I am posting this here because my new ISP does not provide access to active
hydroponics newsgroups.

I just visited a hydroponics store to buy a large reservoir for my nutrient
solution, a Texas controller. They told me to replace the nutrient solution
every ten days in order to remove the waste products given off by the
plants. I think that that is more labor intensive than necessary. I was
thinking that I justreplace the nutrient whenever the conductivity drops
below a certain level. I would also replenish used nutrient several times
before disposing of it. I do dispose of it by spreading it on plants growing
in the soil.

My question to the group is: What waste products do plants produce that
leave by means of the roots?

Bill