Implications of Soil Biodiversity for Sustainable Organic Matter Management - Sustainable Management of Soil Organic Matter - page 359

in decomposition are due to a higher functionality in the 'DOK' field trial
soils was tested by applying a community-level approach first described by
Garland and Mills (1991) using BIOLOG™ microplates. Patterns of
substrate utilization differed significantly between soils of conventional and
organic farming systems in spring but not in autumn samples (Fließbach
and Mäder, 1997). A functional diversity index obtained from the substrate
utilization patterns of spring samples in winter wheat plots showed higher
values in BIODYN soils than in conventional soils (Table 5.2.3), indicating
a higher potential of catabolic capabilities.
With respect to a functional ecological approach, we combined the
holistic soil biological parameter q CO 2 and the diversity of utilized sub-
strates. Among the soils of the 'DOK' field experiment we found a signifi-
cant inverse relationship of q CO 2 and functional diversity (Fig. 5.2.2). With
increasing functional diversity, the energy needed to maintain the level of
microbial biomass became less, indicating a resource utilization more effi-
cient with respect to microbial growth, and a greater complexity of the
microbial food web. Combining holistic soil functions with
community-level analysis may provide useful tools for interpretation of
soil quality and soil as a microbial habitat.

Conclusions

Even though total soil organic matter differs between organic and
conventional agricultural systems, no substantial changes in the chemical
composition as determined by solid state 13 C-NMR were detectable.
Obviously, the carbon content of the soils was too low and quality changes
in the active pool of SOM too small for a sensitive detection of differences
with this technique.
Labile soil organic matter pools (soil microbial biomass, light fraction
particulate organic matter) indicated distinct changes in soil organic matter

Table 5.2.3. Soil microbial biomass (C mic ), C mic :C org ratio, qCO 2 and functional diversity as
Shannon index. Figures are the mean of four field replicates and are composed of samples from
March 1995 and 1996 (Tukey's test results for manured systems only).

C mic C mic :C org

(mg g − 1 )

qCO 2 Shannon

(H) ( µ g g − 1 ) ( µ g CO 2 -C mg − 1 C mic )

BIODYN 355 a 2.20 a 0.795 a 1.792 a

BIOORG 271 b 1.91 b 1.132 b 1.778 a,b

CONFYM 231 c 1.63 c 1.173 b 1.756 b

185 c 1.35 c 1.364 b 1.798 b

CONMIN

NOFERT 214 c 1.56 c 1.205 b 1.803 ab