NIAB - National Institute of Agricultural Botany

Orson's Oracle

High wheat yields; a rollercoaster?

Posted on 03/02/2017 by Jim Orson

In a recent blog I discussed the fact that the variation in physical yields between varieties in the winter wheat recommended list trials is the same in both high and low yielding situations. My logical conclusion is that variety choice, in terms of percentage output, is more influential on crop output in low yielding situations. I am sure that in the current economic climate of UK wheat production, an extra 0.25 t/ha due to variety choice will be more welcome by a farmer averaging 7 t/ha than by a farmer averaging 11 t/ha? Of course, this assumes it does not cost more to achieve that extra yield.

Comments have been received on this conclusion. It was argued that farms have both low yielding and high yielding crops and also that yields vary between years. However, I am sticking to my guns because there are fields and farms that consistently have yields well above and well below national averages. Also, there are regions in the UK where yields are fairly consistently above or below national average yields.

An example of a high yielding farm is Salle Farms, near Norwich. The graph below shows the progress in winter wheat yields over the last two decades. Yields are up by 2 t/ha whilst the average yields for England and the Defra Eastern Region have barely increased. You will have to attend the upcoming AAB/BCPC conference to hear how Poul Hovesen has achieved this enviable performance. 

Jim Orson blog -

What intrigues me is that the peaks and troughs in yields at Salle seem to be more exaggerated than those in the English and Eastern Region averages. Maybe this is inevitable because yields on individual farms will vary more from year to year than national or regional averages. However, I have done some crude statistics and the peaks and troughs at Salle are far higher. At the very least, the graph shows that high yielding farms are not immune to volatility in yields and are perhaps more prone, in absolute yield terms, to significant year to year variation.

Should this be the case, then it is perhaps straightforward to proffer an explanation. I have been attempting to predict wheat yields in early July blogs each year since 2012. It is a far easier task when there is no significant shortage of soil moisture. This means that one key weather variable can be dismissed. The real challenge is in years when it is dry in the spring and early summer. Has crop growth been largely unhindered or has the lack of moisture had a significant impact on final yield?

Unfortunately for yield forecasting, high yielding years tend to have dry springs and early summers. With less cloud there is more solar radiation to drive yield potential. Hence, achieving high yields is a tightrope act of getting generous supplies of solar radiation whilst ensuring there is sufficient moisture available to enable the plant to process it into yield. In such situations, soil moisture supplies are crucial and high yielding farms have crops with healthy roots growing in healthy and moisture retentive soils. This combination of healthy roots and healthy soils may explain the significant peaks at Salle and also the less significant yield increases in some years when the national and regional crops remain fairly average.

In low yielding years there tends to be more rain in the spring and early summer and as a result less radiation. For instance, the Junes of 2007, 2012 and 2016 were all wetter and cloudier than average. In such conditions, most or all crops have sufficient moisture and provided that they have a full canopy are able to exploit the lower amount of solar radiation. This results in an overall drop in yield and a coming together of yields on typically high yielding and low yielding farms i.e. adequate (but not too much) rainfall in the spring and early summer are a leveller of crop performance. It is worth pointing out that 2001 had a fairly dry May and June but yields on all farms were lower than average because of the inevitable damage done to the soil and roots in the appallingly wet autumn/early winter of 2000 and early spring of 2001. This was the stuff of nightmares.

To be more succinct, good crop and soil management ensures that yield potential is exploited to the utmost in years when it is high, but in years when low solar radiation significantly limits yield potential, there is not much that good crop and soil management can do to compensate. The disappointing aspect of this observation is that whilst good crop and soil management lead to higher yields they do not appear to reduce the variation in yields from year to year, they may even increase it.

To be even more succinct, the answer lies in the soil (and its management).

