% of the world’s greenhouse gas production. There is no doubt that agriculture is a major source of greenhouse gas production; I have not been able to verify that particular figure but it could be in the right ball-park.

Getting rid of cattle and sheep will also reduce the need for growing arable crops to feed them, further reducing the footprint of agriculture. I did ask the question what would happen to the upland farms if sheep production were banned. They not only provide an income and an infrastructure but also many tourists appreciate the landscape of fields being grazed by sheep. She was unrepentant and added that farming the uplands is responsible for flooding in many parts of the country.

Defra secretary Michael Gove is now talking about the loss of agricultural soils. He made the claim that Britain has lost 84% of fertile topsoil since 1850 and erosion continues in some areas at between 1cm and 3cm a year. I have been working in agriculture all my life and I do not recognise those figures. Hence, I read what I am pretty sure is the source document. It seems that the quoted losses are just for the peat fens and not all agricultural soils. Again, all agricultural production is implicated from a quote out of context. I am not sure if Michael Gove would recognise a fen peat if it hit him in the face but his advisers should know better. It should also be noted that in the 1960s and 1970s there was active state-funded research trying to find approaches to minimise carbon losses from the fen peats but, according to my knowledge, no research has since been done. There is one positive measure that could be adopted to prevent the loss of food production from organic peat soils and that is to prevent the construction of even more solar farms on this valuable resource.

Farmers do recognise there is a soil health issue and have moved much more positively than any policy maker. They are anxious to improve soil conditions and many use as much organic material as they can get. However, according to a House of Lords committee, there are apparently still some potential organic sources not being used. The recent widespread adoption of cover crops on the lighter and medium soils must be reducing soil erosion although their longer term benefits remain a subject of debate.

Large increases in soil organic matter remain an impossible task however desirable the objective. The necessary large scale use of organic manures is not possible because of limited supplies. The only other option is to sow long-term grass leys. Defra became keen on this idea a few years ago but then looked at the experimental data. For instance, in the often quoted ley fertility experiments carried out on the MAFF Experimental Husbandry Farms in the 1950s and 1960s, the lift in organic matter from a 9 year grass ley was almost completely lost in the following three years of arable cropping.

So the path to ‘sustainability’ is strewn with conflicts. Should we convert three quarters of our arable land to leys for a temporary small increase in soil organic matter? Should an increased population of cattle and sheep be allowed to graze on these leys because of the inevitable rise in greenhouse gas production? Will the banning of sheep and cattle result in a significant decrease in the availability of organic manures to improve arable land? Would it be asking too much to ask for some clear holistic thinking on the issue of sustainability based on what is possible through best practice rather than listening to, often unrealistic, solutions to individual issues?

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