Lodging is costing the UK oilseed rape industry up to £137m a year, according to a “first of its kind” aerial field survey, suggesting that growers are underestimating their losses from the problem.

The BASF-funded survey, carried out by ADAS, used aerial photographs to get a handle on the size of area affected and the severity of damage caused. One of the key findings showed on average 35% of the oilseed rape cropping area lodged.

Senior research consultant at ADAS, Peter Berry, believes the results highlight the need to take the threat of lodging seriously and he urges growers to work hard to prevent lodging in their crops.

“The impact on oilseed rape crops can be substantial and will need to be addressed this year to prevent further losses.”

The survey showed more than 99% of fields had some sort of lodging, highlighting the scale of the problem and how much we underestimate it,” he says.

Last year saw exceptional levels of lodging across the country. However, due to the nature of the problem, growers have found it difficult to assess how much has occurred in fields and the degree of damage it caused.

This has changed with the new research and Dr Berry is feels it is a big step in helping to address the problem.

“Growers are going to have to be really on the ball with their management of OSR and take a zero-tolerance approach to lodging.”

“This year’s oilseed rape crops are generally smaller with poor rooting systems and weaker stems. This could lead to an increased risk of lodging due to a rapid growth in the spring, putting pressure on rooting.”

Yield loss from lodging is a consequence of a reduction in photosynthesis from reduced light penetration and subsequent low seed set and poor seed. It also affects the arrangement of the pods, resulting in increased pod shatter.

“The survey showed how lodging interferes with crop management and harvest as well as light penetration, which has adverse impacts on the yield,” he notes.

Findings

Carried out in 2012, the survey showed that on average, 35% of oilseed rape cropping area lodged. This was often in the centre of the field, making it harder for farmers to appreciate the true level of lodging.

If the average lodged area of 35% is representative of the whole country, it is estimated that lodging could have reduced the national average yield by between 0.25t/ha and 0.61t/ha (based on a projected national yield of 3.5t/ha in 2012).

This would result in losses of between £88/ha and £214/ha. Growers can ill afford these kinds of losses and so in a year when many oilseed rape crops are already suffering, reducing the lodging risk is seen as an ideal way to get on the front foot.

The estimated national cost of lodging in oilseed rape amounts to £85m, ranging from £60m-137m per farm. This figure outlined in the survey works on a basis of an average yield loss figure of 0.38t/ha. Dr Berry notes that early lodging may push this estimate even higher.

Most lodging was found in the main part of the field with levels of lodging generally reduced within the overlaps between the field margin and field centres.

“This is a contrast to what is observed in cereals, whereby lodging is frequently observed in the overlaps between the field margin and field centre,” he highlights.

Despite the findings showing some alarming losses, experts are confident the problem can be dealt with.

ADAS research scientist Sarah Kendall noted findings revealed that neighbouring fields were seen to show very large differences in lodging, confirming the ability to mitigate risks in the presence of poor water.

The sheer damage that lodging can cause in a field is highlighted by the survey, which shows levels of up to 90% could cause possible yield losses of up to 1.6t/ha.

Rectifying the problem

BASF agronomy manager Clare Tucker advises that assessment of Green Area Index (GAI) should be routine for all crops every year if lodging risk is to be reduced and yield to be maximised.

“It will be essential in gauging when and where metconazole should be applied,” says Mrs Tucker.

This year’s crops are generally smaller with poorer rooting systems and weaker stems. Once growth starts in the spring, this could put pressure on rooting and the risk of lodging could be high.

There are a number of options available in order to measure the GAI of a crop including BASF’s iPhone app, OSR GAI, available to download from its site.

Growers and advisers will need to use the GAI tool starting in March and if the GAI of the crop is greater than 0.8, then an application of up to 0.8 litres/ha of metconazole (Sunorg Pro) to the crop will be economically justified. This should be done once the crop is “visibly” growing, from about mid-stem extension through to yellow bud.

The mid-stem extension metconazole applications in March will shorten the crop and reduce the risk of lodging the most. However, strong active growth is more important than actual growth stage so it is better to delay if too cold or dry.

“Applying a PGR below a GAI of 0.8 can have a negative effect on yield, since canopy development is less than the optimum.

“However, it’s important to note that even if the crop has a GAI of more than 2.0 at stem extension, we would advise growers not to apply a PGR if dry or cold weather has stopped growth. Strong, active growth is more important in terms of applying a PGR rather than growth stage, so a later application timing at the yellow-bud stage may be more appropriate in those circumstances,

“There will be a lot less nitrogen in the soil this year. We’ll probably see earlier applications of nitrogen due to a lot of the crops being smaller. An application of 40-50kg at the end of February followed up with two more,” she says.

The GAI tool should also be used right into April at about yellow bud. At this stage metconazole will help maximise canopy effects and seeds/sq m for yield. It will also reduce lodging risk and contribute to sclerotinia control.

The April application has been the most common in recent years, in part due to the need to wait for sustained active growing conditions before application.