Introduction
Soil, as a control on the biogeochemical and hydrological cycles of the Earth
system and a provider of vital goods and services to sustain life, is one of
our most important natural resources (Berendse et al., 2015; Brevik et al.,
2015; Keesstra et al., 2012). Soil salinisation – a term used to refer
comprehensively to saline, sodic, and alkaline soils (van Beek and Tóth,
2012) – is one of the major soil degradation threats globally, especially in
drylands. In advanced stages salinisation transforms fertile and productive
fields to barren land, thus restraining any vegetation growth (Chesworth,
2008; Jones et al., 2012; Tóth et al., 2008). High levels of soil salt
accumulation can impact agricultural production, environmental health, and
economic welfare (Rengasamy, 2006). Globally, 34 Mha – about 11 % of
total irrigated land – is estimated to be impacted (Montanarella, 2007).
Salinisation is often linked to arid irrigated lands where prevailing low
rainfall, high evapotranspiration rates and soil characteristics impede soil
leaching, thus causing salt to accumulate in the upper layers (Chesworth,
2008; Maas et al., 1999; Mateo-Sagasta and Burke, 2011). While moderate
problems are reported even when irrigating with water of sufficient quality,
constant or increasing soil salinity is chiefly caused by the use of highly
saline irrigation water such as groundwater suffering from seawater intrusion
(Dubois et al., 2011; Geeson et al., 2003; Mateo-Sagasta and Burke, 2011;
Tóth and Li, 2013; van Camp et al., 2004).
Soil salinity is a major factor limiting crop production and land development
in coastal areas (Li et al., 2012; Sparks, 2003) and is a major cause of
desertification in the Mediterranean countries. Along the Mediterranean
coast, the problem of soil salinity is increasing due to scarcity of
precipitation and irrigation with low-quality water. Saline soils here are
present mainly due to human activities (Abu Hammad and Tumeizi, 2012;
Domínguez-Beisiegel et al., 2013), especially with the extension of
irrigation and the unmanaged use of saline water. In the Mediterranean
region, 25 % of irrigated agricultural land is affected by a significant
level of salinisation leading to soil degradation (Geeson et al., 2003;
Mateo-Sagasta and Burke, 2011). Water supply in Greece is largely derived
from groundwater sources, and about 9 % of the approximately 1.4 Mha of
irrigated land is affected by soil salinisation due to seawater intrusion
(Jones et al., 2003; OECD, 2009). Seawater intrusion in most coastal areas of
Greece has progressed a great distance inland, especially in the south, which
is characterised by a more arid climate (Daskalaki and Voudouris, 2008). The
island of Crete (Fig. 1) is no exception to the problem, with intensive
agriculture and high tourism activity being the two prime factors that
strongly impact upon the available water resources. Agricultural growth in
the Messara Plain of Crete has significantly impacted the water resources and
ecosystem services of the area by substantially increasing groundwater demand
(Daliakopoulos and Tsanis, 2014). The problem is exacerbated by poorly
managed or unmanaged groundwater extraction and distribution as well as arid
climatic conditions. Seawater intrusion in the coastal aquifer of Timpaki
(Paritsis, 2005; Vafidis et al., 2013) adversely affects both water resources
and soil.
Areas of seawater intrusion in Greece (left) and specifically in
Crete (right). Adopted from Daskalaki and Voudouris (2008) and
EEA (1999).
