Effect of high nitrogen rates on wheat yields revealed in…

[Fonte: Farmers Weekly]

Applying nitrogen to Winter Wheat © Tim Scrivener

Increasing nitrogen to a high-yielding feed wheat variety failed to give a response when going above a standard farm practice of applying 220kg/ha.

The work carried out by crop consultant Niab at a site near Warwick on the variety Santiago increased nitrogen fertiliser from 220kg/ha up to 340kg/ha in increments of 30kg/ha.

The highest yield of 11.55t/ha came from the lowest application of 220kg/ha, confirms Richard Overthrow, Niab Tag’s regional agronomist in the west.

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“When we look at all of the nitrogen data we have generated over the years, it is clear that the optimum amount of nitrogen required for most wheat crops in most years is 200-240kg/ha,” he says.

As a result, he sounds a note of caution about using yield prediction to adjust nitrogen amounts, as if something is already limiting yield, adding more nitrogen won’t help.

“We saw a very flat response to nitrogen, with yields actually dropping a bit as the total amount increased,” he adds.

Weather conditions

He says that weather conditions may have had a bearing on the result, and were very different to those encountered in 2015.

“We had a very cold spring in 2016, followed by a lack of sunlight in the summer. So although the extra nitrogen may have helped to produce more grain sites, the crop didn’t have the ability to fill them. The grain specific weight was knocked too,” adds Mr Overthrow.

He will be repeating the work in 2017, using a different variety and a lower seed rate; this season trial was drilled at 320 seeds/sq m, so there was a very thick crop.

“Nitrogen is not a steroid and it can’t be used to raise your long-term yield average. If you haven’t dealt with yield limiting factors, then you won’t see a response and you will simply be wasting fertiliser,” he says.

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