In addition, the cropping system allows for maintaining a roughly high level of
OM, mainly by virtuous release by cardoon roots decay at the end of every production cycle. Nevertheless, in soil with higher mineralisation (e.g. with lower
content of clay and/or carbonates), the supply of appropriate compost amounts is
necessary to maintain, or at least to minimise, SOMS losses. Indeed, an exogenous
SOM supply increases biogenic C mineralisation, as well as pool of recalcitrant C in
soil [13]. Therefore, compost amounts need to be appropriate also because the
supply of excessive amounts of compost, i.e. 30 t/ha dry matter in Mediterranean
condition, declines the C conversion efficiency [20], and some threats might occur
(i.e. metals and excess nutrients into groundwater and increase in soil salinity)
depending on compost quality [21].
SOC sequestrations or depletions can be fundamental in greenhouse gases
(GHG) crop management as demonstrated by the Life Cycle Assessment focused
on cardoon agricultural phase.
The GHG balance of one year for cardoon cultivation is reported in Fig. 2.
Among the cardoon cultivation inputs, the main C footprint were due to the
chemical fertilizers (i.e. urea) and diesel according to Cocco et al. [22]. Moreover,
the use of compost cut down on N 2 O emissions according to Aguilera et al. [23].
However, the contribution of SOMS dynamic is preponderant. Carbon source and
sink from soils play a fundamental role in C footprint assessment of agricultural
phase: the net balance of GHG emissions in the “no compost” scenario accounts for
1710 kg CO 2 eq per hectare, whereas the same crop system where compost was
applied resulted to be characterised by 490 kg CO 2 eq per hectare, with an over 70%
reduction.
The promoting of a sustainable agriculture has a huge relevance since agricultural sector represents the ground of bio-economy. High quality compost availability, even assuming a notable increase of bio waste recycling (i.e. 60 million of
metric tonnes per year of bio waste) would result much lower if compared to
potential demand: according to a rough estimation of the authors, the annual
amount of compost (potentially) produced would be enough to be used in the 1–3%
of the EU-28 agricultural land. Consequently, SOM management shall be pursued
with the aim of innovative agricultural practices (e.g. intercropping, green manure,
incorporation of higher amount of biomass in soil etc.). Nevertheless, the authors
agree to the EU Landfill Directive proposal that will oblige EU Member States to
introduce the separate collection of bio-waste as far as is technically, ecologically
and economically feasible. This change, in fact, would activate a series of virtuous
mechanisms whose benefits can be summarise as follows:
1. 10% landfill target achievement and reduction of GHG emissions from inappropriate disposal (i.e. landfill)
2. Increase labour market (i.e. food waste management and composting)
3. Reduction of greenhouse gas emissions from crops cultivation (i.e. CO 2 uptake
linked to SOM increase, Fig. 2)
4. Sustainable agriculture (i.e. no SOM depletion).
138
F. Razza et al.
OM, mainly by virtuous release by cardoon roots decay at the end of every production cycle. Nevertheless, in soil with higher mineralisation (e.g. with lower
content of clay and/or carbonates), the supply of appropriate compost amounts is
necessary to maintain, or at least to minimise, SOMS losses. Indeed, an exogenous
SOM supply increases biogenic C mineralisation, as well as pool of recalcitrant C in
soil [13]. Therefore, compost amounts need to be appropriate also because the
supply of excessive amounts of compost, i.e. 30 t/ha dry matter in Mediterranean
condition, declines the C conversion efficiency [20], and some threats might occur
(i.e. metals and excess nutrients into groundwater and increase in soil salinity)
depending on compost quality [21].
SOC sequestrations or depletions can be fundamental in greenhouse gases
(GHG) crop management as demonstrated by the Life Cycle Assessment focused
on cardoon agricultural phase.
The GHG balance of one year for cardoon cultivation is reported in Fig. 2.
Among the cardoon cultivation inputs, the main C footprint were due to the
chemical fertilizers (i.e. urea) and diesel according to Cocco et al. [22]. Moreover,
the use of compost cut down on N 2 O emissions according to Aguilera et al. [23].
However, the contribution of SOMS dynamic is preponderant. Carbon source and
sink from soils play a fundamental role in C footprint assessment of agricultural
phase: the net balance of GHG emissions in the “no compost” scenario accounts for
1710 kg CO 2 eq per hectare, whereas the same crop system where compost was
applied resulted to be characterised by 490 kg CO 2 eq per hectare, with an over 70%
reduction.
The promoting of a sustainable agriculture has a huge relevance since agricultural sector represents the ground of bio-economy. High quality compost availability, even assuming a notable increase of bio waste recycling (i.e. 60 million of
metric tonnes per year of bio waste) would result much lower if compared to
potential demand: according to a rough estimation of the authors, the annual
amount of compost (potentially) produced would be enough to be used in the 1–3%
of the EU-28 agricultural land. Consequently, SOM management shall be pursued
with the aim of innovative agricultural practices (e.g. intercropping, green manure,
incorporation of higher amount of biomass in soil etc.). Nevertheless, the authors
agree to the EU Landfill Directive proposal that will oblige EU Member States to
introduce the separate collection of bio-waste as far as is technically, ecologically
and economically feasible. This change, in fact, would activate a series of virtuous
mechanisms whose benefits can be summarise as follows:
1. 10% landfill target achievement and reduction of GHG emissions from inappropriate disposal (i.e. landfill)
2. Increase labour market (i.e. food waste management and composting)
3. Reduction of greenhouse gas emissions from crops cultivation (i.e. CO 2 uptake
linked to SOM increase, Fig. 2)
4. Sustainable agriculture (i.e. no SOM depletion).
138
F. Razza et al.