NIAB - National Institute of Agricultural Botany

Orson's Oracle

Why is life like a Dulux colour chart in monochrome?

Posted on 16/08/2017 by Andrew Watson

I am a simple man. I like things to be black and white. Day follows night, e=mc2 and Game of Thrones is on at 9pm on a Monday. A book titled 50 Shades of Grey sounds like a nightmare read to me.

Take Brexit. A black and white decision was made, like it or not, but we appear to be entering a decade of greyness. Whether hard or soft, I think it will definitely be a lemon Brexit - slightly firm on the outside, soft in the middle, leaves a sour taste in mouth and why-o-why would you to chew on it in the first place?

Agricultural regulations, which I’ve been involved with for 25 years, are the ultimate grey. The ‘Ministry’ (which I’m always reminded of when I see Gringotts Bank in Harry Potter), put out definitive black and white rules on a subject and this is what the farmer has to do.

But it’s not black and white. It’s like producing a Dulux colour chart in monochrome; endless shades of grey as the rules are interpreted at a practical level, by the experts, on farm.

Look at the Nitrate Vulnerable Zones (NVZ) rules which were so vague that the farm inspectors at that time, The Environment Agency, would publish periodic semi-practical interpretations to make the rules less grey. Like it or not, at least it provided more clarity - more black and whiteness. Then independent farm inspectors came along and interpreted the rules further, and often completely differently, on an individual farm. Back to grey again.

Pesticide rules are so “grey” that it can be difficult for a farmer or advisor to interpret them correctly. Which of the numerous buffer zones applies and where does the buffer start? What water volume or spray nozzle can I use? What are the definitive legal requirements for using this pesticide product?

As some of you know, I’ve spent over a year developing the definitive black and white database of pesticide products. ActivSmart, a NIAB Digital service launched at this year’s Cereals Event, puts all the grey pesticide rules and product data into one place in sharp, defined colour. It allows users to easily compare the defined attributes of similar pesticide products; with up to 26 black and white facts on each of the 2,300 plus approved products on the database. It provides clarity; from active ingredient to maximum total dose, from arthropod buffer zone requirements to a document library. ActivSmart is the perfect project for me as I get to replace shades of grey with black and white.

However, despite ActivSmart (with all modesty) being by far the most comprehensive, up-to-date but still simple, pesticide comparison tool, there is still a nagging greyness for a small percentage of the data.

Let me give you an example. In 2017, a new buffer was very quietly introduced by the UK Chemicals Regulation Division (CRD). This 5 or 10 m ‘non-target plant’ buffer around the outside of the field currently only affects five of the 41 products containing the active ingredient clomazone currently approved in the UK (yet more unnecessary greyness). However, CRD has published two authorisations for three of the five products. One authorisation has no new buffer but the other has the buffer clearly defined. In 2017, both these legal documents are valid. As a result the manufacturers can pick which authorisation to follow, and are not required to put the new buffer requirement on the product label in 2017 so they haven’t.

Clomazone is very toxic to many plant species and there is a history of legal disputes relating to drift damage onto neighbouring crops. It is one of very few products that must be applied as a coarse spray. I have concerns about how this grey area between CRD authorisations and product labels, both of which are legal documents, could potentially be viewed by a court of law should a serious legal dispute occur.

So, to finish, can I make a plea for more decisions to be made? Around the world and increasingly in the UK, no-one, even if they have the power to do so, wants to put their head above the parapet and say this is how it will be. Personally, it gets to the point that I almost don’t care what the black and white decision is but, please, please, make it and give us all a less grey world.

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What makes rotations tick?

Posted on 14/08/2017 by Jim Orson

I have written before on Salle Farms in North Norfolk and their experience of introducing a seven year rotation around the turn of the century. It replaced a variety of short intensive rotations that were employed in different parts of the estate. The crop that seems, in particular, to benefit in terms of yield comparisons with both national and regional performance is winter wheat. This is now grown either two times in the seven years or three times depending on the date of the sugar beet harvest.

Some of the increase in yield may be due to reduced levels of black-grass but I do not think this explains everything. Hence, the magnitude of the relative improvement in wheat yield compared to other crops was a bit of a mystery to me until someone sent me a paper from the Journal of Ecology. This may start to provide a basis for an explanation.

The paper reports on an investigation into how soil biota may over time influence changes in plant species on uncropped land. I found the paper challenging to read but there was some clear guidance as to how soil fungi and bacteria may influence the relative growth rates of different plant groups. One of the main conclusions was that wild grass species are particularly reduced in growth when grown in soil that is inoculated with the biota extracted from soil that has previously just grown the same species. Hence, winter wheat may not grow so well in soil where wheat has been recently grown due to the soil biota that it encourages or the loss of organisms that are inhibited. In addition, the paper also reports that grass growth (and so perhaps wheat growth) is better when the soil contains a greater variety of soil biota left after growing a range of crops.

I have always been led to believe that the reduction in yield of wheat in wheat intensive rotations is by no means all due to take-all and it seems that the rest of the reduction could be due to other unidentified soil biota.

