NIAB - National Institute of Agricultural Botany

Orson's Oracle

Lost in translation

Posted on 05/04/2012 by Jim Orson

Being semi-retired has it advantages. During the recent warm and sunny weather we took off to London for the day. The morning was spent looking around part of the British Museum and for the afternoon we got last minute tickets for the matinee of a stage show. This was followed by a walk round St. James’s Park and dinner. A good day with good company (my wife checks my blogs for English and so I have to say that).

Rosetta stone
The three languages on the rosetta stone

At the British museum we saw the famous Rosetta Stone. Just to remind you, it was the key to the decipherment of Egyptian hieroglyphs. The inscription on the Rosetta Stone is a decree passed by a council of priests. It is the same script in three languages, in hieroglyphic (suitable for a priestly decree), demotic (the native script used for daily purposes) and Greek (the language of the administration). This enabled the literal translation of hieroglyphics into their Greek equivalent and consequently into modern day language.

Another aspect of working part-time is to keep up-to-date and so I was listening to the Archers omnibus edition the following Sunday. The Rosetta Stone was mentioned in the context of enabling the truth to be deciphered. Bizarrely, this got me thinking about nitrogen recommendations for crops.

Nitrogen processes in the soil are fiendishly complex and Rothamsted is still researching the subject, despite nearly 170 years of endeavour. That is not meant to be a criticism but a way of demonstrating the complexity of the subject. Leonardo da Vinci wrote 500 years ago that ‘we know more about the movement of celestial bodies than about the soil underfoot’. Even today we would say ‘he was not wrong’.

No doubt there are variations in the soil processes between and within fields and perhaps within individual square metres of fields. So how do we get nitrogen doses correct with this type of background? The task is made even more demanding because weather after application will affect the amount of bag nitrogen required.

The reality is that recommended doses are often a long way off the mark. So the task in hand is to minimise these errors. The key is how should we do it? What is the equivalent to the Rosetta Stone for nitrogen application?

As many of you know, despite the complexity of nitrogen use in the soil and by the crop, many current recommendation systems are based on a simple model. The model is that Soil Mineral Nitrogen is used by the crop at 100% efficiency and fertiliser nitrogen is used at 60% efficiency. This sounds a bit odd to many: why the difference in efficiency, surely nitrogen is nitrogen?

I think the basis for the assumed difference in efficiency goes back to a time when there was more potential for mineralisable nitrogen in the soil. This was because arable land typically had a recent history of grassland and/or regular use of organic manures. One way to take this into account was to assume a high uptake of the measured Soil Mineral Nitrogen to ensure that there was an allowance for a significant amount of net mineralisable nitrogen during the season.

However, this is not now the typical situation. The vast majority of arable fields have no recent history of grassland or organic manure use. NIAB TAG trials over the last ten years suggest that the efficiency of use of Soil Mineral Nitrogen by wheat is way below 100% in long term arable soils where organic manures have not been used. As I have previously reported, in Australia, where the majority of nitrogen for the crop is from the soil, they assume an efficiency of uptake of 40-50%.

Why is this important? The assumption of 100% efficiency of Soil Mineral Nitrogen and 60% efficiency of bag nitrogen results in a reduced recommendation of around 1.67 kg/ha (100 divided by 60) of bag nitrogen for every additional kg/ha of nitrogen in the soil. Hence, if the efficiency of Soil Mineral Nitrogen is in fact significantly less than 100% then there is a danger of recommending sub-optimal levels of bag nitrogen. This is particularly relevant for long term arable soils with nitrogen indices of 2 and above in RB 209 and where there is no recent history of organic manures. This includes wheat after oilseed rape.

As I am a rather pragmatic part-time agronomist I consider that actual trial results, with all their shortcomings, are the Rosetta Stone for nitrogen recommendations. These indicate that nitrogen recommendations for wheat after oilseed rape in the current edition of RB 209 are still too low. Hence, I believe that the simple assumptions adopted in many recommendation systems have led to something being lost in translation.

