title: 14C-labeled organic amendments: Characterization in different particle size fractions and humic acids in a long-term field experiment.
abstract: Knowledge about the stabilization of organic matter input to soil is essential for understanding the influence of different agricultural practices on turnover characteristics in agricultural soil systems. In this study, soil samples from a long-term field experiment were separated into silt- and clay-sized particles. In 1967,14C labeled farmyard manure was applied to three different cropping systems: crop rotation, monoculture and permanent bare fallow. Humic acids (HAs) were extracted from silt- and clay-sized fractions and characterized using photometry, mid-infrared and fluorescence spectroscopy. Remaining14C was determined in size fractions as well as in their extracted HAs. Yields of carbon and remaining14C in HAs from silt-sized particles and Corgin clay-sized particles decreased significantly in the order: crop rotation > monoculture ≫ bare fallow. Thus, crop rotation not only had the largest overall C-pool in the experiment, but it also best stabilized the added manure. Mid-infrared spectroscopy could distinguish between HAs from different particle size soil fractions. With spectroscopic methods significant differences between the cropping systems were detectable in fewer cases compared to quantitative results of HAs (yields,14C, Corgand Nt). The trends, however, pointed towards increased humification of HAs from bare fallow systems compared to crop rotation and monoculture as well as of HAs from clay-sized particles compared to silt-sized particles. Our study clearly shows that the largest differences were observed between bare fallow on one hand and monoculture and crop rotation on the other.
authors.affiliation: Institute of Soil Research, Department of Forest and Soil Sciences, University of Natural Resources and Applied Life Sciences, Peter Jordan Strasse 82, 1190 Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Tatzber
authors.forename: Michael
authors.initials: M
authors.lastname: Stemmer
authors.forename: Heide
authors.initials: H
authors.lastname: Spiegel
authors.forename: Christian
authors.initials: C
authors.lastname: Katzlberger
authors.forename: Claudia
authors.initials: C
authors.lastname: Landstetter
authors.forename: Georg
authors.initials: G
authors.lastname: Haberhauer
authors.forename: Martin H
authors.initials: MH
authors.lastname: Gerzabek
keywords: Cropping system; Farmyard manure; Fluorescence spectroscopy; Mid-infrared spectroscopy; Photometry; Silt-, clay-sized particles