Rapid mineralization of mineral-bound carboxyl-carbon of salicylic acid and phenylalanine

Ligand-bound carboxylic acids are considered a stabilized fraction of mineral-adsorbed carbon in soil. Carboxyl-14C labeled phenylalanine or salicylic acid wereadsorbed onto goethite, kaolinite, or illite, and subsequently incubated in both loamy and sandy arable topsoil for three weeks. Contrary to our expectations, moremineral-adsorbed carboxyl-C was mineralized than remaining C in salicylic acid and phenylalanine irrespective of mineral type or soil due to competitive desorptionfollowed by preferential mineralization. Factors that control the desorbability of organic molecules are more important for their stabilization in the soil than sorption strength.