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Sustainable land management (SLM) solutions for the problem of soil
salinisation largely depend on water availability, climatic conditions,
period of salinity, land use and type of assets under threat, the current
extent and rate of the threat, and the availability of resources (capital,
inputs). Measures can be applied in conjunction with a wide range of
amelioration methodologies (Ali, 2011; Qadir et al., 2000) which can
nevertheless be very case specific. A brief account of such methodologies
towards soil and water sustainability is presented in Table 2. The adoption
of SLM practices depends on personal, sociocultural, socio-economic,
institutional, and biophysical factors (Illukpitiya and Gopalakrishnan, 2004)
rather than technical ones (Kessler, 2006). The range of variables that
affect adoption may have contrasting effects depending on context (Liu et
al., 2013), and while economic incentives (e.g. Posthumus and Morris, 2010)
and accounting for risks, effectiveness, time, and effort involved in
implementation strongly influence SLM technology adoption (e.g. Sattler and
Nagel, 2010), subjective user preference may be equally or more important
(e.g. Wauters et al., 2010). The World Overview of Conservation Approaches
and Technologies (WOCAT, 2008) global network has been established to assist
SLM specialists and practitioners from all over the world in sharing valuable
knowledge and improving decision-making concerning alternative SLM practices
(Liniger and Critchley, 2007; Schwilch et al., 2011), thus eventually
facilitating SLM adoption. A review of the WOCAT database reveals that 10 out
of 11 documented measures for soil salinity amelioration or adaptation cover
agronomic, vegetative, or management rather than structural measures (WOCAT,
2015). While this is by no means a representative sample, it points to
a preference of the stakeholders for low-cost, decentralised, and self-sustained
solutions. Besides, stakeholder-inclusive decision making against soil
salinity is currently gaining popularity (e.g. Bowmer, 2014; Hornidge et al.,
2011; Lázár et al., 2015; Schultz et al., 2007) around the
world. Through global sharing of successful (or failed) SLM experiences by
researchers, technicians, planners, and end users involved in combating soil
degradation, WOCAT strives to augment efficiency in the application of
knowledge and funds for improved decision making and optimised land
management.
The RECARE (Preventing and Remediating degradation of soils in Europe
through Land Care) FP7 project aims to develop effective prevention,
remediation, and restoration measures using an innovative transdisciplinary
approach, actively integrating and advancing knowledge of stakeholders and
scientists in 17 case studies, covering a range of soil threats in different
biophysical and socio-economic environments across Europe. RECARE uses
WOCAT to identify prevention, remediation, and restoration measures currently
used to combat soil salinisation in Greece (among other soil threats at 16
other European sites). In this context, and towards an interdisciplinary
approach on soil research (Brevik et al., 2015), this work
assesses and discusses a stakeholder involving selection process for the
application of promising technologies for soil salinity amelioration,
focused at greenhouses cultivations of Timpaki, Crete.
Methodology
The WOCAT Technology Questionnaire
The WOCAT Technology Questionnaire (QT) defines SLM technologies as
“agronomic, vegetative, structural and/or management measures that prevent
and control land degradation and enhance productivity in the field”. These
solutions may include mechanical structures (e.g. terraces, check dams,
contour stone walls, and contour ridges), biological structures (e.g.
afforestation and strips of vegetation), manipulation of the surface soil
(e.g. tillage; mulching; and soil amendments such as surfactants, compost, and
animal and green manure), rainwater harvesting (e.g. reservoirs and
retaining dams), agronomic measures (e.g. drought-resistant species and
varieties, short-cycle varieties, crop rotation, animal and green manures,
appropriate fertiliser use, compost, and weed control), and management
measures (e.g. timing and intensity of agricultural activities, grazing
management).
The QT describes case studies from the field and is always linked to a
specific area where the technology is applied and to SLM specialists who
provide the information. It addresses the specifications of the technology
(purpose, classification, design, and costs) and the natural and human
environment where it is used. It also includes an analysis of the benefits,
advantages and disadvantages, economic impacts, acceptance, and adoption of
the technology (Schwilch et al., 2009). The collection of information
involves personal contacts and knowledge sharing between land users and SLM
specialists. The immediate benefits of filling in the questionnaires include
the compilation of fragmented information – often consisting of the
undocumented experiences of land users and specialists – and a sound
evaluation of one's own SLM activities (Liniger and Schwilch, 2002) so that
they can be retrieved and suggested under similar biophysical, socio-economic,
and institutional conditions.
Stakeholder interaction
The stakeholder interaction methodology presented here starts with a
participatory identification of actual and potential prevention, remediation,
and restoration measures during a stakeholder workshop where a first
selection of promising measures is made. At this workshop, participating
scientists also propose soil salinisation prevention/amelioration measures
documented in the literature (adopted to the case study conditions) to
ensure sufficiently sound alternatives are available, while stakeholders
provided measures form their personal experience. Feasible and promising
measures are singled out during the workshop, and WOCAT questionnaires for
SLM technologies are used to document them. Knowledge gaps and ambiguities
are clarified via personal communications with experts.
