IN AUTUMN 1995 Adam Haylock asked Banks Agriculture to sample soil on 84ha (210 acres) of his 500ha (1,250 acres) of chalky boulder clay at Copy Farm, Helions Bumpstead.
A Quad Bike fitted with a SOYL-MOBI unit, a global positioning system (GPS) receiver with a correction factor provided by an RDS radio tuned to Focus FM, was driven around each of four fields.
An on-board computer drew a map showing the most representative sampling points for each hectare, and the track to reach them in logical order.
At each one 16 individual samples were dug. These were sent to Hampshire-based soil nutrient mapping specialists SOYL with details of previous cropping, future intentions, and straw disposal plans. From this maps were produced.
They showed levels of phosphate, potash, magnesium, and the pH status and were discussed with Jesse Pattisson from Banks Newmarket office. An action plan to target fertiliser to where needed was drawn up.
They revealed a surprising variation of indices ranging from 0 to 2+. "Productivity could have been compromised without us knowing. I was brought up to believe that so long as we looked after the P the K would look after itself.
"For 12 years we have applied 2cwts/acre of triple superphosphate routinely to provide maintenance plus. But maps show the amount needs to be tailored more precisely, and that some K is required."
They revealed lines of old field boundaries, one area of unusually high fertility was puzzling. The block originally comprised of 10 or 12 fields, one of which was where Mr Haylocks great-great-grandfather threshed corn and spread the chaff. A localised severe black-grass infestation could also be a legacy of the chaff spreading.
Although P and K indices have been increasing in recent years Mr Haylock was not convinced they were sufficiently accurate as soil sampling was too general and did not take into account in-field variations in soil type.
He feels the individual GPS-determined sampling sites provide a more accurate picture of actual fertility.
"We need a better idea of what is needed as we may have been over or under-doing fertiliser on areas of the farm. Margins are getting tighter and it makes economic sense to improve input precision.
"It is also obvious we must adopt a more rational and targeted approach to inputs if we are to meet the needs of modern markets. Soon we will have to justify fertiliser use on malting barley and milling wheat," adds Mr Haylock.
Last autumn P and K targeted to actual soil needs for two years was applied to the mapped block, the rest of the farm received the conventional routine rotational dressing of triple superphosphate.
The block was cropped with wheat, rape and linseed. Wheat averaged 9.75t/ha (3.9t/acre), slightly better than average, but so did the crop given the standard fertiliser treatment.
"I doubt if we managed to save any cash as the total amount applied was about the same, but it was more precisely targeted and some muriate of potash was included. There has been little to see in the crops, but they may have done better than they would have done in my normal system. After five years we will re-test the soil to see what impact there has been on nutrient levels."
The mapping service, which costs £16/ha (£6.50/acre), is of little practical use unless fertiliser rates are matched to soil need. Banks has set up a network of contractors who are equipped with either Kuhn or KRM variable spreader units.
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