NIAB - National Institute of Agricultural Botany

Orson's Oracle

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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Past, present and future of KT

Posted on 13/07/2012 by Jim Orson

Despite the weather forecast we attended the first day, and sadly the only day, of the Great Yorkshire Show. It was crowded and the weather held until mid-afternoon, and in that rain-break I briefly read about the conclusions of the Defra Green Food Project. So, for me, the day provided a link between the past, present and future.

Many county, including the Yorkshire, and local agricultural societies were established in the 1830-40s; the Royal Agricultural Society of England in 1838 and Rothamsted in 1843. This was a time of greater domestic demand for food from an increasingly urbanised society - but before the steam engine had enabled the opening up of the Ukraine and the prairies and the cheap international transport of agricultural produce.KT in practice at NIAB in 1922 - discussing the impact of drought on potato trials

However, internal communications were rapidly improving through better roads and the establishment of railways. So there was an emphasis on and a reward for domestic food production. Improved communications not only meant more efficient transport of produce but also that farmers could get together more regularly to discuss the latest techniques.

It was really the start of what we now call knowledge transfer (KT), with the agricultural societies and shows playing a key role.

It was also a time of great technical innovation, particularly the understanding of soil nutrients, increased mechanisation and installation of field drainage. Coke of Holkham established better farm practices based on the Norfolk Four Course Rotation which was developed by ‘Turnip’ Townshend on the nearby Raynham Estates.

‘Turnip’ was perhaps the first great agronomist; he worked out how to crop all the land without having to resort to fallows and used the invention of perhaps the first great ‘tyre kicker’, Jethro Tull, in order to drill cereals and turnips in rows. This made it easier to weed crops and soon the horse hoe was introduced.

Coke established model farms, i.e. demonstration units, and open days, and farmers flocked to attend. As always, attendance was bolstered by the offer of a free lunch - nothing changes.

However, Coke complained that his ideas only spread by a mile a year, so KT was a problem even in those days and is a salutary lesson for those still seeking the ‘Holy Grail’ of KT. Some of the issues of KT were evident from Coke’s efforts. His system was great for the light soils of north Norfolk but perhaps less pertinent to heavy soils. I can imagine a couple of heavy land farmers kicking the soil at Holkham and saying it was not for them, but what a great lunch!

The reality is that there is no single ‘one-fits-all’ approach to KT; all that can be hoped for is that it is appropriate, timely and well co-ordinated. Each farmer and adviser is different and requires knowledge packaged in different ways. Some take more cognisance than others of what other farmers are doing; some are more risk-takers than others etc.

Researchers have been known to complain about poor KT preventing their pet projects from being adopted without thinking either about the risks involved or about the ease of management. Sadly, some researchers only present current findings in such a way as to try to secure further funding - farmers and advisers are very good at spotting that behaviour. Indeed, many of those responsible for KT in the past have underestimated the farmer’s and adviser’s ability to judge what they are seeing, reading or hearing and to assess if it is appropriate for their own businesses.

Well, that’s dealt with the past and perhaps a bit of the present. So what of the future? The Green Food Project is all about how increasing productivity can be balanced with improving the environment i.e. sustainable intensification. Now there’s a challenge for KT!

However, the authors fully acknowledge the future role of farmers and advisers in this process and have used the term Knowledge Exchange rather than KT. Other parts of the report suggest that as our climate gets warmer we may be growing more exotic crops such as chickpeas. I hope they’re easier to harvest than field peas or a year such as this will sort them out.

Our personal links with the past and future at the Great Yorkshire Show were reflected in our purchases. My wife bought me a liquorish whirl; a good and now traditional product of Yorkshire. I bought some rather nice olives; a new crop for the UK?

Finally, in this blog I may have overplayed the role of the UK in the development of farming systems. I say this because I was made aware of a salutary lesson a few years ago when visiting a research farm in a part of Australia well endowed with rainfall but not having the ability to get the water away from the fields. So they started to grow wheat on raised beds to increase the ‘freeboard’ for the cereal roots. A young researcher told me that she was excitedly explaining this new approach to some Chinese agronomists who quietly explained that they’d been doing the same for the past 1,500 years.

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This year’s wheat yields will be...?

Posted on 06/07/2012 by Jim Orson

I am sorry for the delay in writing this blog. Last weekend we met up with one of our daughters and her family. I think it was our 7-month old grand-daughter who gave me the sickness bug. Let’s say it was not the most successful of weekends away.

Despite feeling rotten (as only a man can) I managed to keep in touch with Steve Dorling of the University of East Anglia by e-mail. The reason for this communication was that on average (there are lots of assumptions in this blog, so beware) the end of June is halfway through grain fill of wheat. Steve had kindly offered to update me on the solar radiation and temperatures during this period (June 10th – 30th). You may remember that I talked of the importance of these two factors on grain fill in my blog ‘A late winner’ a couple of weeks ago.Wheat grain

Well, thanks to Steve, I now have the data for this first half of grain fill from two centres, at Wattisham in Suffolk and Watnall in Nottinghamshire, over the past 10 years.

