28 March 1997

GPS soil maps help to plan strategy for PCN trouble spots

SOIL maps produced using ATVs fitted with global positioning systems are helping potato growers pinpoint areas within individual fields where high populations of potato cyst nematode exist.

But while the maps give growers detailed information on the number of cysts a gram of soil and the type of nematode species present, application systems which let producers vary treatments across the field are not yet available.

"They are not available for this growing season," admits Tony Fitzjohn, head of the precision crop services department at Banks Agriculture. "But they are coming.

"Even now, growers are using the information they receive to make decisions about the crop. Areas with high counts can be treated with a soil sterilant for example, or the farmer may even decide not to plant that field."

Intensive sampling

Sampling for potato cyst nematode is more laborious than soil fertility, he comments. An average of just 25 cores are taken from the field for nutrient testing. With PCN sampling the field is divided into 1ha (2.5-acre) blocks, in a grid system, with up to 50 samples being taken within each block. Every block is then analysed separately.

The precision crop services department at Banks Agriculture sampled over 3500ha (8600 acres) for PCN last year.

"The demand for this level of information is being driven by the big buyers," adds Mr Fitzjohn. "They are asking for information as to how the crop has been treated, particularly when it comes to pesticide use."

"Once a grower has his fields tested, it will only be necessary to re-sample the bad areas in future," concludes Mr Fitzjohn.

Anne Willington of Willington Crop Services, near Bury St Edmunds, also offered PCN sampling last year. She agrees that application systems are lagging behind sampling technology.

Aids management

"While most growers cant yet apply nematicide as precisely as may be required, the maps allow them to make much better decisions about crop management than ever before."

Dr Willington was surprised by the demand for the PCN sampling service. "Pressure from the big processors and supermarkets is forcing producers to come up with detailed, up-to-date information. Many actually want to know what species of nematode is present, as well as the population levels.

"We sampled 5000ha last autumn, when the service was in its infancy. Sampling either takes place in the autumn, ready for spring planting, or it can be done in March/April for next years crop."

The cost of sampling and testing varies, but starts at about £25 a sample block with an additional £7-£15 for the lab results. &#42

On the prowl for PCN – GPS maps can help plan management strategies, says Anne Willington. Once application equipment catches up, accurately tailored treatment will be possible.