Capability of selected indicators for soil organic carbon stability to explain soil functions

Summary

There is no doubt that total organic carbon (OC) is a valuable indicator for various soil functions. The stability of OC influences all soil functions that depend on microbial decomposition and might therefore have strong added value in soil health assessments. Starting from OC content, we investigated the added value of including one or more OC stability parameters measured by different techniques in explaining soil functioning. In 74 arable fields in the Netherlands, 3 soil samples were collected (n=222). We measured 3 soil functions, i.e. element cycling, biological population regulation, and the regulation of soil structure and water with 5 different indicators per function. Besides, we measured total OC content and OC stability with 3 different techniques (i.e. POX-C, Rock-Eval, and POM-MAOM fractionation) resulting in 20 OC parameters. Multiple linear regression was used to determine how much variation in each soil function indicator was explained by the OC parameters, and additionally by other measured intrinsic soil properties (e.g. texture and pH). We found that total OC content explained 9 ± 15% of the variation in soil functions, and that including OC stability parameters increased this to 26 ± 21%. Additionally including intrinsic soil properties explained 31 ± 23% of the variation in soil functions, so the majority (82 ± 22%) was explained by OC parameters. None of the 3 measuring techniques provided a single OC stability parameter that, in addition to total OC content, explained significantly more variation in soil functions than total OC content only. OC parameters from different measuring techniques were complementary and the explanatory power of different techniques was comparable. This study present novel inputs for including OC stability in soil health assessments to evaluate land management.