By the way, I really do not see the Archers as being at the cutting edge of agriculture but what are the chances of building the super-dairy at Ambridge? In such a politically correct programme I suspect the chances are zero!

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White on white

Posted on 30/03/2012 by Jim Orson

On MondWinter cereal sprayingay 2nd June 1975 it snowed in Suffolk. By the end of the week the temperatures were around 250C and remained so for weeks. The subsequent dry winter meant that there was still a significant soil moisture deficit at the end of February. The following summer of 1976 was hot and dry and there was no meaningful rainfall until September. Naturally, once it started to rain it didn’t know how to stop.

This was a real problem to those with irrigated potatoes. They were worth £300/tonne (remember this was 1976) and the land was too wet for the harvesters. Luckily, that autumn/winter was also mild and so they were harvested eventually.

The biggest problem then was the potential tax bill. In my opinion, much money was wasted on unnecessary expenditure in an effort to reduce it. Perhaps today more sophisticated ways of avoiding taxes would be adopted. But, I’m not going there!

So farming in extreme weather conditions is not new. However, we seem to have recently been experiencing more prolonged periods of rain…or drought…or high or low temperatures. Until it happened this year, who would’ve thought that there could be active brown rust in wheat around Newcastle in March?

How do we manage crops in such variable weather conditions?

With fixed costs, it’s important that such variation is borne in mind, and minimising labour and machinery for the fabled ‘average’ season will obviously not be the best strategy.

With our input management there are many issues to discuss on the requirement, timing and amount of individual inputs in addition to the overall strategy. For instance, seed rates can influence moisture loss from the crop, particularly if there is a dry winter. This may be critical if there is a dry ripening period. I remember seeing a winter wheat seed rate trial in New Zealand where the higher seed rate plots had ‘hayed off’ because of associated higher moisture losses at earlier stages of growth. On the other hand, reasonable seed rates are required to compete with herbicide resistant black-grass and to minimise the impact of tiller loss during a dry spring.

Last year we got yield responses to chlormequat use in winter wheat. This was because chlormequat increased the number of potential grain sites by reducing the loss of grain sites in the very dry spring. The increased yields came from the great grain fill conditions experienced in June and July which enabled these additional grain sites to be filled.

But it could have gone the other way. More grain sites than considered wise by the untreated crop at, and shortly after, the time of the application of chlormequat would have resulted in more ‘tail corn’ and lower harvested yields should the dry conditions have continued into June and July.

Perhaps my most sobering experience of the impact of drought on crop inputs was in 1976. Over the previous winter I, as a lowly ADAS district adviser, had had heated discussions with soil scientists on the optimum dose of applied N for wheat.

This was the time when yields were beginning to rise rapidly and I was convinced that the then recommendation of 125 kg N/ha was too low. However, I didn’t win the argument and recommendations for 1976 stayed the same. I had to be content with the knowledge that there were plenty of N trials in the ground and they would prove me right!

However, it was so dry that the optima in nearly all these trials were zero applied N. Presumably, the additional moisture loss from the extra green area created by applied nitrogen negated the value of its ability to trap more solar radiation. You must remember that we were then talking of yields of 4-5 t/ha.

One unexpected result from last year was that urea and ammonium nitrate applied during the extremely dry spring produced the same wheat yields. It seems that significant ammonia losses from urea will not occur until moisture starts to affect the integrity of the applied material. So losses can be minimal when applied in extremely dry conditions provided that there is sufficient rain when the drought breaks to quickly ‘wash’ the urea into the soil.

Conclusion: adjusting inputs to take into account more variable weather conditions is fraught with difficulty. It comes down to risk management based on experience, good information sources and sound science.

By the way, the reason why I remember the snow in June 1975? I was playing in a golf tournament at the time. For the less informed, you play golf with a white ball.

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Throw away the textbooks

Posted on 25/03/2012 by Jim Orson

Indulge me. Just one more reflective blog on Australian farming.