The overall conclusion of the study is that all the plant groups studied grow better in soil that has just previously grown other species because of less net negative effects of soil biota (in grasses) or because of more net positive soil biota effects. This may provide a more scientific basis to crop rotations and indicates that increasing the number of species grown in a rotation, perhaps including cover crops, may be better for the growth of all crop plant types.

Another conclusion in the paper is that the growth of plant species that tend to first infest bare soil, which have high root length and low colonisation from arbuscular mycorrhizal fungi (AMF), particularly suffers when they are grown in soil inoculated with the biota that they encourage. Oilseed rape fits this description and this may explain the NIAB TAG results that show that yields decrease as the intensity of its cropping increases. This latter research does identify two species of soil biota that are associated with intensive rape cultivation and may be the cause of the yield reduction. It is not clear whether this is because of direct effects via the crop roots or because they out compete other more favourable species.

                        Impact of rotational intensity

A recent review of the role of AMF and the impacts of agricultural management highlights the very negative effects of intensive soil disturbance and fertilisation on AMF. The review states that the fundamental principle of crop rotations is to exert a control function that prevents particular AMF from dominating the soil matrix. The review explains that continuous wheat favours the selection and proliferation of less co-operative and more aggressive AMF species. These are likely to enact behaviour similar to parasitism. Hence, at least in some circumstances, there can be ‘bad’ AMF species as well as ‘good’ AMF species. It goes on to say that this effect can be toned down by ‘break crops’, such as Brassicae (e.g. oilseed rape) or legumes. Brassicae are non-mycorrhizal crops which act as inhibitors of the dominant AMF species proliferation and legumes are AMF dependent crops which favour the overall propagation of AMF communities.

Complicated isn’t it?! New laboratory techniques are revolutionising research into soil biota and so I hope that we are now on the cusp of a better understanding of how crop rotations tick.

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The anatomy of high yielding crops

Posted on 28/07/2017 by Jim Orson

A few years ago NIAB TAG and FAR had a joint trial series on maximising wheat yields in England and NZ. FAR is the Foundation for Arable Research, the levy board in NZ responsible for cereals and a range of other crops.

The same varieties were grown in both countries. These were the highest yielding in each of the respective variety lists. High yielding sites were chosen and the intensity of use of crop inputs investigated. The components of yield, i.e. ear number, grains/ear and grain weight, were among the factors recorded.

The years in which the trials were held were not conducive to record yields but plot yields of up to 17 t/ha were recorded. The trials in NZ had more grains/m2 with higher ear numbers/m2 but the number of grains/ear was less than in England. Their higher yields were due partly to an increase in grains/m2 and, at least as significant, was that their thousand grain weights were superior. I cannot provide the precise results because the NIAB TAG membership paid for the English trials.

This example again shows that wheat is a wonderfully flexible crop. This flexibility comes in useful in a number of ways and shows why we can achieve reasonably good yields from year to year despite the variability in weather.

The question is why do they tend to have higher ear numbers and less grains/ear in NZ? I think we have to assume that this is an effect from weather and perhaps the following graph of average temperatures offers some explanation. I have shifted the monthly averages for Christchurch on the South Island of NZ by six months to allow for an easier comparison.

Jim Orson blog 200

As you can see, NZ has a warmer winter, spring and early summer. This, along with their higher levels of solar radiation, perhaps encourages robust tillering and tiller survival, resulting in more ears/m2. The late autumn and early winter for their 2017 crop was particularly warm, which may have helped Eric Watson establish a sound base to his world beating crop. Similarly, the high yielding UK crop in 2015 followed a mild winter.

The main period when grain numbers are determined, between the third node stage and flowering, is likely to be shorter in NZ because of their warmer conditions. The impact of this shorter period may be offset by higher levels of solar radiation and so the warmer conditions may not contribute to a lower number of grains/ears. It may simply be that their lower grains/ear is due to the increased competition as a result of higher numbers of ears/m2. Should competition be the explanation then this may well be a barrier to even higher yields.

Temperatures in NZ and England are more comparable during the period of grain fill when, logically, the higher levels of solar radiation in NZ result in higher thousand grain weights.

This explanation of the difference in the components of yield in NZ and England sounds very plausible. However, I have learnt over the years that seemingly logical explanations may distract from greater truths and the search for answers should ideally reach beyond simple analyses.

Unfortunately, despite being in different hemispheres, the harvests in NZ and the UK have overlapped this year. The weather in NZ has been very wet in recent months and some farmers are still trying to harvest their grain maize. Our own harvest is also being frustrated by rain and I hope that there will be a more promising weather forecast by the time this blog is on the NIAB website.

There is more on NZ crop production in my blog posted on 3 March 2017. 

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Wheat harvest 2017

Posted on 14/07/2017 by Jim Orson

It is the time of year when I try to predict the yields of the wheat harvest. Usually I do this in early July but the timings of the blogs have meant that this year it is mid-July. It is going to be an early harvest for many and so we will soon know the true picture. Everything seems to be early in Cambridge this year. I was lifting potatoes on the 1st June and my tomatoes were ready to pick on the 10th July.Wheat harvest

Where wheat crops had established well in the autumn, they came through the winter full of promise. Overall, it was a dry winter and so there was little waterlogging. If anything the winter was perhaps too warm but up to around the first node stage, wheat development is controlled mainly by day length which prevents crops becoming too advanced. The high yielding crop of harvest 2015 also experienced a warm and dry winter. Average temperatures in 2017 were also higher than average from April onwards, which has led to an earlier grain ripening.