At a subsequent workshop documented technologies are presented in depth and
a list of possible local and scientific criteria are identified in
collaboration with stakeholders. Criteria are grouped by the technology's
benefit or impact categories, as depicted by WOCAT: (a) production and
socio-economic, (b) sociocultural, (c) ecological, and (d) off-site
benefits. Eventually, criteria of each category are ranked from the least to
the most important according to stakeholder perception. Prominent
technologies are also assigned scores per criterion for their expected
effects on reducing soil degradation, related costs and benefits, and ecosystem
services, also reflecting the degree to which these technologies are
acceptable by stakeholders.
Technology evaluation and selection
A simplified version of the multi-criteria analysis (MCA) described in
Mendoza et al. (2000) is used for the evaluation of each technology t
considering a set of criteria c which, under the premise of the previous
paragraph, fall within a single criteria category. Considering that criteria
are ranked in ascending order of importance (i.e. 1 is the least important
and n is the most important of n number of criteria), weights
(Wc) can be assigned so that ∑c=1nWc=1. Per criterion, a technology is assigned a score
(Sc,t) which is taken into account weighted by Wc
to estimate the cumulative score St, such that
St=∑c=1nWc×Sc,t.
The result of this weighting allows technologies to be ranked per benefit
category, assuming that categories themselves cannot be directly compared. For
example, here we consider that, e.g., off-site benefits cannot be measured
against sociocultural benefits, so a unique St is calculated per
benefit category. In an effort for parsimony, here we ignore several aspects
of decision analysis uncertainty (Scholten et al., 2015).
Case study
The Timpaki Basin is connected to the western Messara Plain by the
Geropotamos River through the Phaistos Gorge and encompasses an area of
50 km2 located in the central-south area of Crete with a mean elevation
of 200 m. The topography of the basin is generally flat with steeper slopes
in the northeast, with the highest point being part of the Psiloritis Mountain
(Fig. 1). The climate ranges between sub-humid Mediterranean and semi-arid
with mild moist winters (average temperature: 12 ∘C) and dry hot
summers (average temperature: 23 ∘C), while the mean annual
precipitation is around 500 mm. As there is little surface water flow
outside the winter months (Vardavas et al., 1997), groundwater is the main
source of irrigation water and the key resource controlling the economic
development of the region. Water shortage often occurs, due to temporal and
spatial variations of precipitation, increased water demand during summer
months, and the difficulty of transporting water due to the mountainous areas.
Lately, there have been growing concerns over the possible depletion or
deterioration of the groundwater quality due to intensive pumping beyond the
safe yield of the basin (Tsanis and Apostolaki, 2008) and the gradual
seawater intrusion (Paritsis, 2005; Vafidis et al., 2013). Despite measures
for the protection of water resources imposed by the local water authority
since 1984, implementation has faced difficulties mainly due to private wells
(Kritsotakis and Tsanis, 2009).
Because of the favourable climatic conditions year-round, Timpaki is a highly
exploited area concerning the greenhouse cultivations, even compared to the
parent municipality of Phaistos (Table 1). Horticultural crops are
drip-irrigated almost exclusively from groundwater extraction; harvested
twice a year; and mainly comprised of tomato (Solanum lycopersicum),
cucumber (Cucumis sativus), zucchini (Cucurbita pepo),
eggplant (Solanum melongena), pepper (Capsicum annuum), and
green beans (Phaseolus vulgaris) (Thanopoulos et al., 2008). Here we
address only tomato, the prevailing and most profitable horticultural crop
under plastic. Tomato is moderately sensitive to salinity, able to withstand
soil electrical conductivity (EC) up to 2.5 dS m-1 without significant
yield losses (∼ 10 %) but suffering a 50 % yield loss at
5.0 dS m-1 (Jones Jr., 2007).
Left, population in Timpaki (Source: HSA, 2015); right,
“real GDP growth rate – volume – percentage change on previous year” for
the Euro area, Greece, and Crete (Source: EUROSTAT, 2015; HAS,
2015).
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Units in ha (% of total). Source: HSA (2008).
Area
Olive trees
Arable crops*
Horticulture
Citrus
Vine trees
Total
Timpaki
1100 (43 %)
1005 (39 %)
401.5 (16 %)
37 (1 %)
3 (0 %)
2540.2
Phaistos
13 090 (79 %)
1805 (11 %)
1404.3 (8 %)
187.5 (1 %)
62.4 (0 %)
16 549.2
* Major arable crops include watermelons, melon, and potatoes.