Tree ferns recovering from bush fireThe picture of the tree fern recovering from a wildfire is a metaphor for the resilience of the Australian countryside and agriculture. Perhaps the area of the least resilience is the small rural communities and towns. These are obviously suffering and there are many local initiatives to try and keep them in business, including promoting tourism and as a place to do business.

The problem is rural depopulation. Not only has agriculture become dramatically more labour efficient, but many farmer families, particularly those with children, have now moved to relatively large towns with good schools. So it is the farmer who commutes to work during the growing season, staying in the farmhouse when the long hours are required.

The more meetings I attended, and the more farmers I met, made me review my understanding of the management of risk in determining input levels. The risk of getting it wrong is fairly low in areas where the rainfall is typically either relatively high or relatively low.

In low rainfall areas, farmers are still reluctant to throw much at the crops, even when soils are moist at the time when inputs may theoretically increase yields. This is because of the high chance of a ‘dry finish’. In this situation, additional inputs can reduce yields if they have encouraged larger crop canopies leading to more moisture loss earlier in the season.

Risk management is at a premium in those areas where it is more likely that there may be sufficient moisture to keep the crop actively growing until ripening. Getting it right is crucial, because exploiting the good years and minimising losses in the bad years is critical to the long-term economic viability of these farms.

Since my first blog from Australia there has been too much rain in Queensland, New South Wales and Victoria in particular; between 240 and 400 mm of rain in a week. We only just got out of a small town in Northern Victoria in time; having to drive through shallow water on perhaps the only route still open.

In one way, this is good news as the soils will have high moisture reserves when sowing starts in late April. But, it is also bad news because waterlogging will result in nitrate leaching and denitrification. Soil mineral nitrogen is the major source of nitrogen for most Australian cereal crops and too much rain will have diminished this valuable resource. This only goes to prove the old adage that the weather is never perfect for farming.

The Australians have studied the availability of soil mineral nitrogen in detail, because of its importance. They reckon that between 40-50% of it in the rooting zone is taken up by the crop. Our RB209 and some other UK recommendation systems assume that there is 100% take-up of soil mineral nitrogen. I regretfully have to admit that a review of around 60 NIAB TAG trials in wheat suggests that the Australians have got it right (this once!!!).

Finally, I’ve previously listed the potential threats to Australian crops. Not only is it the weather (drought, heat and frosts) but an array of pests. One morning, we actually drove through a small flight of locusts, and find out that they can easily block car radiators.

There are a couple of pests I’ve previously not mentioned. Earwigs and millipedes are severely damaging seedling crops in some areas. The textbooks say that they should not but since when have Australian pests read the textbooks.

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Europe rules - OK?

Posted on 16/03/2012 by Jim Orson

The wheat belt in Western Australia is vast and not what I envisaged at all, expecting large, flat and square fields. The fields were large...but they were certainly not flat or square.

In fact the landscape was very similar to the rolling English countryside, except nearly all the trees were eucalyptus and the fields were white, either because they were stubble or droughted grassland. Many of the fields contained trees that can’t be removed without permission; if it was permissible to remove them part of a deal includes planting other trees elsewhere.

The same rules on tree removal seem to apply in other states. I stood in a 1,000-acre field in South Australia that must have contained at least 50 individual trees. This must reduce the intended efficiencies of scale, but Google Earth has resulted in greater vigilance by pressure groups. Yes, Australia also has pressure groups, in this case literally tree-huggers.

Drought in Australia

In one of my meeting’s with local farmers an unexpected issue was raised. In Western Australia there is the prospect of selling non-GM canola (oilseed rape) to Europe at a very attractive premium. However, to achieve the premium the crop has to be grown to some ‘European’ guidelines. This includes a ban on straw-burning on the farm. As I mentioned in a previous blog, burning straw is part of a strategy to control herbicide resistant rye-grass. And where the previous crop has been good, the whole stubble is burnt to enable the passage of the knife point drills.

[By the way, Australians can sell GM-free canola because, unlike the Canadians, they segregate it.]

