On 10/4/2014 12:40 PM, Biggles wrote:
Thanks for the reply.

The soil quality is poor, its clay not soil so naturally rotavation is
the lazy mans choice.

Will glyphosphate kill the couch rhyzomes after repeat applications?

I'm not sure, but I think glyphosphate has to enter the plant through
its foliage, after which it moves through the plant's sap to its roots.
It kills plant tissues all along the way from foliage to roots but does
the most damage to the roots. However, I think the plant must be
actively growing (e.g., with foliage) for glyphosphate to be effective.
I know it is not effective if merely applied to the soil. Thus, if the
rhizomes are not supporting any foliage, glyphosphate will not work.

For clay, apply a generous amount of gypsum, at least enough to hide the
soil. Lightly wet down the gypsum. Then, starting about 2-3 days
later, slowly rinse the gypsum into the soil. This takes some patience
since you do not want to have the water with gypsum running off. After
all the gypsum has disappeared into the soil, wait about a week. Then
rotavation (which I think is what we in the U.S. would call rototilling)
will be more effective. That is because gypsum (calcium sulfate) reacts
chemically with clay to make the clay porous and granular instead of
pasty.

Even if you till much organic matter into the soil, you should apply
more gypsum every year or two. Otherwise, the clay will revert back to
its natural pasty state.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary