Adam Davis wrote:

> Actually, an even better desing would be to sense the moisture in the soil.  I
f
> it rained a lot last night, you shouldn't need to rain all day, and maybe even
> the next.  It will also tell your system when you need to water more than usua
l,
> and less than usual
>
> I know you can get a pretty accurate reading by simply sticking two probes in
> the soil, and measuring the resistance between them.
>
> -Adam

[Removes Computer Science Hat, dons Botanist :-) ]
You actually need to measure *available* soil moisture.  This is done using a
tensiometer.  There are many commercial devices - they are used by irrigation
persons.  I don't have any URLs - the last time I worked with this stuff was a l
ong
time ago and involved an LSI-11/03!

/Kevin


--
-----------
Kevin J. Maciunas           Net: kevin@cs.adelaide.edu.au
Dept. of Computer Science   Ph : +61 8 8303 5845
University of Adelaide      Fax: +61 8 8303 4366
Adelaide 5005
SOUTH AUSTRALIA