NIAB - National Institute of Agricultural Botany

Orson's Oracle

IT and reducing pesticides in raw drinking water

Posted on 16/11/2015 by Jim Orson

This is continuing the theme of my previous blog. It summarised some of the very sensible and practical approaches that can be taken to reduce pesticide movement to water in order to meet the very demanding targets set by the Drinking Water Directive (DWD).

Research in France over the last twenty years and practical experience in the UK show that pesticide choice and dose is not such a significant issue in meeting the DWD standards when the soil profile is relatively dry at the time of application and there is no significant rain for at least a week or so following application. The issue of pesticide choice and dose becomes critical when the soil profile is close to soil moisture capacity at application, particularly if it rains within a few days after application. In France there are guidelines on pesticide choice and dose where the soil is relatively dry and where it is approaching soil moisture capacity. These guidelines make interesting reading, particularly because they are derived from field experimentation rather than modelling.

It is also interesting to note that in field trials in France there has been more pesticide movement to water in some Integrated Pesticide Management approaches, when compared to more conventional treatments. The explanation is obvious. The conventional treatments were applied when the soil profile was reasonably dry but the IPM treatments involved delayed autumn drilling and pesticide applications were made to a wetter soil profile. Although less pesticide was applied in the IPM treatments they resulted in more pesticide movement to water. This goes back to the dilemma of what we are trying to achieve with IPM, namely a reduction in pesticide use or a reduction in pesticide impact. This example demonstrates that reducing pesticide use does not necessarily mean reducing impact and I hope that our researchers have the nouse to aim for a reduction in impact rather than use.

There are some situations in the UK where there can be a very real conflict between optimising pesticide performance and reducing pesticide movement to water. The clearest example was covered in the previous blog. Propyzamide is an essential element in black-grass control in autumn sown oilseed rape and it has to be applied to wet and cold soils to optimise control. Subsequent rain can mean huge (in terms of the DWD) spikes in propyzamide levels in the water courses feeding water works although such levels comply with the Environmental Quality Standards. Whilst buffer strips, particularly in high risk fields, will reduce surface run-off, the movement through the soil to field drains can alone cause spikes.

It is absolutely essential to reduce the size and number of these spikes which can result in the closure of water works until the content supplied to domestic users meets the DWD standard. It seems to me, and this is not an original thought, that a way out is to try to close off the intake of the water works during the few hours when the spike occurs in addition to the other stewardship guidelines issued by the pesticide and water companies and the Voluntary Initiative. This is more difficult than it seems. First of all the water company has to be able to shut off the intake i.e. be able to supply water from another source or have reservoir storage it can utilise whilst the intake is off. Unfortunately, these facilities are not available at all water treatment works. The water company then needs to know when and where the propyzamide is sprayed and then it has to calculate the travel time of the spike to the intake of the water works.

The latter is getting more possible with more understanding of pesticide movement to water but locating when and where propyzamide is applied remains a difficult issue for water companies. Perhaps help is at hand with so-called ‘crowd-sourcing’ software on mobile phones. NIAB TAG is pioneering such an approach in order to improve further the services to its farmer subscribers. It was first tried last April by asking farmers the stage of flowering of their oilseed rape in order to improve the prediction of sclerotinia risk. Each farmer’s response was automatically geo-referenced and within a few hours the map in this article was achieved. NIAB TAG is rolling out other uses for this approach and it is envisaged that the information provided can only result in more precise and timely advice.

Whilst I realise that NIAB TAG members have a common cause for taking part in crowd-sourcing approaches, I would suggest that farmers in the relevant catchments have every reason for working with water companies in a similar way in order to reduce the problem of spikes of pesticide content in the raw water entering water works.

Crowd Sourcing

IT can also help by providing improved field specific advice. The WaterAware app. from Adama is an encouraging start but its designers accept that improvements are needed. Nevertheless, it gives the platform for the farmer or adviser to assess the risk of pesticide movement to water on a field by field basis through geo-referenced information on soil type and weather. Such an approach will still need the expertise of the farmer or adviser in order to make final decisions but it should lead to an improvement in decision making.

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Pesticides in water – meeting the challenge

Posted on 02/11/2015 by Jim Orson

It is now the time of year when there is concern about pesticides moving to water and exceeding the challenging limits specified in the Drinking Water Directive. The maximum level for an individual pesticide is 0.1 µg/l (0.1 parts per billion) when measured at the tap i.e. after processing at the water works. This is not based on risk to human health and the environment but the limit of detection when the Directive was first introduced. The industry has long argued against this limit but I suspect that it is here to stay.

