NIAB - National Institute of Agricultural Botany

Orson's Oracle

Disappointing rape yields; causes?

Posted on 19/08/2016 by Jim Orson

Ladies of a certain age could not stop talking about scything following the most recent series of Poldark. I took this as great news, assuming that they were interested in the traditions of agriculture. In order to reinforce their new found enthusiasm, I offered to show them the proper technique for scything. This was because the actor in Poldark (Aidan Turner) appeared to be lunging at the grass rather than cutting it, something that was recently highlighted in the Sunday Times. My offer was met with a total lack of interest and mutterings about scything topless. A further offer to scythe bare-chested was met with near revulsion. It then clicked, it was not the scything but the bare-chested Aidan Turner: an example of jumping to a false conclusion by not taking into account the whole picture.

It is currently estimated that average winter oilseed rape yields in south Yorkshire and further south are down by around 10% this year. It may be that, like winter barley, the average yields will increase when the results of the harvest further north are taken into account. The question is what has caused this disappointing yield. Obviously the ravages of Cabbage Stem Flea Beetle reduced yields in some areas but yields also seem disappointing in crops unaffected by this pest.

There was talk a few years ago that oilseed rape yields were very dependent on good rainfall in June. This was based on a graph that appeared in the introduction to HGCA (now AHDB) project report 402. This graphed the field yields at Boxworth near Cambridge and June rainfall.

The project quite rightly argued that oilseed rape yields are very dependent on conditions during grain fill because, unlike wheat, final rape yields depend little on reserves in the plant. Moisture availability is, of course a major factor. However, it has to be pointed out that in wet weather there are lower levels of solar radiation, thereby reducing photosynthetic activity and also that correlation does not necessarily mean causation.

This year, despite good supplies of rain in June in most of England, yields are below average and so is the graph above the researcher’s Poldark moment? Maybe other factors were at play to cause annual variations in field yields and the fitting of one line through field yields on one farm was not indicating the right conclusion. This appears to be reinforced by the terrible yields in 2012 when there was no shortage of rain in June.

In HGCA project report 502 a different conclusion was drawn on the influence of the weather on oilseed rape yields. It identified autumn conditions that could possibly lead to the development of an effective canopy and the establishment and retention of a good root system. In addition, similar to analyses in wheat (see blog posted on 8 July), it suggested that good levels of sunshine and low rainfall in April contributed towards higher UK yields. No association between June rainfall and rape yields was identified.

In this case, the researchers suggested that sunny and warm conditions in April resulted in good levels of photosynthesis and pollination. In contrast, March and April this year were cold, which delaying flowering, and also rainfall was generally above average. However, there may be other factors involved. The years 2011 and 2015 were good years for rape yields and both had very dry springs. This would have enabled good spring root growth, unimpaired by even temporary waterlogging. Hence, nutrient efficiency and the ability to explore the soil profile for water were improved. Therefore, perhaps the ability to access water during pod fill is the key rather than rain in June at a time when the level of photosynthesis is critically important. This is, in fact, the conclusion of the actual field research done in HGCA (AHDB) project 402.

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Tramline thinking

Posted on 08/08/2016 by Jim Orson

Many farmers voted for Brexit in order to reduce unnecessary red tape and legislation that they consider harmful to their businesses. However, it is hard to believe that the current environmental standards they are called on to achieve will be relaxed. For instance, the EU drinking water directive has an unscientifically set very low maximum for pesticide content in drinking water at the tap. Will Brexit change this? I really doubt it. Despite the difficulty this directive causes, it is only right that consumers have confidence in the water they drink. Relaxing the standard would be a hard sell.

Around the turn of the millennium, I was involved in an EU research project that aimed to reduce soil erosion on a landscape scale. It was led by the Burgermeister of a small German town who was fed up with the underground car parks filling up with silt after a heavy rain. One of the main findings was that around 80% of the water running off the surface of the cultivated area of fields was from tramlines; in that water were pesticides and nutrients. This came as a profound shock to me and to the farmers at the meetings at which the results were presented.

