Thank you David E. Ross and Gunner for answerin' my question. Now I understand that pine bark has a little efficiency as a fertilizer by its own, but can be used to improve soil and also for make compost.

David Ross, I ask this question 'cause I'm in the middle of a discussion about this topic. If pine bark can be consider: a) A fertilizer (good or bad) just like the rest of the living organisms and organic wastes. b) Its a fertilizer of slow absortion or c) Its useless in any way, just to add it to the compost. Till now my money was on the first.

Gunner, I've use pine bark all my life for two purposes: First I put in the bottom of the potts and cover it with sand tom improve the drainage. Second to make more acid the substratum for especific plants like fruit plants, peppers and my little garden (grass).

Regarding about the size or the consistency of the pine bark I use its just what I can take from the soil under the pine trees. In my neighborhood we have a lot of pines and I can take what we call here "pinasca" that its a multiple combination of big pieces of bark, small chips, some "litter" or leaves, and pieces of branches. I was told that its really good for make the soil more "acid" regarding to the chemical PH.

Many thanks for your information!