A long-term plot experiment was conducted in the Sanjiang Plain to study the effect of applying organic manure for years in row on soil humus composition, transformations of Fe, Mn and Al oxides and phosphorus availability. The results indicated that soil humus, mainly loosely combined humus were increased after 4 years of adding cow feces, because of the supply of lowmolecule organic acid released from the added cow feces. The contents of DTPA-extractable and organo-chelated Fe, Mn, Al was also related to organic acid corroding soil coating and solublizing soil oxide. Some half-products derived from the fresh material can supply H⁺,and can chelate or solublize soil Fe, Mn, Al or compete for adsorption site on soil colloid, and form Fe, AI-OM-P or soil colloid-OM-compounds, thus bring about significant increase in soil available P. So the bio-measure is an effective strategy to ameliorate albic soil, enhance its nutrient, especially P, availability and its buffer capacity and stress-resistance.