I’ve compared this data with the regional wheat yields over the same period - my first observation is that in every year, except 2010, there has been typically 10-20% more radiation at Wattisham, near Ipswich, than at Watnall. Not only that - there is less year to year variation at Wattisham.

Steve explained that in the summer there is typically less convection and less cloud development the nearer you are to the coast due to cooler air temperatures; as I write, the sea temperature in the North Sea is still only 15°C!

This may partly explain why the Suffolk Hanslope clay soils yield more wheat than the Cambridgeshire Hanslope soils. Or perhaps that’s insulting the superb agronomic skills of the Suffolk farmer!

The second observation is that the good yielding years appear to have a minimum of average radiation for the site and below average temperatures at night. I emphasise that I’m only talking currently about the first half of grain fill and perhaps I can prepare a blog at the end of grain fill to give a more complete story.

The exception was 2011 - which seemed to have superb grain fill conditions with higher than average radiation and low temperatures at night, but below average yields. I think we all know what happened here - the early spring drought took its toll on the number of potential grain sites.

One of my first blogs a few months ago explained why we got yield responses to chlormequat in the absence of lodging in 2011. This plant growth regulator ensured that more grain sites survived that drought and this resulted in a yield benefit because the grain fill conditions were so good.

So what of 2012? Well, radiation so far at Wattisham has been just less than average for the site. However, radiation at Watnall has been very low, nearly as low as in 2007 (the time of the Hull floods). And, whereas night temperatures at Watnall were high in 2007 they have been low in 2012. Similarly, night temperatures have been low in Wattisham in 2012.

This seems to suggest that conditions for grain fill up to the end of June have been OK at Wattisham, but not good at Watnall. This is providing all things are equal. However, can all things be equal in a year when we have seen a huge challenge from BYDV, lorry loads of black-grass and fungicides only being able to damp down rather than control diseases?

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The bleeding edge?

Posted on 27/06/2012 by Jim Orson

Over the last month black-grass control experiments have been assessed and demonstrated. There is no doubt that the Flowering black-grassissue is how to control the weed with herbicides in dry autumns. We are now so dependent on the pre-emergence and early post-emergence herbicides and typically they will not work anywhere near their best when seedbeds are dry.

In addition, in many cases we have the legacy of a high seed return this year. The whole industry really knows what to do about it but many are looking for new and quick solutions. A quick solution would be a new and effective herbicide. We have known for years that this would not be the case. Until quite recently many farmers still firmly believed that the chemical companies were holding something back.

I have had queries about alternative approaches. Weed wiping has been suggested but there are severe practicalities in keeping the wick from touching the crop. Some farmers are suggesting that the industry should be allowed to return to straw burning. I do not think that this will provide all the answer, even if it were allowed (which, I am sure it won’t).

I was a technical adviser to MAFF when the ban was being discussed. There is no doubt that in many circumstances straw burning would provide some advantage and this was one of the arguments which was presented to MAFF. However, public sentiment was totally against burning.

What interests me is the current debate on the impact of direct drilling on black-grass populations. The impact of primary cultivation on black-grass numbers was assessed in the LINK funded series of trials on the greater understanding of the agro-ecology of the weed. Adopting the Simba Solo resulted in the highest black-grass numbers and the plough resulted in the lowest numbers. Direct drilling was somewhere in between.

So direct drilling was by no means the disaster that some had predicted. There could be several reasons for this. One is that much of the freshly shed black-grass seed is lost from the soil surface. A few years ago The Chadacre Agricultural Trust and The Morley Agricultural Foundation funded a PhD on losses of grass weed seeds from the soil surface. Losses were very significant in the autumn and winter but it was difficult to gauge the role of the different factors. There was, for the first time, the suspicion that some black-grass seeds were eaten by predators, possibly birds.

I believe that the proponents of a straw rake to encourage losses of seeds have a case. Pot trials show that black-grass seed germinates and establishes much faster if buried at a depth of 1 cm (0.5 inches) rather than lying on the surface. This may increase overall losses despite burying the seeds away from the soil surface where they are vulnerable to some losses.

In terms of chemical control with soil acting herbicides, one potential advantage of direct drilling is that the seedling and secondary roots of black-grass may be closer to the soil surface when compared to other approaches to primary tillage. Such differences could be of greater importance where there is significant resistance to the herbicides and when conditions are marginal for herbicide activity.

Of course, there is direct drilling and direct drilling. There is a huge difference in the level of soil disturbance between the different types of drill. This has resulted in observations that more black-grass survives between the row of some types of drill and along the row with other types of drill. This aspect could be critical in the longer term. Attention to detail is now the order of the day.

There are, of course, possible downsides to direct drilling. By treating only plants from seed shed in the previous crop, the further development of herbicide resistance will be maximised. This is assuming that resistance can get worse! In addition, there could be some unforeseen circumstances. In Australia, millipedes and earwigs have built up to such high levels in long term direct drilling that they are now damaging crop plants. I am not saying that this would occur on the UK, what I am saying is that there could be problems that we would not have predicted.

However, we will get an early warning because some UK farmers have been direct drilling over the last 10 years or more. Let us hope that they will be on the ‘leading edge’ rather than the ‘bleeding edge’.

If you want to get really depressed, listen to the black-grass blues

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