Tuesday, January 21, 2020

‘Don’t leave oilseed rape performance to chance’

December 23, 2019 by  
Filed under Crops

A well-structured crop canopy which results in a high number of seeds is the biggest single determinant of performance success with oilseed rape, suggests research.

The number of seeds produced accounted for two-thirds of the 4.8t/ha yield variation recorded between 150-plus crops involved in the first three years of the Oilseed Yield Enhancement Network competition, according to an ADAS analysis.

“To have a chance of getting 5t/ha you need more than 100,000 seeds/m2,” said ADAS head of crop physiology Pete Berry, who spoke to growers at the Dekalb Oilseed Rape Hub, held at last autumn’s Croptec event.

“Since seed number is determined by the amount of light intercepted in the 2-3 weeks after flowering, in our experience this means a well-structured canopy with a green area index (GAI) of between 3.0 and 4.0.

Room for improvement

Most oilseed rape crops are capable of yielding around 9t/ha. But most leading farms and research trials for oilseed rape seldom achieve this. The average commercial farm produces even less – around 3t/ha – with little increase in over 10 years.

The highest yielding 25% YEN crops also came from growers who used noticeably lower than average seed rates but more fungicide applications, Dr Berry told growers at the East of England Showground, Peterborough.

“We’ve seen a clear and consistent association between yield and the number of days from flowering to desiccation too. On average, an extra 11 days of seed setting and pod filling has accompanied a yield difference of more than a tonne/ha.

Seasonal factors

“On the nutritional side, both soil and post-harvest seed analysis has highlighted a relationship between the highest yields and higher than normal magnesium contents which we are investigating further to establish the extent to which this link could be causal.”

The vagaries of the season also have an important influence on OSR performance. Long-term ADAS studies show that a dry December, warm March, dry and sunny April and cool, wet May are all associated with the highest yields.

But Dr Berry stressed that weather factors only account for less than 40% of the variation recorded in annual crop yields. This leaves more than 60% of the variation associated with farms and farming factors – many of which can be controlled.

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