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Title: A CP-MAS 13C NMR INVESTIGATION OF ACETATE FATE IN ORGANIC AND CONVENTIONALLY MANAGED SOILS

Author
item WANDER, MICHELLE - UNIV OF ILLINOIS
item DUDLEY, ROBERT
item TRAINA, S - OHIO STATE UNIV
item KAUFMAN, DONALD - RODALE INSTITUTE RES CNTR
item STINNER, B - OHIO STATE UNIV
item SIMS, GERALD

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Interest in management of soil organic matter has increased in recent years, largely with the goal of improving the quantity or quality of soil organic matter. The specific effects of management practices on soil organic matter have not been well-documented. A study was conducted to examine cycling of carbon in soils that received inorganic fertilizers, manure, or were legume cover-cropped. An instrumental technique, 13C NMR was used to trace a microbial substrate, acetate, that had been labeled with carbon 13. The results indicated that organisms in the manure-treated soil released more of the added acetate as carbon dioxide than in the other soils, suggesting rapid turnover of carbon in this system. Organisms in the cover-cropped soil incorporated more of the acetate into soil organic matter than the other soils, suggesting a greater potential of that system for carbon storage. The results obtained in this study demonstrate the utility of the 13C NMR technique for addressing questions in soil organic matter turnover and composition, and will encourage further development of this approach by other scientists. This technique will allow scientists to unravel some of the complex interactions in the cycling of carbon in soil. Some of the questions we expect to see addressed with 13C NMR include build up of soil organic matter, identifying the soil biologically active fraction, and how pesticides become incorporated into soil organic matter. A better understanding of these carbon cycling processes is essential to protecting the soil resource for future generations.

Technical Abstract: Organic management practices and mixed-crop rotations have beneficial impacts on biologically-active soil organic matter (SOM); however, the specific impacts of these practices on SOM composition and turnover characteristics are not known. The effect of organic and conventional management on soil C cycling was assessed using soils collected from the Rodale Institute Research Center's long term Farming Systems Trial (FST) experiment that included organic-legume cover, and conventionally managed-inorganically fertilized farming systems. Soil respiration rates, atom % 13C, and CP-MAS 13C NMR were used to trace the fate of 13C-labeled acetate that was added to the FST soils and incubated for either 2 weeks or 3 months. Farming system history significantly affected both the amount and form of acetate-derived 13C that was incorporated into new soil organic matter. Initially, more acetate derived 13C-was metabolized in the organically managed-manure amended soil than in the other two soils. In the organic-cover cropped soil, a greater proportion of acetate-derived 13C was retained and incorporated into new C structures (carbohydrate and carboxy-C) than in the other two soils. These findings directly support the conclusions of previous studies by showing that organic management increased short-term C turn over rates in the manure amended soil and increased the C storage potential of the cover cropped soil.