The most economical and generally quite accurate water gauge I have found is my index finger. Inserted into the ground to the second knuckle, it will reveal if I need to water. Cool and/or moist- no water needed. Transplants may need a bit more until they are established. Seeds usually need to be kept damp until they germinate. Since everyone's soil and microclimates can vary, there really is no good general rule.

tj

I agree with the above, it is hard to say other than to look at the soil (or feel it). Dry down a couple inches it can be watered. This is for established plants. Seeds need to be kept moist at seed level until they germinate.

You get to know how your soil is over time. In addition I would be sure not to keep it too wet either. Diseases are less if the soil dries out a bit in between waterings.

That is my opinion and I know you will never convince a potato farmer of it. :)

Spinach and lettuce will grow better and last a lot longer before bolting if you keep the soil moist. So unlike big plants with deep roots, which you can water deeply once or twice a week, water your salad things much more often so they don't dry out. I have had trouble with things bolting way too fast and read an article about salad plants in Organic Gardening that told me this hint. Already my spinach is doing so much better than ever before. So you need to water little plants more often than big plants, just like you water seeds a lot more than plants. Hope that helps.

Marcia