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The real organic revolution

Posted on 20/01/2017 by Jim Orson

In 1943 the then Ministry of Agriculture and Fisheries introduced an Approvals Scheme for proprietary insecticides and fungicides in certain chemical groups. This voluntary scheme was for efficacy only and the approved products had a logo on the label indicating that it did what was claimed.Manufacturers or their agents had to pay a non-returnable application fee of 3 guineas for each product. Another world!

The two scanned pages that appear later in this blog show the complete Approved Products list, first published in 1944. All pesticide groups were added over time. The voluntary Approval Scheme continued until 1985 and the annual list of Approved Products was published in what was known as the orange book. By the end of the scheme the orange book was the size of a longish novel. In 1985, the Food and Environmental Protection Act (FEPA) introduced comprehensive statutory controls of pesticides, including efficacy evaluation.

Amazingly, the efficacy based Approvals Scheme preceded any regulations relating to pesticide safety for human health and the environment. Eventually, The Agricultural (poisonous substances) Act 1952 was introduced to protect agricultural workers from the most toxic products by requiring that protective clothing be worn when using pesticides and restricting the hours permitted to work with them. In 1954 the Government established the Advisory Committee on Pesticides (ACP) as a principle source of advice on pesticide safety issues. A voluntary ‘Clearance’ scheme on pesticide safety, the Pesticides Safety Precautions Scheme (PSPS), ran from 1957 for agricultural products; non-agricultural products were included from the mid 1970s. This voluntary scheme was also subsumed into the first statutory controls under FEPA in 1985. It has to be stressed that whilst PSPS and the Approval Scheme were voluntary, every UK based manufacturer sold only ‘Cleared’ products whose uses were typically Approved a year or two after ‘clearance’. It was the advent of imported ‘Non-Cleared’ products that resulted in the introduction of statutory controls through FEPA.

It is interesting not only to look down the first list of approved products but also to look at the names of the companies selling them. Those as long in the tooth as I am will recognise many of the names but I think that Bayer and H.L Hutchinson are the only companies still trading. Bearing in mind that the year of the list is 1944, the inclusion of a German company is hard to understand. I assume that the then Bayer Products Ltd. was trading independently of its parent company! The other companies on the list have simply stopped trading or were subject to company mergers.

Looking down the list makes me grateful for the modern era of organic chemistry (also referred to as carbon-based or synthetic chemistry) which is the basis of not only more efficacious products but also safer products. Organic chemistry is perceived by some as unnatural but in the case of several products in the first approvals list, returning back to ‘natural products’ would have some serious consequences for human health and the environment.

Keep up to date with crop protection and crop production issues by attending the AAB/BCPC conference Crop Production in Southern Britain 2017, kindly supported by Adama. The conference is to be held on 15th and 16th February at the Peterborough Arena (on the showground). Click here for more details. 


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How to get high wheat yields with nitrogen

Posted on 07/01/2017 by Jim Orson

One of our daughters had a weird dream over Christmas. Apparently, I went missing for six months and was eventually found on a golf course. When asked why I had not returned home earlier I simply replied that I was having a bad round. Obviously, at least one of our daughters thinks that I have fixations. Golf is probably one and another is definitely looking at how data can provide guidance to farmers.

I have recently been looking at datasets of nitrogen trials on winter wheat. This is a risky exercise because of the variable nature of results and the way optimum doses are calculated. Imposing any assumption on the shape of the response can influence the results and maybe mask the true answer. However, using the conventional methods, which may not be correct for some individual trials, the datasets I have examined allow me to have a more informed deduction as to how to get high wheat yields with nitrogen. It seems that the way to get high nitrogen-fertilised yields is to get high yields in the absence of applied nitrogen. In general, the higher the unfertilised yields, the higher the fertilised yields. I think that most farmers either know or suspect this to be the case. Good crop and soil management and favourable weather conditions are the key, with nitrogen providing the icing on the cake.

