Preferential adsorption of nitrogen- and phosphorus-containing organic compounds to minerals in soils: A review

There is growing evidence that many nitrogen- and phosphorus-containing organic compounds in soils have on average a higher affinity for adsorption to mineral surfaces than nutrient-free organic compounds. This leads to preferential enrichment of organic nitrogen and phosphorus on mineral surfaces and has important implications for the architecture of organo-mineral associations in soils. Furthermore, the preferential adsorption of organic nitrogen and organic phosphorus compounds likely also influences carbon, nitrogen, and phosphorus cycling in terrestrial ecosystems since sorption of organic compounds to minerals slows down their decomposition. This contribution reviews studies on the sorption of soil organic nitrogen and phosphorus to minerals, guided by the questions; what compounds are soil organic nitrogen and phosphorus composed of and why do these compounds have a comparably high affinity to adsorb to minerals? How do soil properties influence adsorption of organic nitrogen and phosphorus to minerals and why does preferential adsorption of organic nitrogen and phosphorus matter for element cycling? Furthermore, this article identifies hypotheses for future research about the structure of organo-mineral associations, biochemical element cycling, and the role of stoichiometry for soil organic matter dynamics.