NIAB - National Institute of Agricultural Botany

Orson's Oracle

Peak Wheat

Posted on 02/12/2016 by Jim Orson

The Soil Association was making a huge fuss over ‘Peak Oil’ around the new Millennium. Subsequently, new technology has resulted in the fears of an oil shortage evaporating. The reason for highlighting Peak Oil was that the Soil Association appeared to believe that conventional agriculture is more vulnerable to energy prices than organic agriculture. This may have been good PR at the time for the organic industry but the fact is that organic agriculture is possibly more vulnerable to energy shortages and price. Herbicides and fungicides produce huge yield benefits from relatively little energy use which may more than counteract the high amounts of energy that are needed for nitrogen fertiliser production.

Until recently the Soil Association was making ‘Peak Phosphate’ a feature in its campaigns and on its website. It was stated that we have only around another 30 years of phosphate in reserve. It is true that the mining companies have approximately 30 years of declared reserves in their accounts but the US Geological Survey estimates that there are at least 1,500 years of phosphate reserves to meet current demand. Peak Phosphate was to publicise the organic movement acting responsibly by recycling nutrients. Another PR exercise which is not borne out by the facts. Conventional farmers also recycle nutrients, possibly to the same extent, but are admittedly not so dependent on this source of plant nutrition when achieving significantly higher yields/ha.

Jim Orson - Peak Wheat - NIAB blogI think it is my turn to introduce a Peak, in this case Peak Wheat. Has the UK passed its Peak Wheat production? We produced 17.2 million tonnes in the 2008 harvest year; a combination of planting more than 2 million hectares of wheat and of what was then a record average yield/ha. In 2014 and again in 2015, we surpassed the record average yield/ha set in 2008 but the 5-10% lower area of the crop resulted in a total production of around 16.5 million tonnes.

The smaller area of wheat production in recent years can be attributed to a number of factors which now include herbicide resistance in black-grass. Effective and relatively cheap weed control makes it more likely that rotational and crop management restraints can be eased thus allowing farmers to maximise the area and potential of the most profitable crops. Take that away and there is a necessity to take the traditional rotational restraints more seriously. In this case, herbicide resistance in black-grass means less autumn-sown crops and also a higher proportion of later autumn-sown wheat. All this results in a smaller heap of wheat unless the yield potential of wheat increases very significantly.

Then there is also the issue of how agriculture will be supported in the future. It seems to me that there may be less overall support and perhaps a greater proportion of that support will be devoted to environmental enhancement. This may mean less crop production in parts of the country where yields are average or below, particularly where there is also an intractable black-grass problem. In these circumstances the temptation may be to restrict the area of crop production to the highest yielding parts of fields or farms and to increase the area devoted to environmental enhancement.

A realistic total cost of growing a hectare of wheat is around £950-£1,000/ha, which at current prices means that a yield of around 8 tonnes/ha is required to make a profit. Our 5 year rolling average yield is about 7.9 t/ha: food for thought. It is also worth pointing out that winter wheat and winter oilseed rape are the only two crops that many farmers can grow which will turn a profit without support from the Government.

All this sounds gloomy but there are scenarios that will mean we have not passed Peak Wheat. Plant breeding breakthroughs are now more likely with the accumulating knowledge of the genetic makeup of the crop and the new breeding techniques that are currently being used or being developed. There is also the possibility that wheat prices may reach a higher plateau as a result of an increasing world population and increasing climate uncertainty. Finally, an effective black-grass herbicide in wheat or herbicide-tolerant crops may be around the corner. Would I bet my shirt on these happening in the short to medium term? ……. perhaps not.

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Isoproturon – the great soil improver

Posted on 18/11/2016 by Jim Orson

We live in the Trumpington ward of Cambridge. Since the US election there has been a debate amongst some residents about the Trump in Trumpington. A local LibDem councillor has been very concerned and has changed his Twitter handle because it contained the dreaded word Trump.