TramlineThis result, along with other projects, initiated efforts by the Voluntary Initiative and by pesticide manufacturers to reduce surface run-off from the cultivated field via tramlines. Many of the advised mitigation measures are common sense but the pressure remains to reduce further the pesticide levels in surface waters.

HGCA (now AHDB) funded a large project on establishing tramlines. The report concludes that “….. it is predominantly the substantial soil compaction which may be caused during the autumn spraying operation (mediated by soil conditions at that time) which is primarily responsible for the risk of run-off and diffuse pollution over winter months; rather than the lack of good ground cover from emerging vegetation”.

The details in the report of the conditions at the time of the use of tramlines are scant. I think the tramlines were established shortly after sowing winter wheat and there was only one pass in the replicated experiments. As the short summary of results I have quoted implies, sown tramlines were investigated. They appeared to be more successful in reducing run-off when very low tyre pressures were adopted but overall their impact was disappointing when tramlines were first used at, I think, crop pre-emergence or very early post-emergence. The results may have been different if the sown tramlines were first adopted at a later crop growth stage. However, sown tramlines come with the problem at harvest of later maturing plants.

Another conclusion is that using a self-propelled rotary harrow behind the rear tyres of the spray vehicle will reduce water flow along the tramlines. This is entirely logical but of course such a cultivator may not be as effective where there are multiple passes along the tramlines under wet conditions during the autumn/winter.

The project also modelled the impact of improved tramline management on a landscape scale. It came to the same conclusion as we did all those years ago in our EU project. Identifying high risk fields for water run-off is crucial. Getting it right in these fields has a disproportional benefit for the whole catchment. It is crucially important that each farm makes a real effort to identify high risk fields.

Getting it right, particularly in high risk fields, includes minimising the number of passes along the tramlines during the autumn/winter through crop choice/rotation as well as minimising soil compaction in the tramlines; this involves both the timing of the spraying operation and careful choice of tyres and tyre pressures on the spray vehicle. There is additional information on these issues on the Voluntary Initiative website and through the WaterAware App.

Improving water infiltration rates in the whole field is also important. One obvious way of achieving this is to use soil amendments regularly. However, most organic manures contain levels of nutrients which may increase the risk posed by nitrate and phosphate levels in the water lost from the field. Research work carried out by NIAB TAG, in a project funded by The Morley Agricultural Foundation, shows that green waste compost, which contains relatively low levels of nutrients, can substantially improve infiltration rates for a few years after application.

In addition, there needs to be a commonsense approach to the placement of tramlines. For instance, entering a field at the top of the slope is important because it prevents water running down the outside tramlines having a direct route out of the field. Naturally, establishing a grass based strip alongside any water course at the bottom of the field will reduce surface run-off. This strip has to be complete and will be more effective if there is a tramline, not connected to other tramlines, running in the parallel direction.

Tramline management is an important issue where Controlled Traffic is adopted and becomes an even greater challenge in fields where the risk of surface water run-off is already high. Great care needs to be taken on the layout of tramlines as well as their day-to-day management because minimising compaction can have a particular environmental premium.

So the message is that it comes down to common sense. Thankfully, farmers are usually extremely good at observing what is going on in their fields and using common sense measures to reduce problems.

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Brexit exposes lack of agricultural knowledge

Posted on 22/07/2016 by Jim Orson

I usually read the opinion columns in The Times. They are generally thoughtful and at times provocative. However, I was dismayed by the lack of understanding of agriculture shown in a piece by Emma Duncan on 9th July. She is an assistant editor of The Economist and so, in my view, should be more aware of how the economics of the industry ticks.

She was a Remainer and starts the article by saying that she has been looking for some good news from Brexit. She says that she has found solace that Brexit is likely to be bad news for ‘greedy farmers’. It appears from the article that she has complete disdain for the industry.

