NIAB - National Institute of Agricultural Botany

Orson's Oracle

Is arable farming going to hit the buffers?

Posted on 04/10/2012 by Jim Orson

We now have a few new registrations coming through that have been completed since the HSE’s Chemicals Regulation Directorate (CRD) introduced its interim arrangements on assessing aquatic buffer zones.

The new product Teridox (dimethachlor) has a buffer zone requirement of 10-metres and the new Hurricane (diflufenican) labels will have a buffer zone requirement of 12-metres. Dow claims that Dursban (chlorpyrifos) would require a 72-metre buffer zone according to the method of assessment that’s being used under the interim measures. Under the interim arrangements buffer zones wider than 5-metres cannot be reduced under any circumstances, but they are only necessary when there is water in the ditch.

These are worrying buffer zone widths and all kinds of issues arise from this situation.

First of all, are the new widths based on good science? I know that the basic drift model used to develop the original LERAPs scheme was based on a narrow boom width sprayer travelling slowly. Drift from sprayers travelling at 12-14 kph is undoubtedly higher. So there may be some logic in the wider buffer zones from that point of view. But the question has to be, has something been identified that suggests that current buffer zones and application techniques are causing a problem?

The only information I can find on the likely scale of any problem is dated 2010 and says that only 1% of surface water bodies monitored by The Environment Agency are failing their Environmental Quality Standards for pesticides. This is a low level of failure, but of course any failure has to be regretted. However, a failure may have been due to pesticides moving to water through the soil or on the soil surface rather than spray drift.

Buffer stripsMonitored water-bodies tend to be lakes and rivers and not small ditches on farms. So the question is whether farm ditches, which may have water in them from time to time during the year, contain a viable aquatic ecosystem that requires an aquatic buffer zone to protect them? The French authorities appear to be of the opinion that this is only seen with larger on-farm streams and water-bodies.

The other issue is whether mitigation will eventually be introduced so that these newly introduced buffer zones that are wider than 5-metres can be reduced in the future. Let us hope so. The great thing about the original LERAPs scheme was that it rewarded good practice by allowing a reduction in buffer zone width due to the adoption of lower doses and/or reduced drift spraying techniques. This resulted in many farmers using the lower drift air induction nozzles for nearly all spraying operations and there are now other engineering solutions that could further reduce drift, including improved control of boom height. Let us hope that good practice will eventually be rewarded when the arrangements are finalised.

There are other mitigation methods that also need to be investigated. Drift studies are carried out where there is very short vegetation, but there is some evidence that taller vegetation in the buffer will trap a very significant amount of drift. This also offers the opportunity for a bit of joined-up thinking because such vegetation, correctly managed, may also be a large step forward for biodiversity.

Some farmers think that one way forward would be to use adjuvants to reduce drift. This is a minefield as an adjuvant may reduce the drift for one product but may increase it for another; the ultimate minefield would be when tank-mixes are used.

The graph shows the impact on land availability for food production of wider buffer zones. Paradoxically, it is those farmers who have ‘done the right thing’ for biodiversity who are the ones that will be most penalised because they haven’t created large fields by ‘piping-in’ ditches and removing hedges.Impact of buffer zones on arable land availability

I recognise that this is the worst case scenario because I’ve assumed a buffer zone on every side of the field but you get the ‘drift’ (sorry about the pun). It is sobering fact to mention that our high yields mean that for every hectare of cereals not produced in this country a few hectares will have to be grown elsewhere in the world. It is beholden on us not to export environmental impacts to other countries.

There are other implications as well. Farmers, where they can, will avoid those products with wide buffer zones, and not just on the fields that have ditches that may have water in them at the time of application. This is because of the way that arable farming now has to work - spray operations are pre-planned and appropriate to not just one but a number of fields. Hence, there could be more reliance on fewer modes of action and an increase in the risk of pesticide resistance.

So, there’s a lot to play for and we look to the regulators to consult widely and to develop a simple but scientifically robust solution that meets the concerns of the farmer and the conservationist as well as the consumer who is reeling from higher food prices.

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A non-event

Posted on 28/09/2012 by Jim Orson

Last week something did not happen. Let me explain what I’m talking about and why it’s heartening news.

In the middle of last week I suddenly started to receive emails suggesting that there was going to be a major announcement the following morning on a refereed paper that suggested that rats fed on GM maize were more likely to develop tumours than those fed on conventional maize.

The press conference was timed in order that it could feature on the lunchtime news broadcasts. So the next day I sat down to listen to the lunchtime news and there was no mention of the paper. Similarly, there was no mention in the evening broadcasts. The next day this refereed paper was only given some credence in the Daily Mail, but not so on their website.

Now if this scientific paper was published a few years ago there would be widespread coverage in the press about the dangers of GM. So why didn’t it get the coverage last week? There may be a few reasons, including a changing press and public opinion on GM. However, there is also, in my opinion, a gradual recuperation in the reputation of and respect for good science.

