Dont be too precise – ADAS
BE ON your guard for spurious precision farming, warned ADAS consultant Peter Dampney.
"Trying to get too precise when precision farming has its own variations is stupid. Sampling errors, errors in decision making and application errors can all hit precision."
Adjusting P and K rates according to soil mapping is a particular concern. "Many fields have adequate P and K levels and variations are not be that great," he said.
Furthermore, nutrient offtake may vary more than first thought. "Average potash offtake varied from 3.9 to 5.2kg/t across three fields last year. If you want precision you need to know how much your crop is removing rather than relying on the accepted average figure of 5.6kg/t."
SOYL refuted ADASs claims. "MAFF figures show a lot of fields are too high or too low in P and K due to under or over application and ADASs own figures show variations across fields can be quite high," said SOYLs soil scientist Simon Griffin.
Furthermore, sampling could be targeted to suspect areas and variable offtakes be allowed for where figures are known, he added.
"Using a yield map, soil map or aerial photography may be a far better way to start tailoring inputs," Mr Dampney suggested. ADAS support for yield mapping does not reflect a contract from Massey-Ferguson to help users get more from yield mapping, he stressed.