You have to continuously add organic material. A deep organic mulch
will limit the amount of washed out soil and continuously replenish
what you have, so would a living mulch like dutch clover.
Mark wrote:
I have a slope in my backyard.
about 15 years ago I have set up some terraces, brought good and
expensive soil and planted vegetables.
First year it was great but after that the organic matter have leached
out and plants started to get sick.

I want to do it again, but do not want to loose a soil.

Any ideas?