In March 1996, the British Health Minister announced that a committee of scientists set up to advise the government on spongiform encephalopathy issues had linked an unusual outbreak of a human degenerative neurological disease to BSE. The politicians had said that such a link was impossible. They stated that this was based on scientific opinion but of course no scientist had said categorically that this could not occur. So science and scientists, unjustifiably, got it in the neck both from the media and the general public. There then followed a long period when there was a high level of distrust of scientists, something that was latched upon by the anti-GM movement.

The start of the recovery of the reputation of science was, in my opinion, as a result of the Lancet article in 1998 in which Andrew Wakefield claimed that there was a link between the MMR vaccine and autism. These findings were based on unsound evidence and in 2004, fellow authors of the Lancet article issued a retraction. In-between the two dates there was considerable media support of Wakefield. He was seen by the press to be a whistle-blower standing up to the state machine. However, in 2010 the General Medical Council concluded after a two and a half year hearing that Wakefield had acted unethically, dishonestly and irresponsibly. Shortly afterwards the Lancet fully retracted the article from its online version.

Science reporters now deeply regret their coverage of the MMR issue and seek to listen to other views before jumping to lurid headlines. This is what happened last week. At the news conference reporters even quoted the comments and concerns of other scientists on the paper. Their access to other views did not occur by chance but through the good offices of the Science Media Centre who circulated the paper, at very short notice, before the press conference to the relevant scientists for theirinformation and comments. It turns out that there were real concerns about the science and these were expressed at the press conference and were obviously not well defended by the speakers. Subsequently, the French author of the paper has refused to release the raw data of the study to the European Food Standards Agency, which is not a position that instils confidence in his findings.

So I think science is now in a much healthier place than a few years ago when any bit of questionable science could unjustifiably grab the headlines. The press conference was arranged by a leading figure in the anti-GM movement and now perhaps that movement will have to accept that questionable science does not lead to a progression in public debate. It only devalues their reputation. Many thanks to the Science Media Centre for ensuring such a balanced debate.

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Loose connections

Posted on 20/09/2012 by Jim Orson

The last couple of blogs have been about black-grass alongside field size and biodiversity. There’s a rather thin thread of a connection between the two subjects. Are the current issues over black-grass control going to result in more spring-sown crops?Spring barley

A recent BASF survey of farmers’ attitudes to cultural control of the weed suggests that we are indeed going to see more spring-sown crops. The most likely scenario is that this will mean more spring barley as it has the most agchem control options for black-grass that’s emerged in the spring in response to the cultivations involved in establishing the crop.

Those farmers who have recently grown spring barley as a cultural control option for black-grass have been pleasantly surprised by the results they have achieved. Whether this is because of better machinery achieving a more reliable crop establishment than in the past or because we’ve had a run of relatively dry springs remains to be seen.

Now the connection with biodiversity! It was the effective control of black-grass and other grass weeds that led to the huge adoption of winter-sown crops in the 1970s and early 1980s, at the expense of spring-sown crops. And this increase is considered to be one of the main reasons for the reduction in biodiversity, particularly farmland birds, over the last few years.

So the likely trend to an increase in spring barley at the expense of winter wheat may be good for farmland birds? Well, it could be but spring barley now is not what spring barley was in the 1970s. It is now sown earlier, typically in February to very early March rather than mid to late March in the 1970s. It also receives more nitrogen and weed control is generally more effective; it’s the uncontrolled spring-emerging broad-leaved weeds that can benefit biodiversity.

Spring barley is deemed to be more skylark-friendly than winter wheat because the spring canopy is not so high or dense, particularly beneficial for the second and third clutches of eggs. However, early-sown spring barley that’s received a fair dollop of nitrogen may not be ideal.

Going back to the BASF survey, it seems that farmers are seriously considering all the more effective cultural options for black-grass control. Spring cropping is perhaps the most effective option with experience suggesting that two consecutive spring-sown crops is extremely successful. Ploughing is generally less effective than sowing spring crops but is being seriously considered by a significant proportion of farmers. Less effective is delayed drilling, but again some farmers are seriously considering this option. I assume that the extent of the problem is determining which option individual farmers may take.

Like many, I have serious concerns over the delayed drilling option. It may be a good option for an acreage equivalent to a couple of days drilling but perhaps not for the entire wheat area. With only two days drilling to do it is possible to hold back where conditions aren’t wet until the five-day weather forecast suggests that the seed is better in the ground!

A strategic use of delayed drilling is particularly useful in a very dry autumn. In such conditions there’s not the urgency to drill earlier, partly because there may be poor crop emergence, plus the pre-emergence black-grass herbicides will not work effectively in such conditions. Assuming that the worst black-grass fields are left to last, this approach means that the herbicides may likely be applied to moist seedbeds and certainly closer to when the soil surface becomes moist. I realise that this is all a bit easy when sitting in an office but it is worth thinking it through.

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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.

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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.

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