Keeping wheat crops green as long as possible using fertiliser or fungicide is the key to achieve top yields, according to trials in Britain and high-yielding New Zealand.

The world record wheat yield is currently held by a New Zealand farmer, so crop consultants NIAB TAG has been looking at what can be leant from Antipodean growers.

It found the biggest yield boost came from using high nitrogen together with high SDHI fungicide use in both Britain and New Zealand.

“Anything that keeps the crop green for longer will give you extra yield,” says Bill Clark, commercial technical director at NIAB TAG.

New Zealand growers like later-maturing varieties and also benefit from very high levels of light radiation during the grain-filling stage, which gives them a big advantage over British growers.

This helped Mike Solari, farming near the southern tip of New Zealand’s South Island, grow a world record wheat crop yielding 15.64t/ha in 2010.

Using the British variety Conqueror, Mr Clark says New Zealand trials showed a top yield of 16.95t/ha, while the highest yield in Britain was 11.66t/ha using a high-input programme.

The British high-input regime applied 300kg/ha of nitrogen and four SDHI-sprays, but this year the heatwave in July largely stopped the crop growing and thus limited yield.

Under normal British conditions, wheat crops can add 0.25t/ha per day in yield during the grain-filling stage, and Mr Clark estimates this could be as much as 0.33t/ha in New Zealand conditions.

Mr Clark says with so much of the yield of wheat coming from the grain-filling stage in June and July, prolonging green leaf retention is very important.

He adds SDHI fungicides are more useful than triazoles as they tend to encourage better root growth and prolong greening and so show a yield-boosting effect above disease control.

In New Zealand, the variety Conqueror seem to benefit from later maturity, maintaining green leaf longer than many other varieties, including New Zealand ones.

The trials were part of a collaboration between NIAB TAG in Britain and the Foundation for Arable Research in New Zealand.

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