Agriculture Reference
In-Depth Information
Chapter 10
D
YNAMICS OF
T
OTAL AND
H
UMIC
C
ARBON IN A
L
ONG
-T
ERM
F
IELD
E
XPERIMENT
D
ETERMINED BY
13
C
N
ATURAL
A
BUNDANCE
Paola Gioacchini
1
, Daniela Montecchio,
Ornella Francioso and Claudio Ciavatta
Dipartimento di Scienze e Tecnologie Agroambientali,
Alma Mater Studiorum
Università
di Bologna, viale Fanin 40, Bologna I-40127, Italy
A
BSTRACT
Soil organic carbon (C) preservation in agroecosystems is crucial point to maintain
soil fertility and productivity, and to reduce losses of CO
2
in the atmosphere. Agricultural
management practices can differently affect the level of soil organic C (SOC). In the
present paper or chapter the results of a long-term field experiment (30 years) were
investigated to evaluate the effect of mineral fertilization and organic amendments on soil
organic C content and on the humic acids (HA) that represent the most important and
stable reservoir of soil organic C. The effect of the plant species was also evaluated by
comparing wheat and corn monocultures. The amount of corn-derived C in soil and HA
at the end of the experiment was calculated by
13
C natural abundance measurements.
After 30 years of cultivation, the SOC significantly decreased in both unfertilized
(Control) cropping systems, especially with continuous corn. Mineral fertilization (Min)
and organic amendments (Org) always caused an increase in SOC, especially with Org
treatment on continuous corn. The C always increased in HA, except in the unfertilized
plots of corn monoculture. Again the highest increase was observed with Org treatment.
The amount of corn-derived C in total organic C (TOC) increased in the following order:
unfertilized < Min < Org treatments, ranging from 19 to 29%. The turnover time of the
older C
3
-derived C increased in the same order ranging between 55 and 86 years in the
Control and Org treatment, respectively. In the HA the proportion of corn-derived C was
similar in the Control and Org treatment (26.4%), lower in the Min treatment (23.7%).
Nevertheless if we consider the total amount of corn-derived C in soil and the proportion
recovered in the HA, the highest was measured in the unfertilized control. In general a
1
Corresponding authore: mail address: paola.gioacchini@unibo.it.
