Technical ArticleWater-Extractable Soil Organic Carbon and Nitrogen Affected by Tillage and Manure ApplicationZhang, Mingchu1; He, Zhongqi2; Zhao, Aiqin1; Zhang, Hailin3; Endale, Dinku M.4; Schomberg, Harry H.4Author Information 1Department of High Latitude Agriculture, School of Natural Resources and Agricultural Sciences, University of Alaska, Fairbanks, AK 99775. Dr.Mingchu Zhang is corresponding author. E-mail: email@example.com 2USDA-ARS New England Plant, Soil, and Water Laboratory, Orono, ME. 3Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK. 4USDA-ARS J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. Received December 14, 2010. Accepted for publication March 31, 2011. Soil Science: June 2011 - Volume 176 - Issue 6 - p 307-312 doi: 10.1097/SS.0b013e31821d6d63 Buy Metrics Abstract Water-extractable organic matter (WEOM) contains labile organic carbon (C) and nitrogen (N) and is sensitive to soil management. The objective of this study was to determine the quantity and spectral properties of soil WEOM responding to types of nutrient addition and tillage managements. Soil samples were taken from treatments (conventional tillage, no-tillage, poultry litter, and NH4NO3 application) of a 10-year experiment in Watkinsville, Georgia, at different times and soil depths. Air-dried soil samples were extracted by deionized water followed by filtration (<0.45 μm), and soluble C and N, absorptivity at 254 nm, and fluorescence excitation/emission matrix in the extract were determined. Results showed that poultry litter application accumulated higher amounts of water-extractable organic C and N than NH4NO3 application. But no significant difference was found between tillage and no-tillage for both water-extractable C and N. Absorptivity at 254 nm decreased during cropping years for conventional tillage and NH4NO3 application, indicating accumulation of aliphatic organic compounds in WEOM, but the fluorescence-measured humification index showed an opposite trend. For no-tillage and poultry litter application treatments, there was no difference in absorptivity over the sampling time. Parallel factor analysis of excitation/emission matrix data showed that WEOM consisted of three fluorophore components: humic-, fulvic-, and tyrosine-like "compounds," and relative distribution of these components differed among treatments and changed over soil depths. The tyrosine-like component tended to accumulate in the lower sampling depth (>15 cm). Overall, the quantity and spectral properties of WEOM responded to the types of nutrient application and tillage practices. © 2011 Lippincott Williams & Wilkins, Inc.