NIAB - National Institute of Agricultural Botany

Orson's Oracle

The precautionary principle

Posted on 23/08/2012 by Jim Orson

I was not a great fan of salads when I was young. Now, I really enjoy them, particularly at this time of year when they are made mostly from things I’ve grown in the garden and on the allotment. The crowning touch is the dressings made by my wife, who now incorporates this year’s taste sensation in the dressings - balsamic vinegar glaze.

Eating salads can be hazardous. Last year 31 people died in Germany, and over 1,700 were made very ill, by eating organic bean sprouts served in a number of restaurants. In 2006, four people died in the US from eating organic spinach. All these deaths were attributed to E. coli. There is currently, due to concerns over E. coli, a massive recall of conventionally grown lettuce produced in California and delivered throughout the US and Canada.Market stall

California is well known for its draconian pesticide laws. In Europe, we have the prospect of key pesticides that have been used safely for years and years being withdrawn because they may be defined as hazardous under the new EU pesticide regulations.

Electricity is hazardous but the risk of using it is well tolerated by society. Hence, society already embraces the safe use of materials that are hazardous but this uniquely does not apply to pesticides, to the extreme anger of the scientific community. I assume the phrase ‘the precautionary principle’ was used to argue for the hazard cut-offs in the new European pesticide regulations.

Well, some strains of E. coli are clearly hazardous and there are systems set up to minimise the risk. No doubt these are being strengthened as a result of the types of these headlined incidents. I dare say that some strains of E. coli are much more hazardous than the pesticides that are likely to be withdrawn because of the artificially set hazard cut-offs in the new pesticide regulations. This is despite the fact that there is no evidence that the risk is unacceptably high when these pesticides are used in practice. It all sounds like dual standards to me.

Perhaps the discrepancy in the way these risks are viewed is due to the fact that pesticides are synthetic chemicals whilst E. coli is natural. However, as they say, anthrax is natural!

I can’t claim to be a scientist, but having had scientific training I can often identify discrepancies in attitudes within the various forms of agricultural production. A striking example was when I last worked in New Zealand. Whilst I was away in some distant part of the South Island, my wife attended a ‘Women in Agriculture’ meeting. It was a visit to an organic farm where they were told, rather piously, that the nutrients for the system were supplied by collecting leaf litter from nearby forests.

Just let us think about that a minute. The natural nutrient cycle of a forest is disturbed to provide nutrients for an organic farm! Surely there are less harmful ways of supplying these nutrients. I suspect that the use of ‘conventional’ fertilisers may be far less damaging to the environment.

Whilst I recognise the concerns expressed by some over the production of food I’m also appalled at the statements by some single interest groups that unjustifiably foster fear and reinforce ill-informed and unscientific perceptions. This spills over into regulations. As a result, we may unjustifiably lose valuable pesticides and we still await the widespread adoption of GM crops in Europe. I can foresee that in a few years time there will be questions as to why we were so slow to adopt GM technology. By that time, of course, the single interest groups will have moved onto new ‘issues’.

Can I finish on the subject of salads, particularly cucumbers? We have only two plants but they are churning out at least a dozen cucumbers a week. We give some away but we still have a surplus and cucumber soup features strongly in our current diet! By the way, due to the precautionary principle, no animal manures are used in my garden or allotment because I grow a wide range of produce that is eaten cooked and uncooked. It is impossible to limit animal manure use solely to those crops that are cooked before being eaten.

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It’s obvious, isn’t it?

Posted on 15/08/2012 by Jim Orson

I have heard or read two things in the media over the last few days that struck home. The first was on the radio about a joke T-shirt worn by someone on the Google campus. It went something like ‘those who claim they know everything really annoy those of us who actually do’. It reminded me of the well known phrase ‘the arrogance of science’.

The second was an article on scientific fraud in the Sunday Times. It claimed that some scientists are sociopaths. That had me running to the dictionary (well, Google again). The definition of a sociopath can be summed up as someone without a social conscience.