Contrary to many rural areas in Greece that face the effects of urbanisation,
the population of Timpaki has been steadily rising since the 1950s, mainly due
to the opportunities offered by the tourism sector in this coastal area
(Fig. 2, left). Furthermore, there is evidence that suggests a motion of rural
repopulation may have been activated in the country (Gkartzios and Scott,
2015). In Timpaki, land is mostly privately owned, and water rights can be
public, cooperative, or private. The socio-economic gap among farmers is not
too wide and more or less on par with those of the rest of the community
which has faced a prolonged crisis leading to little overall investments and
financial contraction (Fig. 2, right). Stakeholders often hold more than one
role in the community, which often facilitates confrontation, either
perpetuating or forcing conflicts to be resolved.
List of amelioration technologies for soil salinisation.
Technology
SLM category1
Main benefits2
Selected references
Leaching (provided good drainage conditions)
A
A7
Ali (2011), Qadir et al. (2000)
Surface flashing
A
A7
Qadir et al. (2000)
Drip irrigation
S, A
A1, A8
Ali (2011), Wan et al. (2007)
Watering at night
M
A1, A8
empirical
Increase of irrigation water every 3–4 watering events
A, M
A7
empirical
Irrigation with saline water at less sensitive growth stages
A
A4
Ali (2011)
Mixing of saline and non-saline water
M, A, S
A5,
Ali (2011), Malash et al. (2005)
Alternate/cyclic irrigation with saline and freshwater
A, S
A4
Ali (2011)
Alternative water resources (e.g. reuse of wastewater) (e.g. T1)
S, M
A5
Ali, (2011), Iannetta andColonna (2009)
Desalination of irrigation water
S, M
A5
Iannetta and Colonna (2009)
Mechanical removal of salt surface salt crust
A, S
A7
Ali (2011), Qadir et al. (2000)
Careful use of machinery (no heavy machinery)
M
A2, A3
Iannetta and Colonna (2009)
Green manuring – mulching with manure (e.g. T2)
A
A2, A3
Ali, (2011),Chatzigiannakis et al. (2012)
Use of compost or other organic soil amendments
A, M
A1, A3
Chatzigiannakis et al. (2012), Oo et al. (2015),Srivastava et al. (2014)
Mulching with leaves/bark or other material
S, A
A1, A7
Al-Dhuhli et al. (2010),Ali (2011), Mao et al. (2014)
Use of inorganic amendments (e.g. Si, CaSO42H2O, H2SO4)
A
A3, A4, A8
Ahmad et al. (2013),Matichenkov andKosobrukhov (2004)
Biological reduction (phytoremediation or bioremediation)
A, V, M
A4
Ahmad et al. (2013), Ashraf et al. (2010), Qadir et al. (2007) Singh et al. (2015)
Introduction of salinity- and hypoxia-tolerant plants
M, V
A1, A3, A7
Ali (2011), Qadir et al. (2000)
Land use change from irrigated to rainfed
M, V, A
A5
Iannetta and Colonna (2009)
Implementation of drainage systems
S
A2, A7
Ali (2011),Chatzigiannakis et al. (2012)
Intervention to the nutrition of plants (e.g. fertilisers)
A
A4
Flores et al. (2004),NavarroPedreno et al. (1996)
Drought pre-treatment of seedlings or seeds with NaCl
A
A4
Cayuela et al. (2007)
Grafting seedling on proper rootstock
A
A4
Estañ et al. (2005),Fernández-García et al. (2004)
Inoculation with mycorrhizal associations (e.g. T3)
A
A4
Copeman et al. (1996)
Bio-priming with biological agents (e.g. T3)
A
A4
Rawat et al. (2011)
Pre-sowing (or pre-plant) irrigation
A, M
A4
Ali (2011)
A: agronomic; M: management; S: structural; V: vegetative; T1, T2, and T3 are
explained in the text. 1 SLM measure category after WOCAT.
2 As explained in Table 3.
Participatory selection of SLM technologies
In the context of the RECARE project, Timpaki has been selected as a case
study of the salinisation soil threat. As part of the stakeholder
participation and valuation activities, 20 local and external stakeholders
(including local and prefectural administrative authorities, agricultural
technicians, farmers, scientists, and NGO representatives) participated in a
local workshop in February 2015. Stakeholders were asked to (1) identify and
group the primary constraints of greenhouse production linked to soil
salinisation and to (2) discuss the list of potential technologies for addressing
the soil salinisation threat from a user's point of view and select the most
promising technologies currently applied. Criteria for selection included
compatibility with current agricultural practices as well as sustainable
investment and maintenance cost.
