The latest terrestrial N cycle paradigm considers soluble organic nitrogen (SON) as a rate limiting step for regulating the overall N availability in the ecosystem. SON is comprised of free amino acids and amino-N compounds such as peptides and small proteins accounting up 30-91% of the pool. Sixteen of the twenty biological amino acids have been identified in the SON. However, little is known about the relative contribution of the peptides and proteins to SON as well as the specific components of peptides and proteins, even though it is suspected that there is a vast number of different species in this pool.  It has been known that organo-mineral interactions play an important role affecting the N flux between the SON and ISON (insoluble organic N) pools affecting bioavailability of N to microorganisms and plants. However, the exact nature of these interactions remains unclear. In this light, this study is conducted to screen specific peptides that have high adsorption affinity for different soil minerals using the phage display library technology. It is hypothesized that specific small peptides in the SON pools have high affinity for certain soil minerals and exhibit specific surface organization that in turn affects the stability and bioavailability of the adsorbed peptides. Phage library display technique allows screening billions of random peptide sequences displaying a selective affinity for a particular mineral surface in a short period of time. In this study, we have successfully panned peptides with high affinity to montmorillionite and kaolinite and these peptides are in the processes to be sequenced. We expect identification of peptides with strong affinity for clay minerals which would lead to focused investigations on interaction mechanisms, stability and reactivity as well as identification of microorganisms that produce them.