Subject: re: adjusting soil pH on a very large scale From: "William W. Robinson" <roseguy@verizon.net> Organization: Date: Thu, 28 Feb 02 08:19:44 Message-ID: <MOD$020227.26175@rec.gardens.ecosystems>
The question was raised as to ways to reduce the pH of sandy soils when
the irrigation water is alkaline. We have this problem throughout most
of Southern California. Our native soil is mostly sharp draining and
contains very little organic matter. The pH of municipal waters throughout
most of the region runs around 8.0.
Many plants in our area are chlorotic because some of the essential mineral
nutrients get tied up in our alkaline conditions. It's a real problem!
One of the local commercial nurseries dug a water hole and meter in sulfuric
acid to get the pH down to more appropriate levels. The problem with this is
that they are also forming sulphate salts which do a number on the soil
organisms.
They would be much better off if they added large quantities of organic
material a couple of times a year. This will do a creditable job of lowering
the pH and it will also make the soil more water retentive and better
draining.
The cost of the organic material and the application is offset by savings
in water.
I use a 2" layer of composted tree trimmings in early spring and another
2" layer in early fall and we do this year after year. I don't dig it in. I
simply let it serve as a layer of mulch and as a food source for the various
soil critters. Eventually, the critters break the organic material down to
form organic acids and humates. . . some directly, while others indirectly .
.. .
but at bottom line, the bio-degraded organic material drops the pH down to
a more natural level and it will also works as a buffer to keep the pH at
or near that level.
A 2" layer is a lot of stuff! Do the math - length X width X depth. We've
got a small house on a small lot in suburbia Los Angeles - we'll use 6 - 8
cubic yards of composted tree trimmings just to give our beds a single 2"
layer and we do that twice a year. Over the years our soil pH went from
close to 8.0 to about 6.4 and it has become totally terrific!