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| Titel |
Reclaimed peatland for agriculture: implications for water and farming management in Mediterranean areas |
| VerfasserIn |
Rudy Rossetto, Paolo Basile, Emilia Cavallaro, Stefano Menichetti, Chiara Pistocchi, Tiziana Sabbatini, Nicola Silvestri, Enrico Bonari |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054501
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| Zusammenfassung |
| During the last century, reclaimed peatland played an important role in increasing farmland
mainly due to the possibility of dewatering wetlands using pumping stations. These wetlands
were generally sustained by the presence of shallow phreatic aquifers, whose water table was,
and it is still today, then lowered by the presence of a dense ditch network. Nevertheless, such
land management leads to environmental problems, of which subsidence undoubtedly is
the greatest problem when attempting to sustain agricultural activities (Andriesse,
1988).
Around the Massaciuccoli Lake (Tuscany, Italy) six peatland areas (Bonifica) of about 32
km2 were reclaimed between 1920 and 1930, after a struggle lasting about 2000 years.
As soon as reclamation started, subsidence began (2 to 3 m in 70 years), leaving
the lake perched and central respect the low drained areas, now 0 to -3 m below
m.s.l., and requiring 16 km embankment construction. Moreover, during the last 40
years eutrophication phenomena arose and it was thought to be due to excess crop
fertilization.
In order to get a deeper insight on such problems, a survey of groundwater and surface
water quality along with hydrological monitoring and agriculture surveys was carried out
in 2008-2009 in the most intensively cultivated reclaimed areas (Pistocchi et al.,
2010).
Results show that peat subsidence may have several serious consequences in farmland
management. Drainage should be now adapted to new levels because pumping stations
cannot reach the required groundwater head for farming (the so-called Devil’s circle for
peatland exploitation) and large pieces of land are already uncultivated. Subsiding areas are
also at high risk of inundation and flooding.
Moreover, areas interested by much severe subsidence shows also notable orthophosphate
values in groundwater, ranging from 5.5 to 0.3 mg/l, being even one order of magnitude
higher than those detected in surface water. We hypothesize that besides a potential
agricultural origin, phosphorous presence in groundwater may be related to peat exposure and
mineralization related to the drainage of waterlogged and anaerobic peat turning, then, to
aerobic conditions (Rossetto et al., 2010). Agricultural practices, such as tillage, may enhance
phosphorous input by increasing organic matter oxidation. As peat soils in the study area
show high organic matter content (up to 40%), mineralized phosphorous quantity, calculated
using annual mineralization rate typical under Mediterranean climate, suggests an important
contribution to groundwater. Phosphorus in groundwater might be then of ecological concern
especially during base flow conditions, when groundwater contributions to surface water
are greatest and are coincident with optimum temperature conditions for primary
production. An increase in carbon dioxide emission is expected also, but no data is still
available.
Options for mitigating these adverse effects caused by subsidence are currently being
evaluated. They are related to changes in the cropping systems, i.e. long term crops (such as
short rotation forestry, forage crops or saturated pasture) or in farming practices (e.g. no or
minimum tillage) in order to reduce mineralisation, and/or to changes in land use. The latter
include options such as shallow flooding (which might also lead to organic matter
accumulation and then reverse subsidence) or deep flooding to create open-water
habitat.
References
Andriesse, J.P. 1988. Nature and Management of Tropical Peat Soils. FAO Soils Bullettin
59, Rome. ISBN 92-5-102657-2
Pistocchi, C., Baneschi, I., Basile, P., Cannavò, S., Guidi, M., Risaliti, R., Rossetto, R.,
Sabbatini, T., Silvestri, N., Bonari, E. 2010. Water quality and agricultural practices: the case
study of southern Massaciuccoli reclaimed land (Tuscany, Italy). Geophysical Research
Abstracts Vol. 12, EGU 2010 Vienna
Rossetto, R., Basile, P., Cavallaro, E., Menichetti,S., Pistocchi, C., Sabbatini, T., Silvestri,
N., Bonari, E. 2010. Phosphorous presence in groundwater from peat oxidation:
preliminary results from the Lake Massaciuccoli area (Italy). Book of Abstracts.
International Groundwater Symposium I.A.H.R. Valencia (Spain) - September 22-24, 2010 |
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