Spring 2017 was exceptionally dry. Now I know that high yielding wheat years tend to have dry springs but it can be too dry leading to a reduction in yield potential. This may have been true in some parts of the country this year but the rainfall was so variable as to make it difficult to say which locations were most severely affected by drought. Rain did eventually arrive in May but in some areas there was not enough to alleviate fully the drought pressure.

Sunshine hours tended to be average or above average for every month bar February. There were really no exceptional months during the 2017 harvest year. This is unlike harvest year 2015 when April received far higher than average sunshine hours and solar radiation, particularly in the areas that achieved the very high yields. Overall, June sunshine hours were greater in 2015 than in 2017 except for East Anglia, the South East and parts of Southern Britain.

The final weather feature of note was the extreme heat in mid-June in some of the main arable areas. Temperatures were above 30 centigrade for three consecutive days and the nights were very warm too. This level of heat can cause a permanent reduction in the rate of grain fill as well as shorten the period of grain fill.

The higher than average temperatures may have reduced the period of grain fill by 4-5 days this year. In addition, the warmer weather also reduced the time between the third node stage and flowering when the potential number of grains sites is established. The percentage reductions in the times spent in these development stages may not have been compensated for by the average to above average radiation levels. Hence, in some areas this may have resulted in lower than average levels of intercepted solar radiation during these key stages.

So what are my conclusions? 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. It is a very difficult year to attempt to predict wheat yields and I am by no means confident. So much depends on how the levels of soil moisture affected growth in individual locations. I hope I am wrong and that everyone has a great wheat harvest!

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World wheat record

Posted on 30/06/2017 by Jim Orson

Eric Watson, who has just broken the world wheat record with 16.791 t/ha, stayed with us over the weekend after Cereals. He spoke at a seminar at NIAB on the Friday and we visited farms over the next two days.

I first visited Eric and Maxine in NZ around 20 years ago. It was clear to me then that they could break the world record if they were prepared to go through the bureaucratic process. Their farm has superb soils, their weather (plus irrigation) supports very high yields and their attention to detail is amazing. At that time, Eric was about to take the decision not to have root crops and onions on the farm because of soil damage, either from intensively working the soil or due to trailer traffic.

The soil in the high yielding parts of the farm is 30-40 cm of superb silty loam over around a metre or so of silty clay loam. It is then very gravelly. I am particularly interested in the soil type in terms of the nitrogen dose used for the world record yield. Some people express surprise that they used ‘only’ 258 kg N/Ha applied as urea treated with a urease inhibitor. I think Eric was also surprised because he had used more in previous years but is now convinced that the higher doses may have been inhibiting yield rather than encouraging higher yields.

The record breaking crop followed after a two year break from cereals and the previous crop was beetroot for seed. The soil mineral nitrogen (SMN) was 109 kg N/ha which firmly puts the field in nitrogen index 4 in the new RB 209. Soil tests indicated that the level of mineralisable N was 40 kg N/ha, although such analyses may not be very accurate.

I think that in RB 209 the soil type would be classified as a deep silt. In this case it recommends 100 kg N/ha for an 8 t/ha crop and 200 kg N/ha for a 13 t/ha. There are no yield adjusted recommendations above 13 t/ha but if the same rule of an extra 20 kg N/ha is applied for every tonne above 8 t/ha then a 16.8 t/ha should receive 280 kg N/ha. The crop would receive 245-255 kg N/ha using the NIAB TAG recommendations. Of course we do not know the actual optimum for the world record crop but its protein content was around 11%, suggesting that the dose was approximately correct. It is comforting that these two UK systems recommend similar levels of nitrogen to the approach adopted in New Zealand to produce the record yield. Perhaps we are making some progress at last.

In the world record crop, the total nitrogen removed in the grain was 319 kg/ha. This suggests that the combined amount in the grain and the straw was over 400 kg N/ha. Once again this demonstrates that in high yielding crops the efficiency of use of applied N and SMN is well above average and also that net nitrogen mineralisation can often exceed that estimated. All this helps to explain why using average data in a balance sheet of nitrogen supply and requirement for potentially very high yielding crops often recommends far too high nitrogen doses. Hence, previous experience in field trials still provides the most reliable guide to recommended nitrogen doses; albeit, this is an admission of our failure to understand sufficiently soil processes.

Finally, food for thought… The yield map of the world record crop shows that there were significant parts of the field approaching 20 t/ha. The lower yielding parts of the field tended to be in straight lines showing the impact of the tramlines and/or the wheelings of the linear boom irrigator. The NIAB TAG guidelines take such yield variation into account and assume that significant areas of a ‘X’ t/ha crop will have yields of ‘X+2’ t/ha. The other thing to take from the yield map is that there is more to come!

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