Wander, M. M., Dudley, R. B., Traina, S. J., Daufman, D., Stinner, B. R., and G. K. Sims. 1996. Acetate fate in organic and conventionally managed soils. Soil Science of America Journal 60(4):1110-1116.
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 Rodale's Farming Systems Trial experiment, which
included organic-manure amended, organic-legume cover cropped, and conventionally
managed-inorganically fertilized farming systems. Soil respiration rates,
atom % 13C, and cross polarization 13C nuclear magnetic resonance (CP-MAS
13C NMR) were used to trace the fate of 13C-labeled acetate added to soils
incubated for 2 and 13 wk. Microbial activity and C turnover rates were
initially greater in the manure-amended soil than in the other two soils.
Acetate mineralization lagged in the cover-cropped soil during the first
2 wk. Low atom % 13C in the conventional soil showed that, even though
its soil respiration rates, and therefore overall microbial activity,
equaled rates in the cover-cropped soil, microorganisms present in this
soil metabolized significantly more of the applied acetate. By the end
of the experiment, C cycling characteristics of the cover-cropped soil
were similar to the manure-amended soil; NMR spectra indicated 13C was
incorporated into new SOM in both of these soils. Soil respiration and
13C assimilation rates in the conventional soil remained relatively low.
Microorganisms in the organic soils mineralized and respired more native
C and assimilated more 13C than the conventional soil. Conversely, the
conventional soil mineralized more and assimilated less 13C than the organic
soils. Differences observed in this laboratory experiment may or may not
reflect on C cycling occurring in the field.