On 2/9/2016 9:41 AM, Donald Chester wrote:
You know the actual contours would rarely, if ever, precisely follow the
boundaries shown on the map,
jumping abruptly from low conductivity at one point, to high conductivity just
a few feet to the other side of the
line. Those maps, based on random samples, are virtually useless for
predicting the soil conductivity at any
specific site location. They might be somewhat useful as a preliminary
guideline, but no substitute for actual
measurement.
Don k4kyv
Don't be so sure about this. My QTH is at the southern end of
Sacramento county in an area the FCC map shows as conductivity
of 15. I am just west of Galt. If you go south into San Joaquin
county (around Lodi), the conductivity drops to IIRC 8.
If you go west toward the Sacramento River Delta, the conductivity goes
to 30. These "abrupt" differences in conductivity happen to
correspond pretty closely to what is common knowledge around
here about soil conditions. If you talk to farmers, nurserymen,
orchard managers, etc., they will tell you that Lodi soil
is great for growing, and Galt soil is a forget it, unless you
have the hard pan broken up. The vineyards of Lodi basically
stop at the county line corresponding to soil conditions. It's
almost like there was a law forbidding wineries in Sacramento
county. The county line is a river, so it makes sense that
conditions could change abruptly there. To the west,
the FCC boundary roughly corresponds to signage saying
"Welcome to the Delta", a few miles from here. This boundary
is also not arbitrary; there is another river there that kind
of delineates the Delta. That land is a completely different situation
agriculturally, a lot of it reclaimed from swamp land. Much of the land
actually consists of islands below sea level. North of that area, there
is another conductivity 30 area in Yolo county that corresponds to
land that will grow nothing at all except rice, for which
it is perfect because there is solid clay down at least
30 feet. (It's pretty deep here too).
On my own land, I think the FCC map has it right. Verticals work
great, and beverages barely play.
Rick N6RK
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