This isn’t the first time I’ve come across European buyers expecting inappropriate crop management in Australia. A few years ago I spoke at a meeting in the Wimmera, a farming area in Victoria, and was asked a question by an incredulous farmer.

He had been contracted to grow peas by a European company and the crop management guidelines detailed that he should leave some weeds to mature in the crop. The audience fell about laughing, which grew louder when I tried to explain that in the UK it is accepted that arable weeds can contribute to biodiversity. In Australia there is so much land not in production that the pressure to encourage biodiversity on cropped land is far less than in Europe.

Mind you, there are some issues about movement of agricultural produce between Australian states. Western Australia and Victoria, and I think New South Wales, can grow GM Roundup Resistant canola. In between them is South Australia which has declared itself a ‘GM-free’ zone. This means that no GM canola seed or produce can be freighted across South Australia, even by air! I didn’t know it was that dangerous!

British farmers are not the only ones with restrictive rules and regulations. Australia is thinking of introducing downwind pesticide buffer zones for neighbouring crops and native vegetation. It’s proposed that these may be up to around 300 metres! But, surely those trees in the fields must classify as native vegetation? Let’s hope that sense will prevail.

Finally, a little tip...Australian red wines have a great reputation but the 2011 vintage is reputed to be ‘disappointing’. You heard it first here.

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Weeds are a priority

Posted on 09/03/2012 by Jim Orson

I’ve been speaking at series of meetings in South Australia, New South Wales and Victoria, organised by the GRDC, HGCA’s Australian equivalent. However, the GRDC budget is a little higher at A$110 million (about £75 million). The Government provides GRDC with another A$55 million, so the total budget is A$165 million, which represents about half of the total research spend in grains. This means that researchers are very close to practical issues.

The top research priority is weeds. Annual rye-grass (a different species to UK rye-grasses) has developed resistance to nearly all herbicides, including trifluralin and glyphosate. Hence, their arable systems are near to the edge because of this weed.

This year there is a new pre-emergence herbicide from Bayer called Sakura (ai pyroxasulfone) that currently offers reasonable control; unless seedbeds are dry. Weed scientists say that it’s probably only time before resistance develops to its mode of action. One said that Sakura means cherry blossom and you know how long cherry blossom lasts.

Sakura has a new mode of action to Australian grower. It is being tested in Europe, but not by Bayer; the chance of registration in Europe has to be questioned because of its persistence in the soil. Long persistence also provides a greater opportunity for it to move into water.

In many ways, the rye-grass situation in Australia is very similar to black-grass in the UK. There are no longer any real post-emergence options and it is now all about stacking or sequencing pre-emergence or early post-emergence options. Even then control may be incomplete, so cultural control is being adopted.

One option is to grow more competitive crops, but of course too much crop green matter may put yield at risk if there is a ‘dry finish’. The weed is vulnerable in one respect; about 50% of the seed is still on the plant at harvest. Hence, farmers have adapted combines to collect the seed in a towed trolley or put it through a towed seed crusher. Alternatively,  they have adapted combines to leave a narrow swath called a windrow. These are burnt when the fire risk is low, usually in March or April, three to five months after harvest. The narrow swath creates a higher temperature burn to kill the rye-grass seed harvested with the straw.

Post Office - Australian style

Other problem weeds include the wild radish, the same species as our runch, and fleabanes. Herbicide-resistant wild radish is a major issue in Western Australia and fleabane seems to be increasingly an issue in most arable areas in Southern Australia. Again cultural control measures are being adopted. Some wild radish seed can be collected by the combine and it is vulnerable to burning. However...and keep this to yourselves...some farmers are going back to ploughing to control problem weeds after many years of little or no tillage.

Some of the GRDC meetings I spoke at were held in small country towns. These are in crisis, as witnessed by the number of closed shops. The increased productivity of farming has resulted in a dramatic reduction in employed labour and many farmers have given up sheep because of the poor returns from wool. Frequent droughts over the past ten years have cut down the spend in local shops by farmers, with many smaller settlements now down to a couple of inhabited houses, despite the number of post boxes at the local ‘post office’.

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