The real concern at this time of year centres on the slug pellet metaldehyde and the oilseed rape herbicides carbetamide and propyzamide. Metaldehyde cannot be removed from water by the processes that are adopted in water treatment works. On the other hand, with these oilseed rape herbicides any small exceedances of the level specified in the Drinking Water Directive can be reduced by water treatment to meet the requirements. The real problem is the large spikes of concentrations in the water following rainfall shortly after application. An example is given in the graph below, in this case propyzamide. Without these herbicides it would be difficult or impossible to grow winter oilseed rape in the vast majority of situations and so a solution has to be found or the area of oilseed rape grown in the UK could be significantly reduced.

There is a huge effort being made by the pesticide manufacturers and The Voluntary Initiative to provide guidelines on how to reduce levels in raw potable water. This involves the use of buffer strips, identifying high risk fields, weather forecasting and specifying best practice etc. However, it is a difficult problem to overcome.

There can be conflict between getting good pesticide activity and reducing environmental impact: propyzamide offers a good example. The requirements for good activity are a moist and cool soil. This means that applications are made as soon as the conditions are suitable, often in early to mid-November. Not only are soils already moist at application but the fact that everyone tends to spray in a small window means that large peaks in the content of propyzamide can occur in raw potable water. Such peaks have resulted in water treatment works being closed down for a couple of weeks.

So, what is to be done? I recently attended the BCPC Brighton Congress and the session on the Water Framework Directive (that includes the Drinking Water Directive) provided some direction. There was a brilliant talk by the lead catchment scientist of a very large UK water company. This included targets for their catchment management initiatives. It is the first time I have heard a water company declare their targets and such statements are a real help to those working to reduce pesticide movement to water.

One target is that the maximum levels of metaldehyde in raw potable water should not exceed the 0.1 µg/l limit. It is a sensible target because this pesticide cannot be removed at the water works. The second target is to reduce peak pesticide peaks in water by half. In my opinion this is a realistic target and, if it is shared by other water companies, gives me hope that the industry can rise to the challenge without too much disruption.

All the current and future initiatives on the management of those herbicides which are likely to move to water should, if adopted, enable us to creep closer to reducing pesticide peaks by half. Notice that I said ‘if adopted’. The water companies are still supporting voluntary measures but these have to reap results. Unfortunately, this may mean that some farmers will have to compromise on cropping choice and management if they have high risk fields. However, there may be alternative ways of tackling the problem which could result in less disruption to farmers. I will investigate these in a later blog.

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Wheat yields – not just a great summer

Posted on 16/10/2015 by Jim Orson

My blog in early July suggested that yields might be good except in those parts of the country where a very dry May/June could limit the yield potential on all but the most moisture retentive soils. This was along the right lines and yields have been exceptionally high in some areas but the dry conditions in May/June perhaps did not limit yields as much as I thought they would.

So I have revisited some of the weather data I reviewed for the July blog in order to try to explain the exceptionally high yields experienced by some growers. Unfortunately, I am still pursuing solar radiation data that is hard to come by and will continue with my quest. In the meantime I thought I would set out my preliminary thoughts in this blog.

The solar radiation data that I have, and which does not cover some of the extremely high yielding areas, suggest that it was well above average for the whole growing season. However, it was not exceptionally high during grain fill.

Overall, temperatures from January to July were very close to average for the arable areas of England. In the July blog I noted that the cool nights in June could be beneficial only because the crop would not respire overnight so much of the gains made during the day. These cooler than average overnight temperatures were a particular feature in North Yorkshire and Northumberland where some of the highest yields occurred. These areas also had good levels of rainfall in May/June.

What may also have been very significant in determining yields this year was the higher than average amounts of solar radiation in March, April and May. The amounts in April were exceptionally high. This may have resulted in higher than average levels of tiller growth and survival, grain sites/ear and stem reserves. Hence, it may be reasonable to suggest that the higher yield potential established in the spring was realised by much better than average, but not exceptional, conditions during grain fill. It is interesting to note that a recent AHDB (the old HGCA) Project Report 496 suggests that modern wheat varieties have higher levels of stem reserves than those introduced over a decade or two ago.

My July blog suggested that overall yields would be higher north of the Wash because of rainfall patterns and the fact that temperatures on the 1st July were not as exceptionally high as those which occurred further south. We will never know the impact, if any, of that very hot day on final yields.

So it seems that there was no one standout feature that resulted in the very high yields this year. On the other hand, the weather throughout the year favoured high yields. The crops wintered well, with little or no waterlogging, and experienced very favourable weather in the spring and summer, except in those areas which suffered from drought stress during May/June.

There will be another blog on this issue when I have more data on the structure of some of the very high yielding crops and on the weather, particularly solar radiation.

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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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