Reduce risk with better-informed wheat variety selection

Expansion and better use of Recommended List (RL) data will soon be helping growers to make better-informed wheat variety choices and expose their businesses to less risk.

A number of factors are threatening crop production in the UK, most notably increasing extremes in weather associated with climate change and the potential loss of fungicides through regulation or resistance.

The first problem could result in more widespread and higher disease pressure in crops. The second leaves growers with little means of controlling yield-depleting diseases such as septoria in wheat.

Then there are market pressures.

End-users largely dictate the varieties growers put in their drills each autumn, but the varieties may provide little benefit on-farm apart from a more certain market – leaving all the risk with the producer.

See also: Find your farm’s 2016 money-making cereal and OSR variety

Simon Oxley, senior research manager at AHDB cereals and oilseeds, believes growers should consider these agronomic and market risks more carefully when making variety choices in future seasons.

“There is that mindset on farm of ‘If I grow a variety and grow it well, why change?’ Which is particularly the case with feed wheat.

“We have to be smarter than just growing a variety because it does well.

“We need to identify why varieties do well, which will help us identify what to look for in new varieties and give growers the confidence to change,” he added.

Dirty varieties

A perfect example is the popular Santiago, which has high treated yields, but requires careful disease management with fungicides.

However, it has a long way to fall if things go wrong, with an untreated yield of just 75% of the mean, so comes with significant risk.

Trying to find out why it does so well on-farm and look for those traits in other varieties coming through the system, but with higher disease resistance ratings, would offer equal or better output with less risk for the grower.

“There are [wheat] varieties coming through with better resistance, so there are potential gains to be had.

“We could lose fungicides, so we have to think about how we can manage disease in a different way, using the information we have, so we need to help growers try new varieties sooner than they normally would,” explained Dr Oxley.

Relative risk

Dr Oxley acknowledges the RL’s limitations and the AHDB is working hard to improve how it assists growers in variety selection.

One area he is keen to develop further is recommending varieties on “relative risk”, which has been tested in feed winter wheat this year.

Risk comparisonThe system plots “agronomic merit” against untreated yields (see right) and puts varieties in relatively high, low or neutral risk positions compared with established ones and it is hoped it will encourage growers to select from the top right quarter.

It is calculated by giving the current RL agronomic scores weighting. For example, septoria is the most important disease, so has the highest rating of 4.

Lodging resistance is also a high 4, while yellow and brown rusts have a 3 and the less-important Septoria nodorum isn’t weighted at all.

The resistance scores are then multiplied by weighting and combine to give a cumulative score or agronomic merit.

“If a variety has a 7 for septoria, it is already likely to be on the right side of the table, but it might have a low untreated yield due to other weaknesses, so it would be risk neutral,” explained Dr Oxley.

Better the devil you know?

In feed wheats, Santiago sits in the bottom left and provides high risk if things go wrong, but will continue to be popular while fungicides continue to give adequate control of disease.

However, two additions to this year’s RL for 2016-17, Siskin and Graham – both with septoria scores of 7 – offer growers risk-averse choices, but many have no experience of growing them.

“Based on previous data, they have an overall better agronomic package and if left untreated have a relatively high untreated yield.

“The question is, are you going to stick with the devil you know or jump to something that potentially has less risk, but you have little experience of,” said Dr Oxley.

Challenge

While resistant varieties with high, untreated yields sound appealing, disease virulence is ever evolving and can change through a season.

Yellow rust in wheat had a recent change in population, with the aggressive Warrior race overcoming the resistance of some varieties, seeing their resistance scores slide.

“Although we are getting good varieties coming through with good disease resistance, things can quickly change, so in-season crop monitoring remains crucial.

“At present it is up to the grower and agronomist, as the national monitoring we do is not sufficiently local enough. We need to be able to warn growers when to look in the field in real time,” said Dr Oxley.

It is this step towards an integrated approach to disease control that is tricky, with a cheap T0 to protect crops against yellow rust an easy option, allowing the agronomist to sleep at night.

“On a susceptible variety it is the right thing to do, but would you do the same on a resistant one? It is all about perception of risk and how much you are willing to take,” he added.

Consistent quality

On top of disease management, achieving a consistent quality for the desired market is also a big consideration in variety selection to avoid losses when it comes to selling the crop.

RL trials are have recently been extended throughout the UK to test certain varieties in extreme conditions they would not normally be exposed to.

For example, group 1 milling wheats are tested up in Scotland and down in the South West, two areas that are away from the traditional milling wheat markets.

Building data on how they perform in different conditions can give a grower and end-user confidence they can perform consistently if a freak season occurs in other regions.

“Also, there are higher-yielding milling wheats coming through and there is a worry that protein content will be lower, but are we using the right measure?” said Dr Oxley.

The protein content of grain is complex and not all of it is functional in making the final product, such as bread or pizza dough – which both require different characteristics.

By picking the protein content of milling varieties apart, it is hoped that grain with less than the 12.5-13% standard might still gain top premiums because they contain more functional protein.

“Consistent protein over a number of years and seasons is the name of the game, but we need more measurements of what makes a milling wheat,” added Dr Oxley.


Simon Oxley was speaking at the recent AHDB Agronomists’ Conference at the Peterborough Arena, which focused on helping agronomists and their clients better manage agronomic risk.