Trumpington is expanding at an enormous rate and the land where the famous Plant Breeding Institute (PBI) once stood is now being gradually covered with houses. I looked at the name of some of the new streets. They invoke memories of varieties past; Proctor, Rialto, Bead, Consort, Piper, Avalon, Charger, Kestrel, Osprey and Hereward. Many of these had the handle Maris. This was because the PBI entrance was on Maris Lane. Incidentally, I came across Mrs Maris’ grave recently when helping to give the churchyard a bit of a spruce up.

The other variety that appears as a street name is Huntsman. Its introduction helped to start the surge towards greater wheat yields in the 1970s. I started in the National Agricultural Advisory Service (the predecessor of ADAS) in 1969 and one of my first jobs was to sow a winter wheat trial in South Essex. It was the first year that Maris Huntsman was in the NIAB Recommended List trials and my scores showed that it was visually very disappointing over the winter. However, the harvest demonstrated its true value.

There were many other significant introductions to the industry during the 1970s; for instance, chlorotoluron and isoproturon came on the market in 1971. In the early years, chlorotoluron was the more effective black-grass killer but it was more vulnerable to herbicide resistance and isoproturon came to the fore in the 1980s.

Sprayer  - NIAB imageIt is easy to overlook what these herbicides achieved. My personal experience was that the longer-term arable soils had terrible structure in the late 1960s and 1970s as a result of intensive late-autumn and spring-cropping. At the same time the Government commissioned the Strutt report ‘Modern Farming and the Soil ‘. This was published in 1970/71 and described the parlous state of our longer-term arable soils. Effective grass weed control not only resulted in a huge increase in autumn sowing, with its attendant advantages of plant cover and an effective root system during the winter, but also their sowing dates were brought forward to a time when typically soils were drier and less susceptible to damage. This all resulted in a huge improvement in soil structure and helped to set the scene for a near doubling of winter wheat yields between 1976 and 1984.

Bringing forward autumn sowing dates also meant a larger crop going into the winter with the advantages that it entails: more plant cover over-winter and a larger root system. Now that we are seeing a retreat from autumn cropping and a return to later autumn sowing dates, we have to remember these lessons from recent history. There is evidence that these lessons have been learnt because of the current enthusiasm for cover crops prior to spring crops.

I have been debating with colleagues as to whether a cover crop followed by a spring cereal is as beneficial as an early-sown winter crop. Typically the objective of a cover crop is to produce more green material in the autumn than is achieved with a winter cereal crop sown at optimum seed rates for grain yield. In addition, it has been suggested (but not, as far as I know, proven) that it may be advantageous for the soil biomass of fungi and bacteria that the cover crop is an entirely different type of plant from the following spring crop and also from other crops that appear in the rotation.

A major issue on the heavy clays is that cover crop management is not easy, particularly the transition between the cover crop and the sowing of the spring crop because there can be a delay in the soil surface layers drying out in spring. I am sure that the inventiveness of the industry will come up with some practical solutions. My experience in the early 1970s suggests that these solutions will be very beneficial in helping to retain the structure of heavy soils where black-grass control necessitates spring cropping. However, it would more straight-forward and profitable to be able to chemically control black-grass in early autumn-sown crops!

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Nitrogen recommendations – it's very complicated

Posted on 04/11/2016 by Jim Orson

I wrote a blog in April (Precision application of nitrogen) on why I thought that experiments and field experience over the past 10-20 years have not shown a significant benefit in the spatial application of nitrogen in winter wheat. The recent publication of the AHDB project ‘Automating nitrogen fertiliser for cereals (Auto-N)’ has strengthened the argument that this approach to nitrogen fertilisation has little or no economic advantage.

The authors of the report seem to accept that the simplistic models that are currently used to predict nitrogen requirement do not take into account the unpredictability of nitrogen uptake by the crop, in this case winter wheat. In many cases there are interactions between the components used to predict optimum nitrogen requirement. For instance the authors highlight a possible negative correlation between soil nitrogen supply (SNS) and fertiliser recovery. Where SNS is high there is sometimes a lower recovery of fertiliser nitrogen by the crop.