Her conclusion is that after Brexit there will be less support for agriculture leading to lower food prices, less intensive systems and land going out of production, so there will be more land available for building houses.Brexit Farmers

She is clearly thinking that we are receiving price support rather than support for eligible land area. Price support generally disappeared a couple of decades ago, although the sugar price is supported for another year or two. Hence, we are already competing in world markets and so removing current support measures will not reduce the product prices received by UK farmers.

As for making more land available for building houses, landowners already jump at the opportunity to get building permission. We do not have to see land going idle before they are willing to sell!

What really concerns me about this article is that an opinion-former is unaware of the real issues of food production in the UK. This does not bode well for public support for any agricultural subsidy arrangements post-Brexit.

To add to my concerns, Andrea Leadsom, the new Defra secretary, also seemed at one time to be unaware of the market issues relating to agricultural products. She has been quoted as a supporter of “reducing burdensome EU red-tape, saving farmers time and making food cheaper” and in 2007 argued that farming subsidies must be abolished.

I realise that there is a real hope that red tape can be reduced, but I think much will have to continue to reassure our customers that we have a transparent and traceable food chain.

Brexit may mean a return to more scientifically based decision-making, particularly for pesticides. Interestingly, there is concern expressed by some in the wider EU that decision-making will suffer because of less input from British scientists.

The future may possibly hold some advantages from Brexit but there is a huge challenge ahead to inform decision-makers, opinion-formers and the general public of the true context and importance of food production in the UK. Judging by the article in The Times, there is a long way to go.

Pesticide Regulations post-Brexit is a major theme of The BCPC Congress at Brighton in early October.

Blog 175

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English wheat harvest 2016

Posted on 08/07/2016 by Jim Orson

I have just attended the funeral of a former colleague. One reading included the following words: “There is no longer any room for pretence. At harvest time the essence is revealed – the straw and chaff are set aside, they have done their job. The grain alone matters – sacks of pure gold.” Sacks of pure gold may be an exaggeration with today’s market prices.

What will the English wheat harvest of 2016 reveal? Over the last few years I have written a blog in early July, half way through grain fill, trying to predict yields. As usual, I have not really got sufficient meteorological data to attempt a complete scientific analysis. Nevertheless, here goes.

wheat harvestThere have been studies to try to associate historical wheat yields with weather conditions. The most notable was published in 2000. This states that the most influential weather impacts on the yields of well grown wheat crops are (1) negative effects of rainfall before and during anthesis (early June), during grain-filling and in the spring (2) winter frost damage (3) a positive effect of the temperature-driven duration of grain-filling and (4) a positive effect of radiation around anthesis, probably due to increased photosynthesis.

Naturally, there may be an interaction between rainfall and solar radiation. Radiation levels are low in wet weather. This might help to explain some of the dominance of rainfall distribution in this analysis.

The importance of lack of rainfall at key times is highlighted. “Negative effects of rainfall during the estimated early-reproductive phase, the estimated anthesis phase, the estimated grain-filling phase and the February/March period are the most dominant effects in the climate response sub-model (explaining 54% of the grain yield variation accounted for by the model).”

This strikes a chord with my experience. High wheat yields seem to be associated with dry but not drought years e.g. 1984, 2014, 2015. May rainfall explained much of the yield variation throughout the country last year. Where there was little rain in May, drought conditions limited the potentially very high yields.

In 2014 and 2015, we had dry conditions from mid-February/March, April and June, the stages highlighted by this paper. In addition, we had a long grain fill because of coolish conditions both day and night (Number 3 in the paper summary above) and good levels of radiation around anthesis (Number 4 in the paper summary above).

For much of the country, this year’s weather does not appear to point to high yields in 2016. February had average or lower than average rainfall and March was dry in the North East but the rest of England had a wetter March than average. We had plenty of rain in June in much of the country but again the North East had average rainfall. Radiation levels were generally around average for much of the spring but, critically, lower than average in June, except in the North of England, which enjoyed average or above average sunshine and radiation. June temperatures were higher than average except close to the East Coast where the cold North Sea temperatures resulted in average temperatures in the coastal strip from North Norfolk northwards.

