Climate change may boost rapeseed yields

A study in the United Kingdom finds a connection between warmer weather in October and higher yields of oilseed rapeseed

As much as climate change poses many challenges for farming in the coming years, one study out of the United Kingdom has shown an unexpected climate plus for oilseed rapeseed.

The study by the John Innes Centre in Norwich investigated a link between warmer weather in October and higher yields of oilseed rape, the second largest crop in the U.K. According to the report, the crop, which is planted in the fall and harvested the following summer, is particularly sensitive to temperatures at certain times of the year,and that response is reflected in annual yields, which can vary by as much as 30 percent.

Researchers were previously aware that warmer temperatures in October resulted in higher yields the following summer but the reason has been unclear.

“Mainly we could see that U.K. yields were very variable between years,” said Steven Penfield, one of the study’s authors. “We thought that if normal weather variation could have such a dramatic effect on yields, then we would need to know the underlying basis if we want to think about the likely effects of climate change. So, the problem was clearly important. This is aggregated on a landscape scale. The value of this variation to the U.K. economy is around £200 million (C$341 million). Not all of this is caused by temperature variation. There will also be effects of rainfall and sunshine hour variation.”

The study showed that the temperature in October was important because it set the point at which the plant went through the transition from the vegetative state to flowering when, traditionally, the mean temperature would be between 10 and 12 C. However, the warmer Octobers actually led to a delay of the flowering stage, which resulted in the higher yields.

In the study, the team used soil surface warming cables to raise the temperature of field plots by between 4 C and 8 C, simulating the warmer October temperatures. The plots were six sq. metres and the two varieties of oilseed rape used were cabriolet and slapska slapy.

“They were selected because they are both winter oilseed rape, but they have different cold requirements for flowering,” said Penfield.

Winter oilseed rape is grown in northern Europe and parts of the U.K., where it is seeded in late August and harvested the following July.

In Canada, canola has replaced traditional rapeseed, just as oilseed rape has replaced most conventional rapeseed in Europe.

The trials by the JIC research team were the first time the warming technique has been used on a crop in the field.

“It’s important to be able to do this because yield is highly weather dependent in oilseed rape and it is very likely that climate change will have big consequences for the way we can use crops and the type of variety that we need to deploy,” said Penfield.

The difference in growth prior to flowering was observable.

“(It was) very noticeable,” said Penfield. “Plants that come from warmer autumns remain much leafier, even into flowering. We used heated cables which lie on the soil surface. These reached a temperature of around 30 C and help warm the plants.”

Temperature is critical for the oilseed rape lifecycle because it controls at what point the plant starts its transition from the vegetation growth stage to flowering. The lab tests on dissected plants showed that the warming conditions in October delayed floral transition by between three and four weeks for both varieties, and the genetic tests showed that the genes associated with vernalization in cold conditions were also highly expressed in the warmer temperatures.

“The key question is whether higher temperatures cause good yields, or (is it the) absence of low temperatures,” he said. “Our view is that only the latter makes sense. Low temperatures make for premature fulfilment of the vernalization requirement, which leads to the end of growth before the plant has reached maximum potential. What we see is because of the climate change that has already taken place, the last cold Octobers being more than 20 years ago.”

According to JIC’s news release, the good news for oilseed rape farmers is that data from the Met Office, the U.K.’s national weather service, shows cold Octobers are much less frequent than they have been in the past.

The study was recently published in the journal Current Biology.

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