Field N tests leave considerable doubts

18 July 1997




Field N tests leave considerable doubts

SOIL mineral nitrogen testing has attracted scepticism at Heath Farm, North Rauceby, Sleaford, Lincs.

As winner of the best husbandry award in last years Barley-to-Beer competition, Mark Ireland (Arable, June 28, 1996) hopes fine-tuning of N input for a better grain sample will help him become overall winner this time round.

About 40% of the 1008ha (2490 acres) of the mainly light heathland is in barley. More than half of that is in spring varieties, mostly after sugar beet. This years entry is 16ha (40 acres) of Cooper after two barleys.

Being in one of the original NSAs, Mr Ireland has long had useful feedback on soil N levels from ADAS soil scientist Paddy Johnson, but has been sceptical of the need to measure individual fields. This season, partly because of an exemption to plough up some NSA grass, he decided to do so.

"We had soil mineral N tests done by ADAS on four fields." It involved sampling at two depths, 0-30cm (0-12in) and 30-60cm (12-24in). "At a total of £340 it was quite expensive," he comments.

More significantly he felt unable to stick to fertiliser recommendations based on the findings. "The tests showed we had only 12kg/ha of N after the grass, which is an extraordinarily low figure. They then said we should put 150kg/ha on the Cooper. That is way in excess of what I would ever use."

Corresponding advice to achieve a malting sample in the competition field, which indicated available reserves of 50kg/ha (40 units/ acre), was 130kg/ha (104 units/acre). "Last year I used that amount on our Optic for seed and the grain nitrogen came back as 2%," comments Mr Ireland.

"So we have reverted to using farm experience but done a small trial area with the rates suggested." Yield metering and grain sampling should determine which approach was best, he says.

His main concern is that the dry spring meant little of the 92kg/ha (74 units/acre) of N applied in February to the Jan 18 sown crop was taken up before May, so grain levels could still be high.

Early drilling, sometimes in December, is considered a risk worth taking to ensure deeper rooting and reliable spring barley yields. Average for the past three years is 5.4t/ha (2.2t/acre).

Heavy mildew hit both Optic and Cooper this spring, necessitating a split treatment of Patrol (fenpropidin) plus herbicide followed a few days later by Genie (flusilazole) and trace elements, to safeguard the stressed crop.

"It was disappointing because both varieties are rated 7 for mildew by NIAB." Top rated Chariot remained relatively clean, he notes. &#42

Mark Ireland is keen to see how grain nitrogens turn out this season.

MARK IRELAND

&#8226 First time soil N tests.

&#8226 Fertiliser advice query.

&#8226 Early drilling policy.

&#8226 Spring mildew surprise.


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