N return boost from strobilurin use

According to a new study by ADAS, which was conducted at ADAS Terrington in Norfolk, it can also boost the return on investment from nitrogen use.

The study, compared the effects of using a base fungicide strategy of 0.75 l/ha of epoxiconazole (Opus) + 1.0 l/ha of Bravo (chlorothalonil), with a three-pronged strategy of this same mixture, including the addition of 1.0 l/ha of Amistar (azoxystrobin).

Fungicides were applied at GS32 and GS 55 across six different nitrogen doses ranging from zero to 330 kg/ha.

At all nitrogen doses of 200 kg/ha and above the inclusion of azoxystrobin was found to add at least 0.4 t/ha to yield for the same nitrogen dose.

At 200 kg/ha (82kg/acre) of nitrogen, while epoxiconazole + Bravo yielded 10.99 t/ha (4.45t/acre), yield was increased by 0.6 t/ha (0.25t/acre) to 11.6 t/ha (4.69t/acre) where Amistar was also used.

Optimum

Additionally, the economic optimum nitrogen rate was increased from 210 kg/ha (85kg/acre) to 219 kg/ha (88kg/acre) with Amistar inclusion, with margin over nitrogen cost at these doses also increased by £47/ha (£19/acre) - from £994 to £1041/ha (£402 to £421/acre) - where the Amistar + Bravo + epoxiconazole treatment was used.

According to study co-ordinator, Dr Sarah Clarke of ADAS, while visible disease control may explain much of these improvements, sub-clinical effects may also contribute, and results have practical benefits for growers.

“You can put the same amount of nitrogen on and get increased yield, or, the other way of looking at it, you can apply more nitrogen and get even higher yield.

“In short, you can justify increasing your nitrogen use with an increasing fungicide programme and still increase your margin, even though your costs are going up.”

According to Dr Clarke, while theoretically the results also suggest growers can target the same yield using less nitrogen, higher margins were achieved at higher nitrogen doses.

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