Variable nitrogen application on Berkshire farm improves yields

Oxon grower and Farmers Weekly farm manager of the year finalist Simon Beddows is carrying out his own trials to see if precision farming pays. Tom Allen-Stevens gathers the results.

Simon Beddows is naturally inquisitive. It’s not that he doesn’t trust commercial trials data. He’d just much rather find out the truth for himself.

“You can make statistics show whatever you want. But if you’re in charge of your own you get a much clearer picture,” he says. “And every farm is different – what works on one might not on another.”

That’s why, since he took over as manager of Phillimore Farms on the Berkshire/Oxfordshire border seven years ago, he’s been running his own trials to test various agronomic criteria. “The secret is to study one or two things at a time and do them well.” Over the years this has ranged from testing glyphosate to fungicides. Currently the focus is on fertiliser and whether precision application pays.

The 1000ha estate, between the Chilterns and the Downs, lies on poor soils that vary from gravel to clay cap. With high yields out of the question, the farm aims for quality and usually meets milling spec with its Solstice and Cordiale winter wheats. “It’s actually relatively easy, as you rarely dilute the protein. The rest is down to attention to detail.”

BASIS and FACTS-trained, Mr Beddows does his own agronomy. In 2006 he brought in SOYL to precision-sample part of the farm for phosphate and potash and provide him with variable-rate application maps. Impressed with the results, he got the company to map the remainder of the farm and then moved to SOYLsense, its variable-rate nitrogen service, in 2007.

“But I wanted to do it properly and I needed to justify the cost – prove that it works,” he says. So he introduced a trial into two fields – one of feed wheat and the other milling. In each, field nitrogen was blanket-applied to one half and applied according to SOYL’s variable-rate application maps on the other half. One-hectare blocks from each side were harvested and put over a weighbridge.

“I was sceptical there’d be a difference – you couldn’t spot it from the maps SOYL supplied.” But the variable rate brought him just under 0.5t/ha higher yield – about 5%. So he decided to repeat the trial for another two years to ensure the result was consistent.

Problems with producing the maps in 2008 in cloudy conditions meant the trials were scrapped but, in 2009, fields of Solstice and Robigus were trialled. Otherwise the parameters were the same – each field received a blanket application of nitrogen with sulphur in early March, with the following two doses in late April and mid-May spread evenly on one half and variably across the other of each field (see table).

“The variations weren’t huge – the tractor driver wasn’t actually sure the rate was changing at all. “For 136kgN/ha applied on the first split, for example, the rate varied from 117 to 156kgN/ha. “But it felt good when I was going through with the combine, so I knew we’d get a result.”

Again the Solstice gave a 0.45t/ha yield benefit – about five times the extra yield needed to pay for the service. But he got double the benefit from the Robigus, with a yield boost just shy of 1t/ha. “It looks like it really does work – the figures can’t lie.”

Mr Beddows aims to run the same trial in 2010, with a field of Viscount in place of the Robigus. “I’m hoping for a damper spring – in both years so far it’s been dry, which has limited the potential of the crop.”

The service, too, is set to improve, with two extra high-resolution satellites launched in time for the 2010 growing season that will increase the provision of maps. “There used to be a gap of up to a fortnight between your target date for maps and when they were actually taken. It’s now much quicker – usually just two days – and they’ve put on more dedicated staff, which really helps.”

SOYL provides a self-service web-based portal for those who wish to generate their own application maps, although Mr Beddows prefers these to be done for him. But, despite good results, he’s keeping an open mind as to whether he will stick with the service.

“It’s got to prove itself in year three. But whatever happens, precision application has to be the way to go. The inputs we use won’t last for ever – if we need to produce more and reduce our carbon footprint we’ve got to be cleverer with how we use our finite resources.”

Phillimore Farms precision trials – 2009 results     
All figures per ha Solstice Robigus
N applied (avg over field):
2 Mar 09  23:0:0:45 132kg 132 
23 Apr 09 34.5:0:0 380kg 260
15 May 09 34.5:0:0 180kg  170
Blanket-applied plot  10.15t  11.78t
SOYLsense plot  10.6t   12.76t
SOYLsense benefit  +0.45t  +0.98t
   +4.4%  +8.3%
Breakeven yield benefit req’d*  +0.9%  +0.8%
*Based on service cost of £3/ha + 2 maps generated @ £1.50/ha = £6/ha and net margin of £656/ha (Solstice) and £691/ha (Robigus)    

SOYLsense summary 

What is it? A service that uses satellite infra-red images to give a picture of crop canopy, created at defined growth stages. On-going calibration on the ground, included as part of the service, relates the maps accurately to Leaf Area Index (LAI). Using this and HGCA winter wheat canopy management guidelines, variable-rate nitrogen recommendations are generated.

How are rates varied? On the first application more is applied to thin areas to help them catch up and less to thicker crop to avoid lodging. On the second split there is the option to switch to feeding more to the thicker areas to encourage the crop to reach its potential.

How does it compare with a tractor-mounted sensor?

Plus points:

  • Gives you a picture of the whole field, not just the area near the tractor

  • Paid for on a per ha basis, so more flexible and cost-effective

    Potential downsides:

  • Maps are historic, not real-time, and lower resolution

  • Continued cloud cover can limit service

    How much does it cost?

    The SOYLsense service starts at £4/ha for one image and related application maps up to a maximum per client business of £3,500. For more information go to or call 01635 204190.

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