Hi Alex

For areas with limited tractor access, a simple approach to zoning is to do it by free survey by a competent soil surveyor.  This is used instead of, or in conjunction  with, vehicle mounted  EC probes or EMI scanners by some zoners in UK .  The surveyor conducts a free survey, concentrating on soil attributes  of management interest.  Zone boundaries are marked in the field  by GPS and confirmed later from time series of remote sensing imagery.

This method is slower and more expensisve than automated zoning.  However, the surveyor can take holistic view of soil varaiation and patterns, and can  alert managers to features not noted by sensors .  The boundaries and patterns  are less intricate than those produced by sensors but can be adjusted to be realistic and produce zones of dimensions that are relevant to the local management needs, taking account of boom widths in row cropping, and of rooting widths in orchard and vineyard crops 

Thank you, Ian. That is indeed a good approach. Going a step further would be merging the results of a good edaphologist and the results of sensors, especially in large areas. That is why I would like to know your experience with EM sensors.

Consider electomagnetic induction tools.  We have used the EM38 in various modes.  It slides over the ground surface so a person could walk and tow it or use a small all-terrain vehicle (ATV).  The tool itself would be able to handle inter-row spacing of 30 cm.  The towing vehicle may become the limiting width.

Thank you! what about the results? Are they comparable to Veris? Better? Worse? Any problem with metal trellis polesasts?

Pole or mast I meant...

I prefer EM rather than the direct contact requirements of EC sensors.  Depends what you are looking for.  We use EM for salinity mapping.  Others have used it for mapping textural changes or moisture levels.  Many other variables could be considered for mapping soil zones such as topographic/landscape features, soil chemistry, etc.

I draw your attention to a slide presentation done by a colleague at an Agronomy Update, January 2013 that is available online:

Shelley Woods:  Soil EC mapping technologies (EM38 and Veris) for identifying soil management zones - 759 MB PDF.   http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/crop14324/$FILE/au-2013-woods-effectiveness-of-em38-and-veris-soil-ec-technologies.pdf 

Hi Alex

We use Veris P4000 for EC mapping, the extra benefits with it is that we are able to measure Carbon, Nitrogen and Cations. You can mount/ attach it on a land cruiser bakkie  cause that is how we currently use ours, its very easy to work with.

Goodluck!

Hi there, 

thank you very much for your answers. When moving to EM are there alternatives to EM38? Similar results?

I like to recommend always the Veris 3100, because it delivers relatively robust measuring results from two depth (0 – 30 cm and 0 – 90 cm). The influence / interference from water pipes or cables in the soil or above the soil are not large / virtually non-existent in comparison with an EM38. The Veris need not be calibrated, das EM38 has to be calibrated. If the soil varies greatly, the calibration curve is no longer true in the field on that areas, if the variation very high, for example, negative readings with the EM38 are possible.

Nevertheless, I have collected good measurement results with the EM38.

The "new" EM 38 measures 2 depths at the same time; 0 - 75 cm and 0 to 1.50 cm (reviewed on the Genonics website). Its small size is a major advantage of the EM38. I have done with the EM38 research in the forest. I used a sledge for kids made out of plastic. In the arable field we used a wooden sled.

Thank you, Stefan!