Quantifying Soil Protein In the Context of Soil Quality Assessment.

The size of the soil protein pool shows promise as a biological indicator of soil quality.  As the product of several biological sources, it integrates the abundance of various functional groups of soil organisms.  It represents a point of intersection in the C and N cycles, and it is likely that a sizeable fraction of PMN is mineralized from proteins, which can thus buffer N availability. Furthermore, proteins represent a pathway toward C sequestration, as they may be stabilized when occluded, for durations exceeding a century.

We measured multiple fractions of autoclaved citrate extractable (ACE) proteins in soils from experimental tillage and rotation plots at several time points across a growing season, within the framework of development of the Cornell soil health test.  We found that the soil protein pool responds to tillage intensity, residue removal, and rotation, and that the size of the protein pool varies by several percent across the growing season.  We assessed the relationship between the protein pool size and wet aggregate stability, and found that the relationship varies by location, presumably with soil type.  We identified issues related to the accurate quantification of this organic matter fraction, and will discuss the importance of these for consideration of carbon sequestration.  We have provisionally concluded that quantification of soil proteins may be useful in soil quality assessment, and we will discuss ongoing efforts and inferences regarding this use.