So, how good is the science that supports products and decisions taken by individuals and governments? Do vested interests corrupt the messages coming from the data in order to prove that they really do know everything or is the data itself sometimes fabricated? The Sunday Times article suggested that even fabricated data has been the source of peer reviewed papers. The people (or sociopaths?) doing this are either anxious to make a name for themselves and/or to get the next bit of research funding.

Does this happen in agriculture? Well, I hope not but there is always the tendency to look at data in a way that favours your own personal opinion. This is only natural but some describe it as a vested interest. As the Sunday Times loftily quotes, the only vested interest of science should be the uncovering of the secrets of nature.

So, how should this issue be tackled? Some are asking for some kind of commission to follow up the concerns expressed by scientists and others on particular research findings. Apparently there is such a body in the USA. However, much of the concern can be overcome by letting other scientists have access to all the data to interpret and also the ability to do follow-up research to confirm (or otherwise) the data itself. This of course assumes that others have the time, the facilities and the funding to do such things. The concern is that these prerequisites are getting increasingly scarce in agricultural research. On the other hand, information technology has made it a lot easier to transfer and re-analyse data.

There have been ‘issues’ between scientists and agronomists in agriculture but these tend to have arisen for entirely innocent reasons. What is more, they have been overcome through transparency and follow-up research. One of the most notable examples was about controlled drop application (CDA) of pesticides. It is an attractive theory. Avoid the too small drops and the too large drops that are contained in a conventional spray and you have the ability to reduce volumes and even reduce doses. Scientists recorded significantly more pesticide on the target with this method of application.

However, when agronomists tested CDA in the field, they became aware of shortcomings. Dose for dose efficacy, at best, was no better than conventional nozzles. Weed control under a thick crop canopy was worse than with the conventional nozzle. These findings led to great friction between the scientists involved with the concept of CDA and agronomists. However, this led to very constructive discussions between the two ‘sides’ which resulted in follow-up projects that showed, amongst other things, that the quantity of the dose on the target was not the only determinant of efficacy. It was also about where on the target the pesticide was deposited. CDA is very good at getting pesticides on the horizontal surfaces of the target whereas the vertical parts of the target are the ones where pesticides often exhibit the most activity. Hence, the follow up research generated key information for the future; true progress.

I should say that this does not mean that CDA does not have a role in agriculture. Sales of equipment, particularly overseas, demonstrate that it has a real role to play in specific circumstances.

However, this all goes to show that however good the scientists, they do not know it all, even if their reports and talks suggest they do. It is beholden to the rest of the industry to test what they tell us. Above all scientists, like farmers, need to show humility towards the natural world.

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Exceptional!

Posted on 06/08/2012 by Jim Orson

Initially, Mrs Orson and I were disappointed to get tickets for only one of ouJess Ennisr three carefully chosen athletics sessions at the Olympics. However, it soon became clear that we were lucky to get any at all. This luck was compounded by the fact that the tickets were for the night that Team GB won three athletic gold medals. It was an extremely noisy, dramatic and unforgettable experience. The media described it as historic. That’s perhaps a bit strong but it was truly exceptional. How lucky we were!

Also exceptional was the rainfall for the three months from mid-April to mid-July. When I started to think about its implications on the nitrogen status of crops and soil, I asked Rothamsted Research for a view. I think I’ve said before that the behaviour of nitrogen in the soil is fiendishly difficult, even impossible, to grasp but Rothamsted has been researching this subject since 1843 and know more than anyone else.

The (very rapid) response is intriguing and I should like to thank Keith Goulding and Andy Whitmore for their help. I should also point out that neither has been at Rothamsted since 1843, but Keith has been there since 1974!

The possible scenarios I had in mind were that excessive rain may have caused leaching of applied nitrogen; the rain-induced lush growth may have increased potential nitrogen uptake; the constant moist state of the soil may have resulted in more nitrogen being released (increased mineralisation); or that waterlogging may have caused losses through denitrification.

