Targeting potash, phosphate and magnesium fertilisers to different soil types within fields offers useful savings without compromising yields, if uptake of a relatively new service is anything to go by.

Wiltshire-based Courtyard Partnership’s precision farming technique, launched four years ago, is already operating on 20,000ha (50,000 acres), according to the firm’s Vince Gillingham. And demand for the £2.50/ha service is growing, he maintains. “We’re seeing average savings of £10/ha.”

A hybrid between a full GPS precision system based on intensive soil sampling and the traditional method using whole field analysis, the system provides users with “virtual field” maps.

The maps are derived from a combination of farm staff and agronomist knowledge and geological, soil and yield maps. The zones are ratified by a soil scientist and boundaries logged by GPS.

“We call it intelligent precision farming with the intelligence coming not from us but from the farmers,” says Mr Gillingham’s father Mark. “We take the information they already have about their fields and soils and turn it into a management tool.”

View reinforced 

The partners say recent research by independent soil scientist Steve Heming has reinforced their view that the concept is valid and more cost-effective than some more detailed and expensive options.

The work answers a key criticism – namely that the variation within the virtual fields or zones was too great to be of practical use.

“We had to be sure that it was not greater within the zones than within the whole field,” says Vince Gillingham. “I’m pleased the work found that the range within the zones was only about 50% of the range within whole fields.”

The research also analysed the firm’s database of P, K and Mg sample results from nine farms covering sand, limestone and chalkland soils.

The results for the sandy land are still being assessed. But already some useful findings have emerged from the limestone and chalkland soils, notes Vince 

One notable point is that on many of the Cotswolds thin soils where drought often restricts yield, nutrient indices are often unnecessarily high because of excessive historical fertiliser applications.

Using zoning can avoid this and save money, explains Mark. “So long as you don’t drop below the recommended indices the technique is yield-neutral.”



  • P indices 1.5 points lower on deeper acidic clays than brash – lower off-take on brash due to drought?
  • P unaffected by soil texture
  • K significantly lower in gravels than other soils. Higher indices on classic Cotswold brash – water stress limiting off-take?
  • Trend for K to increase with clay content
  • Mg lower on stonier and shallow land, but high on deep soils
  • Trend for Mg to increase with clay content and soil depth


  • P indices on grey, very chalky soils generally one point lower than deeper brown earths
  • Clear link between soil organic matter and increased P
  • Mean K levels lower on ‘grey’ very chalky soils – increasing with clay content
  • Trend for K to rise with organic matter
  • Mg levels lowest on very chalky soils. Only adequate on heavy clay-with-flint
  • Mg tends to increase with clay content

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