NIAB - National Institute of Agricultural Botany

Orson's Oracle

The value of a day’s delay

Posted on 02/10/2015 by Jim Orson

We got up at 2:30 a.m. the other day to view the eclipse of the super moon. The fact that we had a good view of the event meant that the sky was clear. The weather was set fair and so I knew that cereal drilling would soon be going ahead at a frantic pace.

Do not take this wrongly but I was hoping for another few days of delay in drilling winter wheat. Wet weather delayed drilling until about 10th October in 2009 and ensured high levels of black-grass emergence prior to that date. This was also the first autumn of the wider adoption of stacking of the pre-emergence herbicides. The resulting black-grass control was generally more than satisfactory. The level of control was attributed by many to the stacking of the pre-emergence herbicides but the involuntary adoption of the cultural control measure of delayed drilling also played a significant role.

After a wet spell there is always the temptation to get on the land and drill before it is really suitable. The most extreme case was in the autumn of 2000 when it seemed to rain almost every day. Surveys of NIAB TAG members clearly showed that those who puddled-in wheat that autumn had inferior yields to those who waited for the better soil conditions in the first couple of months of 2001.

What has always amazed me is the rate of reduction in soil moisture below a depth of 30cm. One day the spade would tell me it was too wet to cultivate but the next day it seemed dry enough to cultivate. Salle Farms in Norfolk, which keeps meticulous records, have shown that for a few days yields increase with every day’s delay in drilling after a sodden soil starts to dry.

Now, there is data to demonstrate the impact of leaving the soil just another day (see the diagram) or preferably two days before wheeled or tracked vehicles run over it. This data was collected by the University of East Anglia as part of their government funded research project, the Demonstration Test Catchment study of the River Wensum in Norfolk. It shows the rapid drying of the medium textured soil at 30-50 cm depth between 5th February and 6th or 7th February 2013 despite little change in the moisture status of the shallower layers. As farm equipment has got heavier over the years this information takes on added significance in trying to avoid compaction in the deeper layers of the soil.

The take home message is quite obvious, do not rush back onto the land as it starts to dry after it was sodden. A day or two’s delay may be handsomely rewarded in terms of crop yield. Regular use of a spade will only confirm the message and improve decision making. So keep digging.


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Top shelf reading

Posted on 16/09/2015 by Jim Orson

Farmers Weekly has been moved to the top shelf at our local shop (Waitrose). I am not sure why. Is it because of some risqué language in the livestock section or the frequent mention of (oilseed) rape in the crops section? Or is it because the powers that be at Waitrose have read the popular book by Yuval Noah Harari entitled Sapiens: A Brief History of Humankind? Naturally, there is a reference to agriculture in the book. The Guardian (I am not a regular reader of the paper) review of the book includes the following paragraph:

It's a neat thought that "we did not domesticate wheat. It domesticated us." There was, Harari says, "a Faustian bargain between humans and grains" in which our species "cast off its intimate symbiosis with nature and sprinted towards greed and alienation". It was a bad bargain: "the agricultural revolution was history's biggest fraud". More often than not it brought a worse diet, longer hours of work, greater risk of starvation, crowded living conditions, greatly increased susceptibility to disease, new forms of insecurity and uglier forms of hierarchy. Harari thinks we may have been better off in the stone age, and he has powerful things to say about the wickedness of factory farming, concluding with one of his many superlatives: "modern industrial agriculture might well be the greatest crime in history".

I am not sure what Harari means by modern industrial farming but it would appear to include both organic and conventional farming. This is because both forms of arable farming typically include growing grain crops.

Nor is Harari alone in these thoughts. I recently went for a check up at the doctors and whilst waiting my turn, I picked up a copy of The Ecologist. The main article stated that we would all be better off if we returned to being hunters and gatherers. Amazingly my blood pressure was at a reasonable level when tested a few minutes later!

wheatI am not sure where to begin in commenting on these thoughts. Humans were not tempted by the devil to grow wheat. They grew wheat because it offered them a better way of life; being able to put down roots and have a more reliable diet. Long hours would also be spent hunting and gathering and I suspect the limited amount of food available ensured that there was no risk of an over-crowded planet! I am sure there must have been a greater risk of starvation and malnutrition in the Stone Age. Living off the land is a romantic notion but the reality is rather different.

An ever increasingly efficient agriculture has released an ever increasing proportion of the world’s population to escape from what is often the day to day drudgery of producing food. It has afforded authors the education and the time to write books decrying current food production methods.

There is a whole spectrum of opinions on agriculture in society. I note that the new shadow Defra secretary is a vegan. She believes that eating meat is harmful to people and the environment. In some ways it is and it is true that significantly more resources are required to produce a kg of meat than a kg of a vegetarian or vegan alternative. It is just possible that if all humankind gave up eating meat, organically grown crops could feed the world, although there would be increased concern over food security.

However, all these noble notions cannot override the reality of the will of the people. The last leader who tried to force a rural idyll on his country was Pol Pot and look what happened there.

