Why fertilise whole fields as if they were uniformly productive when clearly they are not?

Having tried SOYL’s mapping and variable rate fertilising system on one field at Rippingale last season, Ben Atkinson recently introduced it on all 2590ha (6400 acres) run from Grange Farm.

“Hopefully, it will even out our indices, improve yields and also save some costs.

And it should bring environmental benefits because we won’t be throwing fertiliser where it’s not required.”

The move ties in well with last harvest’s introduction of a yield-mapping system on the Claas 580 combine which produces maps that can be overlaid on the SOYL ones.

“Whether it’s giving us better overall yields will need more than a year.

But, hopefully, in five to 10 years, when indices are all more even and the maps are a more uniform colour we shall be able to tell.”

Soil sampling for phosphate, potash, magnesium and pH has long been standard practice on the mainly fenland unit. But the traditional W-pattern sampling once every three years was too imprecise on the large fields, he believes.

“Most of ours are 40-50 acres.”

The new quad-mounted exercise, under the directions of SOYL’s Allan Colburn, produced colour-coded maps for about 120 fields based on a sample taken on every hectare.

“It’s showing massive variations with P and K indices ranging from one to five,” Mr Atkinson says.

“We’ve always used a lot more phosphorus than potash, and it looks as though we have been over-doing it in places.”

Mr Atkinson is confident that SOYL’s concept and technology, having been developed since 1993, is sufficiently robust to rely on.

“I realise I’m in their hands, but it’s very simple to use.

All we do is tell them what our cropping plans for the individual fields are for the next four years, what the predicted yields are and whether we shall incorporate the straw.

They then work out how the applications should be managed.”

In practice that involves downloading computerised application plans to a Patchwork BlackBox handheld, which in turn tells a controller on a KRM 24m twin-disc double-overlap machine how to modify output as spreading progresses.

“From the maps we’ve got we predict that this year we should cut P and K use by a third.”

SOYL’s standard charge for mapping and making recommendations is 17.50/ha (7/acre).

But given that the new spreader was part of the deal and there was the prospect of an extra 170ha (420 acres) of land to assess, the firm’s bill was “very reasonable”, says Mr Atkinson.

andrew.blake@rbi.co.uk