Agriculture Reference
In-Depth Information
The potential for groundwater contamination by nitrate from intensive
agriculture is well known (Oren et al., 2004; Vazquez et al., 2006; Thomp-
son et al., 2007). Two main approaches are often used for characterizing
nitrate leaching from agricultural fi elds: (1) characterization of the chemical
composition of the soil pore water in shallow depths under the root zone,
as may be obtained by application suction lysimeters or sediment samples
(Feaga et al., 2010), and (2) determining the cumulative long-term impact on
groundwater as may be obtained from the chemical composition of well wa-
ter (Harter et al., 2002). Apparently, the chemical characteristics of the root
zone pore water may vary dramatically in timescales of days to seasons, ac-
cording to irrigation patterns, fertilizer applications and crop-growing phas-
es. However, the cumulative impact on groundwater develops in timescales
of years to decades. The time lag between the initiations of a contamina-
tion event near the land surface to its detection in the aquifer water depends
on the mechanisms controlling fl ow and transport in the vadose zone. The
ability to characterize fl ow and transport processes in the vadose zone was
recently improved following the development of a vadose zone monitoring
system (VMS) that provides realtime, in situ information on the hydraulic
and chemical state of the percolating water across the entire vadose zone.
Up to now, the VMS has been implemented in a variety of hydrological set-
ups, including (1) fl ood water percolation (Dahan et al., 2007, 2008; Amiaz
et al., 2011), (2) rain water percolation through thick unsaturated sand and
clay formations (Rimon et al., 2007, 2011b; Baram et al., 2012a), and (3)
solute transport in the vadose zone (Dahan et al., 2009; Rimon et al., 2011a;
Baram et al., 2012b).
A newly established agricultural area that has recently been modifi ed
from non-intensive open fi eld agriculture to intensive organic and con-
ventional agriculture in greenhouses provided a unique opportunity to in-
vestigate the contamination potential of these two agricultural regimes.
As such, the main objective of the study was to compare the groundwa-
ter pollution potential of organic versus conventional greenhouses as it is
expressed through the downleaching of nitrate through the vadose zone
underlying these farms. The study was conducted using VMSs that al-
lowed in situ monitoring of the unsaturated zone under selected organic
and conventional greenhouses.