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GM back in the news

Posted on 03/09/2015 by Jim Orson

It is a fair time since I had a rant about GM. I am not alone as the following quote from a recent opinion piece in The Times demonstrates:

‘The debate around genetically modified crops would almost certainly puzzle an alien. “I don’t get it,” he’d beep, arriving on his first tour of Earth. “You’ve found a way to boost crop yields and reduce your reliance on pesticides. Repeated, peer-reviewed scientific studies have shown there is no downside. It could be the answer to a pending crisis of global hunger, with no ill-effect. Yet it still makes lots of people very angry, and many governments avoid it in horror. Why?’

It is very easy to answer that question. There are too many organisations who have pinned their reputation and, in some cases, their finances on being against the technology. It has also become an ideological struggle against ‘multi-nationals’. Hence, the same old scares are repeated and new issues are exploited as being evidence against the technology. A prime example is the reducing numbers of the monarch butterfly in the US. These iconic butterflies migrate in the autumn from southern Canada and northern US to a specific area in central Mexico in huge and spectacular clouds.

Monarch butterflyThe monarch butterfly first entered the GM debate when it was found that they died when contained in chambers heavily laced with pollen from Bt maize modified to control corn-borers. This is no surprise; if you continually expose an insect to very high levels of something that is known to kill it, it will die. The key issue is in real life would the monarch butterfly be exposed to sufficient amounts of this pollen to affect its health? The judgement of the experts is that it would not.

Despite this, there have been recent headlines that GM Bt and glyphosate tolerant maize is responsible for the recorded decline in the Monarch butterfly. However, looking behind the headlines is a more nuanced explanation. Monarch butterflies feed exclusively on native milkweeds (Asclepias species) and cannot survive without them. Native milkweeds are perennials that flourish in semi-natural areas such as road sides, edges of fields and also in uncropped land. The plant declined by 58% in the plains states from 1999 to 2010. Monarch populations dropped by 81% in the same period.

It now seems that the major factor in the decline of milkweed is that more land is now cropped with maize in order to supply the ethanol plants. Nearly 4.5 million hectares have been taken out of the Conservation Reserve Programme, much of it going into maize. It has to be acknowledged that glyphosate tolerance enables a higher level of control of native milkweeds in maize but the shift into maize and out of something akin to set-aside has been a major factor. This is an unintentional consequence of promoting biofuels.

Another reason for the fall in the population of the Monarch butterfly may be illegal logging in Mexico where it overwinters on trees. The logging was almost halted at one stage but there are recent reports that it has recommenced.

Taking the populist decision to ban GM, as the Scottish Government has done, is an easy way out for European governments. They are really abdicating their responsibility to lead the debate rather than just blindly follow public prejudice that has been stoked up by misleading and misinterpreted information. It seems that getting a better balance between crop production and biodiversity is ever more challenging and it is my view that GM technology can play a role in improving the chances of getting it right.

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Extreme weather

Posted on 20/08/2015 by Jim Orson

There was some interesting weather in the UK in July. The 1st was the hottest July day on record and a temperature of only 10C was recorded in Powys on the 31st. However, the extreme event of note for me was the overnight thunderstorm on 16th/17th in Cambridge. Up to that point, I was desperate for rain in order to perk up our garden and allotment. We had had rain forecast several times but received tiny amounts, if any at all. As they say in Norfolk, “it never rains in a dry time”.

Unfortunately we were away when the thunderstorm occurred and so I did not experience it at firsthand. The first I knew of it was when I checked the online weather station in Cambridge the following morning (I was that desperate for rain!). It said that there had been a total of over 50mm of rain overnight. When we got back on the 18th, I cycled up to the allotment where my rain gauge had recorded 80mm of rain. Up to 90mm was recorded locally. It must have been an amazing storm to witness.

This got me thinking about the challenges from weather events to our crops and their management. The dull and wet summer of 2012 was one such seasonal extreme event. It took a large toll on wheat yields in some parts of England, particularly on the heavy clays. I also clearly recall the dry and hot summer of 1976 (it was actually very dry from June 1975 to September 1976). It is not just the extreme summer weather events that can impact on our wheat crop; the wet autumn and winter of 2000 reduced the yields achieved in 2001. However, despite what we sometimes consider to be extreme weather variations, UK wheat yields are amazingly consistent from year to year when compared to some other parts of the world.

One notable example of large variations in yield over the years is in parts of Australia. There is an area in Victoria, north of Bendigo, called the Mallee, which is perhaps close to being marginal for arable crop production. Harm van Rees, a leading Australian agronomist, recently sent me the following data on its growing-season rainfall (GSR) expressed as deviation from average (rather than ‘of average’ as stated on the y-axis). As you can see, there have been a very high number of dry seasons over the last 15 years or so and the ten year running mean (the red line) is still going down. In the very dry seasons, wheat yields can be alarmingly low (often below 1.0 t/ha) or zero and many farms are in financial crisis. There was a similar but shorter downward trend of the ten year running mean in the 1940s. The anxiety about the current trend is heightened because of the concern over the possible influence that climate change may have been having on the rainfall in recent years and may have in the future.

