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Moshe Meron writes to the sowacs list: ===8<============== Mike, Theoretically that might be a problem, however in the situation you described it never happened during the years we worked with Watermarks. They respond very fast to wetting in drip irrigation, even on the outer edges of the wetted "bulb". If they fits your application in other aspects, don't worry about rewetting. Moshe Meron ========================================== MIGAL Galilee Tech. Center - Crop Ecology Laboratory PO Box 831, Kiryat Shmona 11016, ISRAEL Phone: +972-4-6953559 Mobile: 050-764086 Fax: 04-6944980 Email: MERON@migal.co.il ========================================== -----Original Message----- From: Bruce at Findasensor [mailto:asowacspost@findasensor.com] Sent: Thursday, March 20, 2003 8:35 AM To: brooz@pobox.com Subject: SOWACS: Granular matrix rewetting in clay Mike Schulz writes to the sowacs list: ===8<============== greetings, As pore size has a major impact on soil moisture movement i have a query regarding whether granular matrix resistance blocks could potentially have problems rewetting in clay soils. Its apparent that gypsum blocks have very fine pores as they loose little water before ~60kPa, ie. they don't work in this range. Granular matrix sensors are therefore made of coarser material in order to allow them to function in the >10kPa range. That is they have larger pores. In a clay soil that has been rewet after drying to say 250kPa, can water move from the wet but not saturated clay into the dry but larger pored matrix of the granular matrix block. If the soil around the block is saturated at each irrigation or rain rewetting should proceed rapidly. My query is what happens when the block is positioned on the edge of say a dripper wetted ball and the soil texture is finer than that in the block. Comments on your experiences would be appreciated. Regards Mike Schulz Serve-Ag, Victoria. PO Box 615, Mooroopna, Vic, 3629. Tel: (03) 5825 4783 Mobile: 0408 395 076 Serve-Ag provides a range of services to the agricultural and environmental communities. For additional information consult our website (www.serve-ag.com.au), call me or, call our head office (03 6427 0800) ===8<============== NOTE: To get off this list, send an email to list@sowacs.com with the subject line: unsubscribe_sowacs For full instructions see this page: <http://www.sowacs.com/subscribe/index.html>