Implications of Soil Biodiversity for Sustainable Organic Matter Management - Sustainable Management of Soil Organic Matter - page 358

(C LF , i.e. the microbial substrate) serves as an indicator of the catabolic
potential of the soil microbial community (Table 5.2.2).
The catabolic potential of soil microorganisms is important with
respect to the decomposition of the organic residues. In an incubation
experiment with 14 C-labelled plant material, mineralization ( 14 CO 2 ) and
microbial incorporation ( 14 C mic ) were followed over 6 months. In BIODYN
soils, the total metabolized material ( 14 CO 2 + 14 C mic ) was > 10% higher
than in the compared conventional and unmanured soils (Fließbach et al .,
2000) (Table 5.2.2). This suggests a more complete decomposition of the
applied material and finds an equivalent in the above-mentioned quotient
of microbial biomass to light fraction C. The hypothesis that the differences

Fig. 5.2.1. 13 C CP MAS NMR spectra of whole soil samples pre-treated with hydrofluoric acid
(each line represents the mean of the four field replicates).

Table 5.2.2. Quotient of microbial biomass and light fraction organic matter (C mic :C LF ) and the
percentage of the applied labelled plant material mineralized ( 14 CO 2 ) and microbially assimilated
( 14 C mic ). Figures are the mean of four field replicates (different letters indicate significant
differences, P< 0.05).

% 14 C metabolized

C mic :C LF (mg g − 1 )

14 CO 2 14 C mic 14 CO 2 + 14 C mic

BIODYN

a 2.27 a a 63.3 a a 9.4 a a 72.7 a

BIOORG

a,b 1.54 a,b

ND ND ND

CONFYM

cb 1.13 bc b 56.7 b b 5.6 b b 63.3 b

CONMIN

a 0.64 c b 55.1 b b 5.4 b b 60.5 b

cb 0.70 bc b 54.7 b b 6.6 b b 61.3 b

NOFERT