So what would you do in this situation? Not an easy question to answer. Australian researchers have developed sophisticated risk management tools for use in arable farming, many of which are now based on seasonal forecasts. For instance, these help to decide on how much nitrogen to use as applying any nitrogen in a very dry year can reduce wheat yields as well as unnecessarily increase costs. A preliminary analysis suggests these tools are beneficial when compared to adopting the same management each year. As one researcher points out “the [seasonal] forecasts are too good to ignore, but not good enough to completely rely on. Even though there are uncertainties, we do have more information than if we were guessing by chance.” However, what farmers and bank managers in the area featured in the rainfall graph really need is a reliable forecast of rainfall not just for the season but also for the next few years.

A recently published report called Extreme Weather and Resilience of the Global Food System warns that major “shocks” to global food production will be three times more likely within 25 years because of an increase in extreme weather brought about by global warming. So we will have to accept that there are going to be even more challenges in the future. Achieving more resilience in our production systems to extreme weather events will have to be given a higher priority. It does not help the UK industry that pesticide resistance and legislation are together impacting on the resilience of our arable systems. It is also regrettable to have to say that opposition to GM may well reduce our ability to respond to the challenges of the future. The report can be found on

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The maths of black-grass control

Posted on 06/08/2015 by Jim Orson

This is my 150th blog and perhaps too many have been on black-grass, the nation’s most talked about weed. You have to believe me when I say that I was trying to avoid writing about this weed yet again but recent press results have driven me back to the keyboard.

The issue that I would like to raise is the too simplistic conclusions made from field data. These can over-estimate or under-estimate the role of cultural or chemical control of the weed. Good field data is not easily achieved and it is the industry’s responsibility to use it intelligently.

I have written before about the huge fuss made a few years ago about increased crop competition from wheat being able to reduce black-grass seed heads by half. Many took this as the answer to the black-grass problem but the maths of the weed’s dynamics told us differently. Models suggest we have to chemically control 97% of black-grass plants emerging in a continuous wheat crop grown in ‘normal circumstances’ in order to contain populations at current levels. This means that we can let only 3 out of 100 plants make it to seed shedding. Crop competition does not reduce black-grass plant numbers but reduces the ability of the plant to set viable tillers. Hence, reducing seed heads per plant by half through crop competition means that we can allow 6 rather than 3 out of 100 plants to make it to seed shedding. So a 50% reduction in seeding per plant reduces the need for chemical control to 94% rather than 97% control. Every reduction in the reliance on chemical control is useful but this is not the game-changer that was originally claimed. Obviously, greater reductions in seed return through competition would reduce the need for chemical control by a greater percentage. However, more than a 90% reduction in black-grass seed set from increased competition will be required to get down to a chemical control requirement of 70% of plants; a level that is now often achieved by pre- and/or early post-emergence herbicides.

This is an example of when a large percentage figure can over-estimate the value of a control technique. In contrast, recent quotes in press reports seem to be under-estimating the benefit of stacking herbicide products to control the weed. Some say that using more than two products in a mix adds little to the percentage control of plants. These statements can undermine the value of using mixtures of three or more products.

The best way to explain what I mean is to give an example. Let us again assume that there are potentially 100 black-grass plants/m2 that will emerge in a winter wheat crop. A two-way mix applied pre-emergence may control 60 of these plants (i.e. 60% control) and a three-way mix may control 70%. This is ‘only’ a 10% increase at face value. This does not sound a lot and some might say it would be better to apply this third component early post-emergence where potentially it may give a higher level of control. The maths of this situation are illuminating.

In this example, the two-way mix will reduce the numbers in the crop from 100 plants/m2 to 40/m2 and adding the third component of the mix will reduce the numbers from 40/m2 to 30/m2. Reducing survivor numbers from 40 to 30 is in fact 25% control, which is a lot higher than the headline figure of an additional 10% control. Put another way: using a two-way mix pre-emergence would let 40 plants/m2 survive and achieving 25% control from an early post-emergence would provide the same result of a final plant number count of 30 plants/m2 (more than 29 too many!).

I realise that this is a rather simplistic view and herbicide resistance will ‘nuance’ the situation. We know little about the impact a particular pre-emergence application will have on the susceptibility of weeds to a particular early post-emergence application. Are the percent controls of plants achieved by individual products simply additive or does an earlier application pre-dispose its survivors to be more or less difficult to control with an early-post emergence application?

What I am saying is that data need to be carefully interpreted. In practice, it may be that stacks of more than two products applied pre-emergence are particularly relevant to later sown winter wheat crops provided the seedbed and the weather are conducive to good control. Simpler mixes may be more suited to pre-emergence or peri-emergence applications to earlier sown winter wheat crops, particularly when the weather and/or seedbed are not suited to good control, with an expectation that a further application of a mix could well be necessary early post-emergence.


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