In these databases, for every extra tonne of nitrogen-fertilised yield/ha there is a contribution of at least half a tonne from the yield without applied nitrogen. One very large database suggests that for every tonne of nitrogen-fertilised grain/ha, two thirds of a tonne comes from the yield without nitrogen. These observations have a surprisingly high level of statistical validity for nitrogen trials. The associations explain to me why the additional amount of nitrogen required for very high yields in field trials is less than would logically be expected.

I have to say that the contribution of yields without nitrogen to increasing fertilised yields vindicates the nitrogen recommendations for feed wheat, based on field trials, provided to NIAB TAG members over the last ten years or so. These recommendations ignore Soil Mineral Nitrogen (SMN) levels if below 100 kg N/ha (i.e. nitrogen indices 0-3 in the current version of RB209) and only suggest applying relatively small amounts of additional nitrogen to a realistic base dressing when field yields are expected to exceed 10-11 t/ha. This is in contrast to the current version of RB 209 where the recommended doses decrease significantly between nitrogen indices 0-3. The reason why SMN can normally be ignored at these levels of SMN is because potential yields tend to increase with more available soil nitrogen: therefore the crop can economically use it and the additional nitrogen applied over and above the reduced doses recommended in current RB 209 for nitrogen indices 2-3. This is a rather neat self-correcting system. It appears to explain why there is, on average, no real difference in the economic optimum nitrogen dose in field trials carried out in situations where SMN is anywhere below or around 100 kg N/ha.

The conclusion of this piece is to reinforce my usual plea that we should be more cognisant of what field trials are telling us, despite their associated frustrations and errors. Now that I have got that off my chest I must return to the golf course.

Best wishes for 2017 (and don’t overdo the nitrogen).

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2016 wheat yields – a post mortem

Posted on 17/12/2016 by Jim Orson

Back in July I forecast average wheat yields, with some areas having yields on the disappointing side of average whilst the far North perhaps having above average yields. Well, as they say on Strictly “the results are now in”. The Defra estimated yields are in the following slide. I have included national yields for England and Scotland as well as two English regions of interest.

                 Jim Orson NIAB TAG blog - wheat yields

Yields in all regions of England were around average suggesting that my concern over lack of June sunshine leading to slightly lower than average yields in some areas may have been slightly over-egged. This may be because I wrote the blog in the first few days of July and then the first half of July turned out to be relatively sunny. Also, my contention that the very North of England might experience better yields than average turned out to be slightly optimistic although some very acceptable yields were reported. Scotland did have a good year. The yields in Yorkshire and Humberside came back down to average after the outstanding yields of 2015. Yields in the eastern region were actually lower in 2015 than 2014 due to the dry early summer last year.

Perhaps I was over-influenced by the June sunshine data, as shown below. There are one or two comments worth making. Sunshine hours are not directly related to the amount of radiation that drives potential yields and the graphic is for sunshine hours in relation to the average and not absolute values.

It is now very clear to me that measuring total radiation is not an entirely accurate approach to measuring yield potential, even when water supply is not limited. Not all the spectrum of total radiation is used for photosynthesis. Photosynthetic active radiation would provide a more accurate estimate of yield potential than total radiation. Photosynthetically active radiation, often abbreviated to PAR, defines the spectral range (wave band) of solar radiation from 400 to 700 nanometres within which photosynthetic organisms are able to photosynthesise.

Jim Orson NIAB TAG blog - June 2016 sunshine duration

There is a limit to the amount of radiation that plants can process in a day. This is often around 60% of that which occurs on the very brightest of June days. It is far better to have radiation spread out evenly over a month than have the vast majority concentrated into a few days of the month. An outstanding feature of the record wheat year of 2015 was that nearly every day from March to mid-July had a few hours of sunshine and this resulted in a better exploitation of the energy received.

Compared with harvest 2015, with its mild and dry winter and spring, an exceptionally sunny April and a few hours sunshine nearly every day in the late spring and early summer, 2016 had less overall radiation during the spring and summer, a very wet winter and early spring and a cold April. When you take all this into account, the yields of 2016 held up well.

I wish you all a great Christmas and New Year.

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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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