However, despite the failure to define an approach that will make the spatial application of nitrogen pay in winter wheat, the report is full of data. I love data, but there is far too much for me to absorb. There are, though, some standout pieces of information and interpretation by the authors.

Highlighted in the project summary is the statement that high SNS is associated with high yields. We are familiar with the term SNS; in current recommendation systems it is the sum of Soil Mineral Nitrogen (SMN) in the spring,plus the amount of nitrogen in the crop at that time, plus an estimate of usable net mineralisable nitrogen released by the soil. However, in the report it has a different meaning: it is the amount of nitrogen in the crop at harvest in the plots that did not receive nitrogen, hence it is Harvested SNS. The interesting observation that high Harvested SNS is associated with high yields is only useful if it is predictable. Unfortunately it may not be; in this project the relationship between SMN and Harvested SNS was tenuous.

Other data collected in this project suggest that there is not a strong association between grain yield and nitrogen requirement. This confirms previous field and experimental evidence that very high yields can be achieved with moderate levels of nitrogen. In this project, plot yields in excess of 13 t/ha were achieved with 240 kg N/ha in a field which had modest levels of SMN. Last year, in a NIAB TAG experiment in a field with typical levels of SMN, treatment yields in excess of 14 t/ha were achieved with 220 kg N/ha before additional nitrogen was required to enable even higher yields. However, please remember that spot yields in excess of 14 t/ha can occur in fields averaging 10-12 t/ha.

To quote the report ‘the lack of a strong relationship between yield and nitrogen requirement raises some important questions’. The most important question is how yield expectation can be incorporated into future nitrogen recommendation systems. My view for feed wheats is that nitrogen doses should not be increased until field yields above 10-12 t/ha are expected. For field yields above this level any increase in nitrogen recommendation should be modest.

Any new recommendation system cannot continue to adopt the principle that each kg of SMN is equivalent to a kg of SNS. Continued adherence to this principle explains why RB 209 has too large a change between soil nitrogen indices in recommended doses for feed wheat.

AHDB has funded two large projects that patently show that each kg of SMN changes SNS by only up to half a kg. Reviews of field experiments and the Auto N project also indicate the surprising lack of influence of SMN levels below about 100 kg/ha on the economic optimum dose of nitrogen for feed wheat.

All this is perhaps summed up by this statement in the report: ‘However, the large and somewhat unexplained variation in measured N requirements means that any prediction system will inevitably produce errors and improvement over the standard recommendation system (or even a standard figure of, say, 200 kg N/ha) is likely to be relatively modest’. I think that the 200 kg N/ha quoted was in the context that a kg of nitrogen was five times more expensive that a kg of wheat.

I suppose that the only comfort is that errors of up to 50 kg N/ha either side of the optimum dose has a relatively small effect on the margin over nitrogen costs. Please remember that the doses of nitrogen quoted in this report are relevant to feed wheats rather than milling wheats.

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Average wheat yields

Posted on 21/10/2016 by Jim Orson

Defra has recently published its preliminary estimate of this year’s UK cereals and oilseed rape harvest. It suggests that wheat averaged 7.9 t/ha and oilseed rape a lowly 3.1 t/ha. Defra, like everyone else, has suggested that the wheat yield was ‘average’. That got me thinking; how is the average yield calculated, particularly if there is a current trend upwards or downwards?

Hence, I have produced two graphs of the average yields of wheat, using information from the excellent online FAOSTAT3 database for the years 1996-2014 and Defra data for 2015 and 2016. The data used by the FAO is taken from Defra’s final yield surveys but at the moment it covers only individual years up to the 2014 harvest.

The first graph shows the five year rolling average yield for UK wheat; hence, the 2016 average yield includes the yields achieved from 2012 to 2016. As you can see, this graph rather deflates the view that we are witnessing a breakthrough in yields. Average five year rolling yields have been virtually the same over this century.