Therefore wheat yields are likely to be around average, perhaps on the disappointing side of average in the central and southern areas that have had particularly low levels of radiation and well above average rainfall for June. The exception might be the very North of England where I suspect that there will be above average yields but perhaps not at the levels achieved last year, providing, of course, that the harvest weather is good.

The paper I quoted earlier in this blog probably reinforces rather than forms my somewhat instinctive conclusions. As usual, I hope yields will be better than I predict!

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Black-grass votes to remain

Posted on 24/06/2016 by Jim Orson

We may have voted to leave the EU but black-grass has decided to remain. It is hard to generalise but for many, particularly those who have yet to grasp fully the enormity of the problem, there has been a backward step this year in its control in winter wheat. Some farmers still have a rather touching faith in what herbicides can achieve.

In many situations the pre-em/early post-em herbicides gave good control of black-grass plants in the autumn. However, the survivors grew strongly in the warm autumn/winter conditions and established more black-grasstillers than perhaps could reasonably be expected. In addition, in some areas wet soil conditions meant that crop competition was disappointing, particularly in the poorer drained parts of fields.

There are instances where just a couple of weeks delay in drilling has had a remarkable effect on black-grass populations. The critical period in many areas was when drilling had been delayed from the beginning of October to mid-October. Soils were moist and obviously there was a high emergence of black-grass during that period. Crops drilled in the middle of the month rapidly established and provided good crop competition. The later drilling would also have helped the efficacy of the herbicides.

Conditions for the spring establishment of cereals were not as favourable as in the previous four years, particularly on the really heavy soils. This resulted in later drilling dates, which may theoretically have been advantageous in terms of black-grass control. Despite the later drilling dates, there was often sufficient moisture for the soil residual grass weed herbicides. Hence, herbicide use in spring barley provided good reductions in black-grass numbers where there was good crop competition. The issue in spring wheat was the restricted herbicide options for black-grass control. This, I hope, will be rectified in the coming seasons.

Personally, I am not in favour of delaying spring drilling of cereals in order to take full advantage of black-grass emergence prior to drilling. In my opinion, it is far better to drill as soon as conditions allow in order to maximise the possibility of soils being moist for the residual herbicides and to help ensure that the spring cereal is competitive. In addition, residuals are more likely to be ‘hot’ in the warmer conditions that tend to prevail later in the spring.

For the first time in three years I am not aware of any instances of exceptional numbers of black-grass emerging in spring drilled crops. It tends to confirm my suspicion that this phenomenon was due to the cold and wet summer of 2012 resulting in ‘super-dormant’ seed being set. It seems that it has taken three seasons to clear the back-log. In parts of Eastern England the last few weeks have been cold and wet. Hopefully it will turn warmer in the near future to ensure that we do not go through the same experience again.

So what has another season’s experience taught us? I think it has confirmed that many farmers and advisers need to assess more carefully the threat of black-grass to next year’s autumn sown crops. There is no point in taking an unrealistic view of what herbicides can achieve. In many instances the background population of black-grass needs to be reduced to a level where herbicides can prevent yield loss and also provide the best chance of limiting seed returning to the soil. This means that there should be the potential of no more than 10 black-grass plants/m² (at a push 15/m²) emerging in an untreated winter cereal crop. Such numbers do not occur in an autumn sown cereal where there is so much black-grass emergence between the previous and the current crop that at least two applications of glyphosate are required in order to prevent emerged black-grass plants reducing further emergence through competition (no, it is not allelopathy). In such situations, winter or spring drilling are the only options.

All farmers and advisers are aware of the cultural options available and attention to detail is essential, such as estimating where in the soil profile the majority of the viable black-grass seed lies. This should help to guide the choice of type and depth of cultivation required. All approaches should be considered, including hand and chemical roguing.

I constantly witness the value of the strategic use of the plough. Now, please do not get back to me and say that ploughing would ruin the soil after many years of adoption of non-plough tillage. I have never seen any trials or field evidence to support such a statement. All options have to be considered!

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