At a second workshop, stakeholders were invited to (1) assess promising
technologies using criteria from the WOCAT QT and (2) reach a consensus
regarding the perceived ranking of criteria of the same category. Through
this process, promising technologies were assessed and selected using a
participatory approach that combines collective learning with the application
of a globally standardised documentation and evaluation framework as well as
follow-up communication with experts. Table 2 presents a comprehensive list
of empirical and literature prevention and amelioration technologies that
have been applied to combat the soil salinisation threat, along with a
representative reference. Table 2 also lists the type of measure according to
WOCAT classification as well as the main prevention/amelioration strategy
addressed by the respective technology (explained in Table 3). The next
paragraphs thoroughly discuss the three most prominent technologies that
surfaced from the participatory selection of the technologies listed in
Table 2. These technologies were selected among already-applied approaches
that were unanimously considered by stakeholders as “best practices” for
greenhouse cultivation in the area.
Intervention strategies of salinisation amelioration technologies.
Symbol*
Measure goal
A1
Decrease of evaporation – conserve soil water content
A2
Increase drainage
A3
Improve of soil quality structure
A4
Adaptation: increase of plants saltresistance or decrease of plants saltaccumulation
A5
Improve irrigation water quality
A6
Depression of groundwater table
A7
Decrease soil salt accumulation
A8
Reduce irrigation water application
* As used in Table 2.
Technology 1 (T1): rainwater harvesting from greenhouse roofs
Rainwater harvesting is one of the most ancient soil and water conservation
and management technologies (AbdelKhaleq and Alhaj Ahmed, 2007).
Nevertheless, applications are still current, often taking advantage of
greenhouse structures (Islam et al., 2013; Ji et al., 2010) and explicitly
practiced against soil salinity in greenhouses (Davies et al., 2011). The
technology involves taking advantage of greenhouse roofs used as catchment
areas for rainwater harvesting. Harvested rainwater is used for irrigation,
either on its own or mixed with water from other sources. A network of
gutters is installed to channel water into a storage tank that can be either
above ground or at ground level, open or covered (Fig. 3). Reservoir size may
be determined by various criteria, but the rule of thumb in the area is to
construct 300 m3 ha-1 of greenhouse area. A cover may also be
installed to reduce evaporation. Furthermore, a suitable pump and mixing
facilities are installed to control water quality and quantity. During
operation, a water filter and/or other water treatment may be required for
removal of particles and waterborne-disease mitigation.
A network of gutters (a) channels rainwater into a reservoir
facility (b) that can be optionally covered (c). The stored water is then
pumped (d) into a mixing tank (e) where it dilutes the saline groundwater
pumped from the aquifer (f). Reduced-salinity water is then directed to the
irrigation system (g) of the greenhouse.
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The technology promotes sustainable land management through prevention and
mitigation of land degradation by increasing water resource
self-sufficiency, thus allowing the user to rely less on the scarce
groundwater resources and reducing the risk of soil salinisation and
production failure. Furthermore, the technology improves the overall
irrigation water quality, both on- and off-site. The main disadvantage of the
technology, especially for the cultivation of tomatoes, which require
irrigation water of moderate electric conductivity, is the increase of
compensating agricultural inputs (i.e. fertilisers). This disadvantage can be
mitigated by mixing freshwater with water from lower-quality sources (e.g.
Malash et al., 2005). The technology requires average technical knowledge
from both the agricultural advisor and the land user. Establishment costs
include the construction of the preparation of the tank placement surface,
the tank construction, the installation of the gutter network, and the
installation of the pump and water sanitation measures. The majority of the
greenhouses in the region have built-in gutters between the basic
construction units in order to discharge rainwater from the roof for
structural safety. Thus, few additional structural measures are required
besides the construction of a reservoir system, such as a PVC-lined
aboveground tank or artificial pond. Maintenance costs of the gutter network,
the water storage tank, and the pump are negligible. Total costs amount to
approximately EUR 14 000 ha-1 for a water storage that can
cover at least 50 % of the irrigation demand throughout the year, but this can
vary depending on scale.
