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NOTE: To get off this list, send email to majordomo@aqua.ccwr.ac.za with the body of the message containing the line: unsubscribe sowacs Dear Jac, As a Diviner installer, I was interested to read what your supplier is doing. I expect he is using Bentonite, possibly mixed with cement. Personally, I avoid slurry installations because the soil moisture content of the slurry will always be higher than a sandy soil as the bulk densities are different. I only use slurry when the soil is very stony and I cannot avoid air gaps round the probe. In such cases, I sieve some topsoil and mix it with water to act as the slurry. The danger in my method is that one is putting topsoil to the bottom of the probe and encouraging roots to go there. I work mostly with short term crops and I am primarily interested in the top 30cm only. The Bentonite treatment is better as it is inert and does not encourage rooting. It is important to know what you are using your Diviner for. Is it for research or for managing irrigation? If it is the latter, then the technique employed by your supplier will work very well. It will tell you when any particular layer of soil is running out of water (usually 10cm) and how deep rain or irrigation penetrated and whether the profile was brought back to full. i.e. the dynamics of soil moisture will not be affected. The principal advantage of the slurry technique is that it is consistent, quick and easy. It comes down to economics and what your supplier is charging. I think it is better value for money to have lots of tubes put in cheaply than one or two installed expensively! The Sentek approved installation method is brilliant but time consuming and, in my opinion, not always commercially justified. I use it for one or two reference sites with the EnviroSCAN, but for the Diviner, cutting some corners may be justified. Rupert Knowles Olivers Orchard Ltd (in association with Peter White Water Management) Olivers Lane Colchester CO2 0HH UK fax: +44 (0)1206 330208 mob: +44 (0)860 687760 email: r.knowles@aspects.net -----Original Message----- From: owner-sowacs@aqua.ccwr.ac.za [mailto:owner-sowacs@aqua.ccwr.ac.za] Sent: 27 May 2000 01:53 Subject: Diviner 2000 access tubes I recently acquired a Diviner2000 moisture probe. The supplier installs the access tubes by drilling a hole of 10mm bigger OD, inserts the PVC tube and settles it in with a clay mixture (similar to potters clay - the exact compostion I am not sure of), to ensure perfect contact between tube and soil. We work with sand (as in sand dunes) with moisture holding capacity as low as 45 mm/m. I am wondering what the effect of the clay band in direct contact with the tube could be. Can I assume that the sand-clay will reach equilibrium, in a short enough time to give me the correct response. Your comments will be appreciated. Thank you: Jac le Roux jac@besproeiing.co.za