NIAB - National Institute of Agricultural Botany

Orson's Oracle

Dormant good news?

Posted on 13/09/2012 by Jim Orson

Scientists and editors spend hours upon hours writing reports. This is true for all levels of science, including the applied research that may be of direct value to the farmer. So how many of these reports do you read or is it that much of this effort is potentially wasted? If there is an element of wasted time, is there a more effective way of recording the research and presenting the results?

Looking on the HGCA website there have been nearly 500 project reports written. Have you looked at any at all or do you rely on someone else to do it for you or for HGCA to come to you with the ‘messages’? Who prepares these ‘messages’: the scientists who have carried out the research or someone who is more dispassionate about the findings? I say this because scientists are naturally enthusiastic about their research and think that all their findings must be of great value to the industry.

Well, I’m as guilty as most in not even looking at the majority of the HGCA project reports. But I do read some; particularly those which cover subjects that get widespread publicity or the results of which I consider may change practice.

It is for this reason I have just read ‘HGCA Project Report 498: Dormancy in grass weeds’ (well not all of it). It covers black-grass, so I think that this comes in the category of a subject that is getting publicity rather than it being the basis for large changes in practice. This is because practice is dominated by greater issues, such as labour and machinery costs and risk management.

The report does contain some really interesting stuff - well interesting to a black-grass nerd like me! It reinforces theFlowering black-grass messages from earlier research that soil moisture status is more important than dormancy in determining time of black-grass emergence. It also supports the contention that later drilling in the autumn is more likely to be successful in low dormancy years in reducing black-grass plants emerging in the crop.

However, reading reports often means that individuals identify different messages to those of the authors. This year dormancy is very high; not surprising with the awful weather when the black-grass seed was ripening. This is being portrayed by some as bad news. On the other hand, this report provides data to support the previous slim evidence that high dormancy results in a significantly lower proportion of seed establishing plants in the first autumn after shedding. There is a penalty for this as high dormancy also means that a relatively high proportion of freshly shed seed being able to establish plants in the autumn of the following year. However, by that time it will have lost its dormancy and be anxious to grow quickly.

So there may be a shaft of light in the blackness that surrounds the control of this weed this coming season. The exceptional levels of dormancy this year may result in a relatively low proportion of the equally exceptional levels of seed shed this summer establishing plants. Mind you, you would be a brave person to try to control with herbicides alone the level of black-grass that may still be expected in a huge number of fields this autumn.

All I am saying is that emergence this autumn may not be as bad as might have been expected from the amount of seed that was shed this summer. This is reinforced by the fact that there may be few additional plants emerging this autumn from seed shed last year. Whilst the dormancy of last year’s seed was high the numbers shed were generally very low.

As always with biological systems there is the ‘it depends’ factor. As you know, nearly all black-grass plants are derived from seed in the top 5 cm (2 inches) of consolidated soil. So all the issues surrounding black-grass plant emergence depend on where in the topsoil the black-grass seed is located.

Leave a comment / View comments


Field size and biodiversity

Posted on 03/09/2012 by Jim Orson

Some new houses are being built close to us and there has just been a delivery of bricks. The lorry was large and had an equally large trailer and in-between the two was a mini-crane to lift off the pallets of bricks.

This is quite a coincidence as I was just about to start to write a blog about the impact of field size on time required for cultivations: the basic principles for achieving efficiency in both delivering bricks and cultivations are the same. I’m sorry but this is beginning to sound like the start of a sermon!Drilling combinable crops

It’s all about the absolute rate of cultivation (forward speed x width of the cultivator) or the amount of bricks carried by a lorry adjusted by the amount of downtime. The downtime for both the lorry and the tractor is driving to and from the site, or field, and also the time on the site for the brick lorry to unload or for the tractor and cultivator to turn.

Once the cultivator is in the field, the influence of the proportion of total time spent turning on work rate becomes less important as its value falls. As an example, assume that a cultivator that doesn’t have to turn at all can cover 8 ha/hr. The work rate would fall to 4 ha/hr if it spent 50% of its time turning. Decrease the turning time again by 50% and the work rate would increase to 6 ha/hr, an increase of 2 ha/hr. A further 50% decrease in turning time increases the work rate by 1 ha/hr. So it is the classic law of diminishing returns; as fields get progressively larger the increase in work rate gets progressively less because the influence of the turning time is reduced.

Armed with this principle, I spent a few hours in a field last week measuring the forward speed and width of a cultivator to get the absolute work rate and the turning time to get the level of downtime. I measured turning time by using two approaches and they gave me the same answer, which was a relief. I then calculated the impact of field size on work rate. Naturally you have to make some assumptions on field size and I assumed square fields where the dimensions of the area that can be cultivated were a multiple of the width of the cultivator.

The reason I did this exercise was because I was asked by an organisation interested in biodiversity what was the impact on field size of machinery requirement. Farmland birds do like smallish fields and a mosaic of crops, because this type of countryside provides habitat (more field boundaries), and some bird species don’t like to fly too far from the nest to forage for food. Many will only forage over a distance of about 300 metres.

Bearing this theoretical model for increased biodiversity in mind, the maximum size of field should be about nine hectares, ensuring that one dimension of the field will always be less than 300 metres, and there should be no block-cropping; the approach the industry has taken in order to reduce the journey times to individual fields.

I was asked the same question many years ago and looked at some old Silsoe reports that suggested, in terms of work rate of machinery, that perhaps the ideal individual field size was around 30 hectares (75 acres). As I assumed that this was calculated using smaller tractors pulling narrower equipment than today, I considered it needed updating - hence my ‘time and motion study’.

The result of my study was that the advantage for machinery work rates of having fields above 30 hectares was fairly limited. I tried different scenarios and was surprised how little forward speed or machinery width influenced this conclusion. So the old Silsoe reports are still valid.

The operation I witnessed was a 4.5 metre wide disc and tine machine cultivating stubble down to a depth of around 12 cm with a forward speed of 7.655 kph. By my calculation, it takes around two minutes (or 10%) more time/hectare to cultivate a nine hectare field rather than a 30 hectare field; this doesn’t take into account the extra time spent moving between the smaller fields. Work rate for a 90 hectare field is about 5% higher than for a 30 hectare field.

This increase in work rate between nine hectare and 30 hectare fields doesn’t sound a lot but increasing labour and machinery costs/hectare by at least 10% is by no means insignificant. Plus, smaller fields mean more land and costs devoted to field boundary vegetation, typically hedges, and higher yield losses and management time associated with the increase in the area of headlands. Removing the option of block cropping would result in even higher costs for the farming operation.

In the end, I suppose your view on this information will depend on your view of countryside management. The view of those who wish for more biodiversity in the countryside may be that this is a small price to be paid but, of course, there may well be alternative and less economically damaging approaches to increasing the biodiversity of arable land. These alternative approaches need to be debated and tested.

Leave a comment / View comments


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.

Leave a comment / View comments


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.

Leave a comment / View comments



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!

Leave a comment / View comments


Page: ‹ First  < 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 >