EM38: a new radar soil assessment tool

  • Tuesday 18 July 2006

South African viticulturalist Phil Freese is pioneering a new radar-based soil profiling system at his Vilafonté winery in Paarl.

In October this year Freese will be planting a 3ha plot of Malbec and Merlot, having examined the vineyard site and its soil profiles using a tool known as the EM38 Ground Penetrating Radar system.

The tool, which uses military-standard satellite global position systems (GPS), gives highly accurate pictures of soil moisture behaviour. According to Freese, it can map soil moisture movement ‘both as a result of gravity fall as well as soil density’.

Freese is working with Stellenbosch University researchers on the project. He is also working with scientists at University of California Lawrence Berkeley Labs ‘to the development of a very sophisticated hillside vineyard site in the Alexander Valley’.

He told decanter.com, ‘EM38 gives me a relative difference picture of how the soils vary both across the surface as well as depth. One set up of the instrument will give us a look as deep as 1.5m without disturbing the soil.’

The viticulturalist – who runs Vilafonté along with his wife Zelma Long and Warwick Estate owner Mike Ratcliffe – stresses that the EM38 does not obviate the need for the ‘ground truth’ work of digging 1.8m holes for soil analysis.

‘It just gives us the clues as to where to look for differences in potential performance characters that the soils can be expected to deliver.’

The chief value of the EM38 lies in its ability to detect variations in soils across a wide area. Freese says it is this ‘spatial variation’ that they are trying to eliminate or at least contain. ‘What we then do is design the planting to attempt to minimize the difference of soils within blocks.’

Freese is no stranger to high technology in the vineyard. At Vilafonté, whose first vintage was in 2003, they use the 'Leaf Water Potential' measuring system, a unique method of assessing vine stress by measuring water pressure in the leaves, as well as deploying the Normalised Difference Vegetation Index (NDVI), a system developed by NASA, which uses satellite imaging to measure relative vigour of the vines.

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