In today’s context, the latter has serious connotations. In anaerobic (e.g. waterlogged) conditions, bacteria convert nitrates and nitrites in the soil to nitrous oxide gas. During this process the main gas produced is nitrogen, which is inert, but a lot of nitrous oxide is also produced. This is a greenhouse gas 300 times more potent than carbon dioxide. So not only do we lose the major plant nutrient through this process but also the greenhouse gas output from cropping increases significantly.

The Rothamsted team kindly ran one of their models to see what the implications of the wet weather could be in the context of their own rainfall data and for winter wheat grown on their flinty silty clay loam. The results may surprise some. Leaching losses were only marginally higher this year at Rothamsted.

This sounds surprising but please remember that when it started to rain in mid-April the soil under winter cereals was very dry to depth. There needed to be a lot of rainfall in excess of transpiration losses before the drains actually ran. Even then, the applied nitrogen had to move a long way before it got into the drains.

The model also shows that crops had a reduced nitrogen status this year. Personally, I was surprised that I didn’t see winter cereal crops looking very short of nitrogen but on the other hand, they were not quite so dark green this year.

The main cause of any nitrogen loss since 1st March on a clay loam soil at Rothamsted was calculated to be denitrification; up to around 40 kg/ha of nitrogen could have been lost through this process. To put this into context, the same model suggests that the loss due to denitrification for the same time period last year was just 0.1 kg/ha of nitrogen.

Perhaps this exceptional spring represented the worst case scenario for this process and should be treated as a ‘one-off’? Soils were wet at a time when all the bag nitrogen had just been applied and also they were warm(ish), so bacterial activity was high. Logically, denitrification losses may have been lower on better natural draining soils and even higher on very heavy clays. Conversely, leaching losses may have been more significant on better natural draining soils.

This Rothamsted model also suggests that the soils were so waterlogged that there was insufficient oxygen for root growth. Perhaps this wasn’t so critical this year as the crops didn’t suffer any subsequent drought stress but it may have meant that the ability of the crop to scavenge nitrogen at depth was inhibited.

My next question to Rothamsted was what does this all mean for soil nitrogen levels this autumn?

The answer was that there are too many ‘ifs’ and ‘buts’ to be definitive two months in advance. However, it seems logical to me that there will not be a lot of nitrogen kicking around.

The problem with nitrogen is that logic does not always apply. To return to simpler subjects: it is certain that in two months time our ears will still be ringing from the crowd noise during Mo Farah’s last and glorious lap of the Olympic 10,000 metres final. Truly exceptional!

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Wheat yield prediction for 2012

Posted on 30/07/2012 by Jim Orson

A couple of weeks ago I summarised the weather conditions for the first half of wheat grain fill. There is a strong link between solar radiation received during this period and final yield. However, there are other factors at play, such as whether the crop has a sufficient ‘sink’ for the products of photosynthesis during grain fill, is there sufficient green leaf to absorb the radiation, and while the crop is not short of water whether the nights are so warm that the crop respires much of the gains of the day.

Hence, I am not so naïve as to believe that yield can be accurately predicted based on solar radiation intercepted by the crop during grain fill. For instance, we had great conditions for grain fill in 2011 but the wheat crops in the areas of the early summer drought had insufficient ‘sink’ (in this case lack of grain sites) to use all of the products of photosynthesis.

At first hand there appears to be no danger of lack of potential grain sites or an ‘overall’ sink in 2012. On the other hand fusarium in the ear may be affecting the final number of viable grain sites and high levels of septoria have resulted in less green area on the final three leaves.

On average there are about 660 day degrees (some studies have concluded a little longer) between flowering and maximum dry matter yield. This means that on average grain fill takes 42 days. I’ve assumed this year that this lasted from 10th June to 21st July inclusive for the following analysis. Whilst doing this, I recognise that this year has been cooler than average and so grain fill will take two or three days longer than usual.Ear of wheat

The data, kindly provided by Stephen Dorling of the University of East Anglia, comes from the two weather stations mentioned in my previous blog on the subject; Watnall in Nottinghamshire and Wattisham near the Suffolk Coast.

