Wednesday, November 7, 2007
293-14

Hot Water Extractable Carbon: An Integrative and Sensitive Measure of Changes in Soil Quality.

Jonathan Deenik1, Parker Filer2, Greg Bruland3, and Amanda McClellan1. (1) Tropical Plant and Soil Sciences, University of Hawaii, 3190 Maile Way St John 102, Honolulu, HI 96822, (2) College of Agriculture and Life Sciences, Cornell University, 249 Warren Hall, Ithica, NY 14853-5905, (3) University of Hawaii Tropical Plant & Soil Science, University of Hawaii at Manoa NREM Dept., 1910 East-west Rd., Honolulu, HI 96822

Cultivation impacts soil physical, chemical and biological properties. Conventional practices that rely on tillage and high inputs of synthetic chemicals ususally have a negative effect on soil properties. Measurements quantifying changes in soil properties are often labor intensive, time consuming, expensive, and therefore, not routine. Hot water extractable carbon (HWEC) is a relatively rapid and simple measurement that quantifies changes in the labile C pool, which is correlated with microbial biomass C (MBC), mineralizable N, and water stable aggregates. In this study we test the hypothesis that HWEC can be used as a single measurement to monitor changes in soil physical, chemical and biological properties. We collected 18 soils across 7 soil orders with varying mineraligical properties and management histories. The soils were analyzed for HWEC, MBC, mineralizable N, and water stable aggregates. Results from regression analysis showed that HWEC was highly correlated with MBC (r2=0.81)and mineralizable N (r2=0.86), but showed a weaker relationship with water stable aggregates (r2=0.55) for all soils. Cultivation showed a significant and negative effect on all the measurements. We propose that HWEC is a simple and rapid method that can be used to quantify management effects on soil physiscal, chemical and biological properties