Yield maps used to fine-tune variable rates of fertilisers

27 February 1998




Yield maps used to fine-tune variable rates of fertilisers

VARIABLE rate applications of base nutrients and lime are set to become far more accurate by adding yield mapping data automatically and other field factors manually.

The result will be lower input costs and optimised yields, says SOYL, which will launch the new service at Precision Farming 98 in Peterborough.

"Weve seen a gradual increase in the number of farmers with yield maps and other data, such as remotely sensed images," says Simon Griffin soil scientist with SOYL. "Our aim is to use that information where appropriate to fine-tune fertiliser inputs."

Adjusting application maps manually according to the known history of a field has always been possible, notes SOYLs Simon Parrington. "But we now have software that can do it automatically.

Allowing for yield variations is important, stresses Mr Griffin. "Until now we have assumed yield and therefore nutrient off-take and demand are the same across the field. But if we can see how those vary, we can fine-tune fertiliser rates to take account of both soil supply and crop demand."

The more accurate approach ensures phosphate, potash, magnesium and lime levels can support optimal crop production in all parts of a field. If levels are too low, extra input is recommended. If levels are adequate, only enough nutrient or lime is specified to replace what was removed by the previous crop.

The new service can also accommodate remote sensing data and manual adjustments about inherently low or high yielding areas of the field, such as headlands, old hedge lines and stony outcrops. "Theres no point putting on extra nutrient in a bid to boost yield if there is an underlying reason for the low yield," notes Mr Griffin.

Indeed, the rate can be cut, since low yielding areas remove less nutrient each season.

Cost of the new service, which is available through distributors including Banks and CSC, is £1.25-2.50/ha (50p-£1/acre). That provides both a conventional hard copy recommendation map and an electronic map to direct GPS-guided variable rate application equipment.

Maps compatible with SOYL OPTI and RDS variable rate spreader controllers are already available. Compatibility with Massey Ferguson and LHAgro systems is expected by the autumn, says Mr Parrington.

Cost of the original soil sampling and analysis is £16-18.50/ha (£6.50-7/acre).

SOYLs recommendation service can now take full account of yield mapping data when planning variable rate fertiliser applications.

SOYL UPDATE

&#8226 P, K, Mg and lime application maps now account for yield map data automatically.

&#8226 Soil type, texture and field history can be added manually.

&#8226 More accurate maps cut input costs and optimise yield.

&#8226 Service costs £1.25-1.50/ha.

&#8226 Sampling/analysis £16-19/ha.


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