Page 14 - Read online

Page 10 of 19 Maffia et al. Carbon Footprints 2026, 5, 7

Figure 2. Unit forming colonies per gram of dry soil of fungi, bacteria, and actinomycetes in soil at the initial state (CTR0), untreated soil
(CTR), soil treated with compost (C), vermicompost (V), digestate (D), and sulfur bentonite with olive pomace (SBO). Data are the mean
of three replications ± standard deviation. Different letters indicate statistically significant differences among the treatments according to
Tukey’s test (P < 0.05).

Table 3. Number of fungi, bacteria and actinomycetes in relation to the total microbial biomass C in soil at the initial state (CTR0),
untreated soil (CTR), and soil treated with compost (C), vermicompost (V), digestate (D) and sulfur bentonite with olive pomace
(SBO)
% % % FBC BBC ABC
Fungi/MBC Bacteria /MBC Actinomycetes/MBC
b
b
CTR0 20.9 ± 0.9 41.9 ± 1.4 37.2 ± 0.9 188.2 ± 8 376.3 ± 8 334.5 ± 5
d
a
d
b
CTR 21.7 ± 0.8 43.5 ± 1.2 34.8 ± 0.8 171.6 ± 9 343.1 ± 5 274.3 ± 7
d
c
a
b
d
c
C 27.1 ± 1.1 40.5 ± 0.9 32.4 ± 0.6 293.6 ± 7 440.4 ± 9 353.0 ± 8
c
a
b
a
c
c
V 28.2 ± 0.9 45.1 ± 1.5 26.8 ± 0.8 281.5 ± 6 450.2 ± 7 267.3 ± 9
d
a
c
cd
c
a
b
d
d
D 32.8 ± 1.3 40.3 ± 1.1 26.9 ± 1 314.5 ± 8 385.9 ± 7 257.6 ± 6
b
b
b
SBO 40.0 ± 1.2 33.9 ± 1 26.2 ± 0.9 372.8 ± 5 315.5 ± 8 243.7 ± 5
a
a
d
c
e
d
Fungi Biomass C (FBC, µg C g ); Bacteria Biomass C (BBC, µg C g ); Actinomycete Biomass C (ABC, µg C g ). Data are the means of three
-1
-1
-1
replicates ± standard deviation. Different superscript letters within the same row indicate significant differences among treatments according to
Tukey’s Honestly Significant Difference (HSD) test (P < 0.05). MBC: Microbial biomass carbon.
Considering the percentage of fungi, bacteria, and actinomycetes with respect to the total MBC and for each
treatment, SBO was the treatment that mostly increased the amount of fungi, vermicompost mostly
increased the bacteria percentage unexpectedly, and the actinomycetes were decreased by treatments
compared to the control 0. The Fungi biomass expressed as microgram C per gram of soil was increased by
SBO, and the ranking was SBO > D > C > V > CTR0 > CTR. The highest amount of bacterial biomass was
detected in vermicompost and compost. Actinomycetes were the greatest in soil treated with compost [Table
3].