Monday, July 15, 2019

Cold early winter crucial for higher oilseed rape yields

July 2, 2019 by  
Filed under Crops

Oilseed growers are losing up to a quarter of their crop yield each year because of rising temperatures during early winter, say scientists at the John Innes Centre.

Temperatures during a critical period from late November to mid-December are strongly linked to final crop yields – with a mere one-degree rise during this period costing growers £16m in lost income when the crop is harvested the following summer.

The research, which appears in the journal Scientific Reports, is based on analysis of climate and yield data. Temperature variation during this critical time window can lead to harvest losses of up to £160m or 25% of the crop’s total value.

Like many other winter crops, oilseed rape requires a prolonged period of chilling, known as vernalisation, to flower and set seed. Researchers and breeders are focusing on the impact of climate fluctuations on this process as they look to safeguard and stabilise yields.

Chilling of the crop from late November and through December was really important for high yields, said Steven Penfield, a lead author on the paper. Colder weather during January and February didn’t have the same effect, he added.

“Wide variations in oilseed rape yield are a major problem for farmers so we looked at links to temperature to see whether rising temperatures could have an impact on yields. We had observed there was an effect – what is surprising is the magnitude of the effect we found.”

The John Innes team analysed trials data stretching back 25 years. They modelled information from Defra and Agriculture and Horticulture Development Board (AHDB) to see how temperatures were affecting productivity.

“If you ask farmers why they don’t grow more rapeseed, they usually say it’s too unreliable,” said Prof Penfield. “The data in our study clearly shows temperature is having a direct effect on UK agriculture productivity.”

UK improvements in oilseed rape yields in recent years had not been accompanied by increases in yield stability, said Prof Penfield. Year-on-year variation accounted for up to 30% of crop value. Until now the drivers of this instability had been unclear.

Fluctuating temperatures

Winter temperatures are subject to volatility due to a phenomenon known as the North Atlantic oscillation. Fluctuations of atmospheric pressure can bring warmer, wetter westerly winds – or chilly easterlies, which bring colder, drier weather.

In the study the researchers ranked oilseed rape varieties according to the stability of their annual yield. Further genetic analysis showed that the trait of yield stability is not correlated with that of yield.

“This means it should be possible to breed for yield stability and high yields together without having to sacrifice one for the other,” said Prof Penfield.

The study, in establishing a clear link between temperature and productivity, raises the hope that future rapeseed crops can be bred so that they are less temperature-sensitive, offering breeders the prospect of more stable and productive yields.

studiopress

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