2 August 2002

Digital maps show way to curb costs

A NON-INVASIVE technique for mapping soil variation is cutting fertiliser and machinery costs by £35/ha and easing farm logistics on a 2000ha Oxon estate, according to farm manager Peter Hewson.

The technique, Dalgety DDF, produces detailed field maps of sub-soil variation using data collected by a low ground pressure vehicle. Data-related agronomic decisions then help growers target variable costs more effectively, including machinery and fertiliser inputs.

Mr Hewson first became interested in DDF last year when he used it to assess the impact of several years of minimum tillage at Chota Estates, Burford.

"The soil maps helped dismiss any concerns with min-till regarding compaction, but the scope for reducing variable costs became obvious when field data were interpreted fully," says Mr Hewson.

"For example, mole ploughing is now targeted to specific fields or areas within fields comprising heavy-clay subsoil. Previously, whole fields had been mole-ploughed, but the mapping from DDF showed that a number of them included areas of free-draining subsoil.

"By avoiding the brash sub-soils we saved £375, based on contractor rates of £61/ha in one particular field, recouping the cost of DDF almost immediately."

Mr Hewson estimates the one-off cost of DDF at £15/ha has reduced machinery costs by £12-15/ha. He anticipates similar savings in subsequent years.

Following the initial success, he now plans to map a further 400ha of the estate over the next two years.

After the adoption of DDF, Chota Estates is now some way towards precision farming, he believes. But the significant capital investment usually associated with the practice has been avoided.

Since the introduction of DDF, Mr Hewson says he has also been able to target fertiliser applications more effectively. "The maps provide detailed information on P and K indices in relation to the estates soil type. By modifying application rates, our fertiliser bill has decreased by a further £20/ha.

"Fertiliser rates can now be modified within or between fields depending on how hungry different soil types are. Areas with heavy-clay subsoil, for example, are found to exhibit high K indices of three or above, so lighter fertiliser applications can be made without compromising crop yield or quality."

Tackling the wide variety of soil types across the six units that make up Chota Estates make machinery logistics a real challenge, says Mr Hewson.

"By mapping the soil types we can now send appropriate machinery out first time, saving on labour and wasted manpower. All the DDF scanning and soil sampling was carried out by Dalgety and did not require any on-farm labour, which was a welcome surprise," Mr Hewson concludes. &#42

Soil mapping technology is helping Oxon farmer Peter Hewson cut production costs by £35/ha, the Dalgety Digital Farming service providing the practical data to aid management decisions (left).

How DDF works

An electro-magnetic signal is used to assess the electrical conductivity of soils to a depth of 1.5m across the field, says Dalgetys Gordon Thornton. The resulting data is used to produce a map to guide subsequent soil sampling to identify the cause of any variations, which may be due to compaction, soil type or subsoil structural problems. Further analysis can help identify variations in nutrient status. Cost is about £15/ha.

&#8226 Variable soils in Oxon.

&#8226 Six wide-spread units.

&#8226 DDF helps tailor cultivations and fertiliser use.

&#8226 £35/ha cost savings.