Mark wrote:
I have bought an electronic soil tester. Measures PH level and Nutrient
level (fertility).

The PH it generally shows OK around 7.
But fertility is low.

1.What should I do now with plants potted in containers? Is adding
standard 15-15-15 fertilizer enough for that?

Since David has already disabused you of the notion that the tester is
accurate,
I will answer this. Probably 1/2 compost gives you enough
micronutrients that you can barely get away with it for one season. So
add 15-15-15, but then that soil will be depleted at the end of the
season. Usually, I take out one inch of soil, add one inch of compost,
one tablespoon of wood ash and one of fertilizer rich in N and P to my
houseplants, when I put them out for the summer (some years, if I am
using manure, I just give them 1 inch manure, no fertilizer). The ash
supplies most micronutrients in quantity but is also alkaline.


2. When next time I prepair soil for containers. I usually mix half a
soil from the ground and half the compost I got from the dump. Should I
mix 2 parts compost to 1 part soil?, So I do not have to add fertilizer
right away after planting?

Thanks