Hi Rodger and all, Well, I changed it back and forth a couple of times. I settled on "absorb" because the kaolins can do an ion exchange, switching Ca++ for K+ in the internal matrix of the clay. On the other hand, ion exchange phenomena are probably best thought of as "adsorptions" as well, so (this morning) I tend to agree with you. I have heard about the "different" clays of the North American West, but I've not had any personal experience gardening in them. Jim Shields in central Indiana (USA) At 06:55 PM 2/2/2008 -0800, you wrote: >On 31 Jan 08, at 9:09, J.E. Shields wrote: > > > Clays can adsorb ions on their surfaces and can absorb [sic; ITYM > > "adsorb"] ions internally. > >Not all clays. Lateritic clays have very poor adsorption powers, >hence the poor soils in the Oregon Coast Range (Ref: Roadside Geology >of Oregon), Africa, and the Amazon Basin. > >For those of you on the Left Coast, there's a very nice exposure of >bright red lateritic soil on the east side of I-5 a little north of >Grass Pants, Oregon. Just a small cut with some erosion that exposes >the subsoil, but quite prominent because of the brilliant color. > > > > >-- >Rodger Whitlock >Victoria, British Columbia, Canada >Maritime Zone 8, a cool Mediterranean climate > >on beautiful Vancouver Island >_______________________________________________ >pbs mailing list >pbs@lists.ibiblio.org >http://www.pacificbulbsociety.org/list.php >http://pacificbulbsociety.org/pbswiki/ ************************************************* Jim Shields USDA Zone 5 Shields Gardens, Ltd. P.O. Box 92 WWW: http://www.shieldsgardens.com/ Westfield, Indiana 46074, USA Tel. ++1-317-867-3344 or toll-free 1-866-449-3344 in USA