Bio-solids help maintain P levels

No-till Farmer recently posted this story that says Studies Show Bio-solids Can Boost Soil Phosphorus Levels For Years. This is not a big surprise to me.  We have hog farmer customers who are in a similar situation.  Human Bio-solids and hog manure are similar in nutrient content.  The article offers no explanation as to why the bio-solids help maintain higher phosphorus (P) levels in the soil.  While I am just speculating, I suspect that the difference is microbes.  I think the organic matter added by the bio-solids and manure supports microbes that release P into the soil over the long term.  We know that the soil contains P that is locked into silt particles that is unavailable to plants.  I suspect the microbes work on the silt particles to release some of that P over time.