20 November 1998


Introducing GPS systems to

your farm requires careful

thought, says Edward Long

SHINY new equipment fitted with GPS-based systems has the potential to drive down production costs. But check whether the technology suits your farm before investing, warns ADAS.

"The new technology offers a lot of potential for increased precision, which in an era of low prices could help enormously. But it may not suit all farmers and all soils," says precision farming specialist David Parish of ADAS Boxworth.

Rather than focusing on individual GPS-based operations, growers should consider the role of GPS systems on the whole farm, he maintains.

But first consider the scope for benefits on individual sites. Although some land, particularly grade 1 silt, is very uniform most has significant changes even within fields. There is likely to be more variation in lightland areas where thin soil suffers more from drought, leaching and nutrient deficiencies than on heavyland clays, he notes.

"Over many years land has been farmed with a uniform level of inputs with some parts over-done and some under-done. This blanket approach has been a compromise, so time, money and resources have been wasted," says Mr Parish.

"Our job now is to discover how to exploit the new GPS-based technology to boost input efficiency to maximise gross margins within part fields. In an era of low commodity prices this increased precision could help enormously to optimise profits."

Having decided a farm may benefit from more tailored use of inputs the next challenge is to choose between a whole-farm and a one-off approach.

The latter is typified by nutrient mapping. Mr Parish is not convinced it is the best use of GPS. "Soil variations mean sampling a 1ha (2.5 acres) block may not be representative of most fields, so the accuracy achieved is little better than with the existing blind approach."

A more strategic use of satellite-linked sampling to identify parts of the field with most variation, which need treating differently, would be more use, he suggests.

"It would allow arable farmers to use existing farm equipment instead of having to purchase new spreaders, sprayers and drills capable of performing on-the-move application rate changes."

Whatever the equipment used reliable base-line data is needed, ie several years of mapping.

"It would be extremely unsafe to rely on a single years yield map to target inputs. Every additional years map adds credibility to the emerging picture." Results can then be related to soil type and other variables, and obvious limiting factors such as rabbit damage, wet holes and low pH.

Once a good idea of the potential of the field is obtained inputs can be matched to need either using new machinery across the whole field or existing equipment on defined parts of a field.

"This is just the first step, there are many more benefits to come," says Mr Parish. Remote sensing of crop development from satellites or aircraft could help modify input use within the same season, he notes.

Growers must ask several key questions before investing in GPS-guided equipment to take advantage of the precision farming revolution.

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