The second graph shows the four year rolling average and this implies a different scenario. After a long plateau in yields, they appear to be on the rise following a recent dip.

What explains the difference between the two graphs is the year 2012. Taking that out of the picture, the high yields achieved in 2014 and 2015 have raised the 2016 four year rolling average yield. It is tempting to say that we should ignore the poor yields in 2012 where exceptionally low summer solar radiation and summer waterlogging resulted in such poor yields. However, on the same basis, should we perhaps ignore the near perfect conditions, particularly up North, for wheat yields in 2015?

So, in my opinion, we have yet to see clear evidence that wheat yields are increasing despite some spectacular results in 2015. In addition, this year’s oilseed rape yields have dampened a recent trend towards higher yields.

There is more than one reason for the rather ‘average’ yields for this year’s winter wheat yields and the poor winter oilseed rape yields. However, one common feature shared by both crops is that much of the country had poor levels of solar radiation in late May and June. This may have been more significant in winter oilseed rape than in winter wheat. This is because grain fill in oilseed rape is determined almost entirely by current solar radiation whilst a significant proportion of grain fill in wheat is provided by reserves laid down before flowering.

The generally low radiation levels in June are probably the dominant explanation for the relatively high protein levels in wheat this year. Grain fill was restricted whilst moist soils meant that there was adequate nitrogen in the wheat plants. Another explanation may be that farmers were mistakenly encouraged by the high yields in 2015 to apply more nitrogen in 2016. There is no evidence of a link between economic optimum nitrogen levels and feed wheat yields unless yields are exceptionally high. NIAB TAG data suggests that extra nitrogen may be required for yields above 14 t/ha but please remember that such yields occur in parts of fields that have an overall yield of 11-12 t/ha.

Defra publishes its final yield estimates in December along with regional yields. I will then comment on my predictions of wheat yields made in a blog in July. It sounds as if I was not too far out but, of course, the majority of seasons produce average or near average yields.

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Variety choice more important with low yields

Posted on 07/10/2016 by Jim Orson

I recently looked at the results of this year’s and last year’s winter wheat recommended list variety trials on the AHDB website. I was struck by the small differences between the percent yield of varieties in the highest yielding trial, which averaged over 17 t/ha. This spurred me to look at the standard deviation of variety yields in each of the fungicide treated winter wheat recommended list trials in 2012 to 2016.

Standard deviation is simply a measure that is used to quantify the amount of variation or dispersion of a set of data values. The results of this study are expressed graphically in the figure below. This shows that there is no trend in the standard deviation of the yields of the individual varieties (t/ha) and the average yield of the trial. The outlier showing a very high standard deviation was a second cereal on a light soil: this may have suffered from take-all and the records show that it experienced high pressure from septoria.

Does this ‘interesting’ observation have any real practical significance? That is a matter of opinion but it suggests to me that variety choice is more critical for low yielding situations, particularly when margins are as tight as they are now.

Looking at the data in another way, when the yield results are expressed as percentages rather than t/ha, overall the spread of individual variety performances in each trial reduces as the mean yields of the control varieties increase. In the figure below, the 2012 data, the lowest yielding year of the five years, has been highlighted.

Septoria pressure was very high in the extremely wet summer of 2012. Interestingly, I cannot find any evidence to suggest that there was an association between the level of septoria infection and the standard deviation of the physical yields of the varieties in the individual trials harvested that year. This indicates that the reasons why there are just as large yield differences between varieties, expressed in t/ha, in low yielding trials as in high yielding trials is probably more complicated than a single factor. They are possibly associated with the overall stresses incurred in individual trials that affect some varieties more than others. The trials were stressed by summer waterlogging in 2012 but in other years lack of moisture was a feature. Hence, this type of analysis may not help to improve variety selection in differing scenarios but it does emphasise that variety performance is economically more important in lower yielding situations.

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