For those 42 days the radiation was about the same as in 2007, a relatively poor yielding year. We had sufficient rain in June and July in 2007 and so there was no great shortage of moisture during grain fill. However, we’ve had cooler nights in 2012 than in 2007 but crops were cleaner in 2007.

The big difference is that in 2007 we had a spring drought. There was no real significant rain in many areas for around six weeks from mid-late March. April was exceptionally warm and the crops were potentially on fire with brown rust. However, the crops did not suffer from the drought as much as they did last year.

So, where does that leave us? Some farmers are expecting tremendous yields this year. I’m not so sure; there are too many potential downsides. Hence, if I was to stick my neck out I would say that yields are not going to exceed the recent averages achieved. I hope that I’m wrong but if I’m correct - at least the prices are not too bad!

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Lovely crumbly soil

Posted on 23/07/2012 by Jim Orson

To sell or to incorporate straw is a debate that’s been slowly hotting up over the last few years. The heightened interest was caused initially by the dramatic increase in the cost of phosphate and potash. This year a shortage of good forage is enlivening the debate, and there is also a call by some excellent black-grass growers to enable some straw and stubble to be burnt in an effort to keep the weed under control.

Let’s deal with the last point first. Stephen Moss of Rothamsted Research says that straw burning, on average, controls around 40% of freshly shed black-grass seed, and it can be as high as 70%. That sounds impressive but it only partially lifts the pressure on herbicides. Perhaps of equal importance, the survivors can be stimulated to germinate. Hence, there is little doubt that straw burning would contribute to keeping black-grass under control, but it is likely that it wouldn’t make a hopeless situation manageable without the adoption of other cultural measures.Straw burning

Much of the debate on whether to bale or to incorporate straw centres around the possible delays caused by baling and carting which is likely to be more significant during a wet harvest, alongside the value of straw as a provider of plant nutrients. The additional field traffic, much of it out of tramlines, from equipment that may be fitted with road tyres could cause localised soil structure problems.

There is also the value of straw as a means of increasing soil organic matter, which has been the subject of a long term experiment at Morley. We started in 1983 comparing straw burning, baling and incorporation. However, over the past 20 years we’ve been investigating the value of straw produced from a range of nitrogen doses, ranging from 0 to 250 kg/ha, applied to continuous wheat. Obviously the plots receiving the highest doses of nitrogen have produced the most straw.

After around 20 years the organic matter is around 1.7% in the plots receiving the highest N doses and 1.55% in the plots receiving no N. It doesn’t sound a lot and some would say that, based on these data, the value of straw for increasing soil organic matter isn’t that significant. However, simple tests on the soil suggest that there’s a remarkable difference in the aggregate stability of the soil. In practice, this means that the soil is much more resilient to cultivations and rainfall and also, it may be easier to prepare a seedbed.

Can a difference of 0.15% in organic matter be that significant? Perhaps, but in my opinion there may be another significant factor - microbes! Incorporating organic materials, including straw, on an annual basis increases the soil biomass, which is made up of soil bacteria and soil fungi. These produce enzymes whose activity results in the production of substances that help to bind soil particles together into more stable aggregates.

There is a host of scientific evidence to support the value of an increase in soil biomass, as well as the practical experience of arable farmers when we first returned to straw incorporation in the early 1990s after years of burning. After only a couple of years, farmers reported that the land was much easier to work which was attributed to increases in soil organic matter. However, the organic matter difference would have been minute after just a couple of years of straw incorporation. The ‘workability’ must have been due to something else that can build up more rapidly than soil organic matter which I believe must have been soil microbial biomass.

Unfortunately, the increase in soil biomass from the incorporation of a crop residue lasts only around 18 months, so it has to be a regular practice to maximise its value. I’m not sure how persistent the effects are from incorporating organic manures. However, you know who to thank if you don’t have access to organic manures but you regularly incorporate your crop residues and the soil is in good condition. Soil organic matter is not everything.

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