Technology 2 (T2): crop rotation for green manuring in
greenhouse
Green manuring is also part of our global heritage of ancient agricultural
practices (MacRae and Mehuys, 1985) and has been regaining attention as an
organic farming soil amendment. The positive effects of green manuring on
open-field vegetables are well documented (Beckmann, 1977; Chaves et al.,
2004; MacRae and Mehuys, 1985; Stirling and Stirling, 2003;
Thorup-Kristensen, 2006) and followed by modern greenhouse applications
(Aghili et al., 2014; Duyar et al., 2008; Rose et al., 2015; Tüzel et
al., 2013). Here, the angiosperm Sorghum vulgare used in greenhouse
cultivations is suggested as green manure through crop rotation with tomato
plants. The crop rotation usually takes place every other summer when local
greenhouses remain otherwise fallow. Initially, when the main crop (tomatoes)
is removed from the greenhouse in May/June, about 70 kg ha-1 of
sorghum seeds are sown and incorporated into the soil by ploughing at about
4–5 cm depth. Sorghum is drought- and heat-tolerant as well as moderately
salt-tolerant (Netondo et al., 2004); thus the irrigation needs are minimal
and depend on the respective climatic conditions. Water stress conditions may
adversely affect grain production but promote root system expansion; thus
improving soil structure is in this case favourable. Before the beginning of
the tomato season in September, the farmer uses a branch grinder to fritter
the sorghum plants and then incorporates them into the soil by tillage
(Fig. 4). At this time the sorghum is still at a soft dough stage (Vanderlip,
1993), so a 20 cm deep tillage is enough to dispatch the rooting system, and
immature grains will not grow back in the greenhouse. The process also needs to
be well scheduled to provide enough time for greenhouse sanitation before
planting tomatoes.
Sorghum rotation, from seeded in May to incorporation in the soil
in August using a tiller.
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The technology is applied as an effective agronomic measure for the increase
of soil productive capacity, the reduction of pests and soil-borne parasites
such as nematodes (Gardiano et al., 2014; Ortiz et al., 2015), and the
mitigation of soil salinity (Netondo et al., 2004). This technology mitigates
and prevents soil degradation by improving the soil and subsoil structure
through the deep root system of sorghum (often > 1 m for mature
crops) and increasing nutrient and organic matter availability through the
incorporation of the plant biomass into the soil by tilling it under.
Furthermore, organic amendments favour soil hydrology and structure
(Yazdanpanah et al., 2016), thus mitigating salt accumulation in the root
zone. The technology requires little technical knowledge from both the
agricultural advisor and the land user. The increase of workload and the
demand of irrigation water during the dry summer period constitute the main
drawbacks of this technology. Otherwise, it has negligible establishment
costs in the sense that it can be part of the usual farming practices but
requires maintenance and recurrent activity costs such as seed and sowing
costs, irrigation, and machine hours for reducing branch length with a branch
grinder and incorporating sorghum into the soil with a tiller, which can
amount to EUR 1000 ha-1 every 2 years mainly due to labour (i.e.
for small-scale farmers personal effort is usually sufficient for the
application of the technology, and the only cost is that of seeds and machine
rental, or about EUR 200 ha-1).
Technology 3 (T3): application of biological agents to increase crop
resistance to salinity
The Trichoderma ssp. fungus and various types of symbiotic associations
of mycorrhizae are used in greenhouse cultivations in order to mitigate the
impacts of salinity on crops and to improve existing soil properties. These
biological agents are supplied commercially as soil amendments, and specific
treatments vary according to cultivation type. The implementation of
biological agents usually takes place once per plant as the microorganisms
coexist with the plant (symbiotic association) and can be performed in
different stages of the crop cultivation, depending on the commercial product,
e.g. as a solution in the irrigation water; as a solid soil amendment in the
early growing stages (Fig. 5); or, optimally, at the plant nursery (seed
bio-priming) or during planting (plant inoculation). Biological agents
require increased organic matter in the soil; absence of toxic substances
(e.g. copper, fungicides, and pesticides); and, depending on agent type,
suitable soil moisture and temperature. Here we investigate the effects of
biological agents in tomato plantations, which are implemented in the early
growing stages through irrigation.
Mycorrhiza supplement in the form of grey aggregates used during tomato transplantation.
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The technology is applied as an effective agronomic measure for the increase
of plants' salt tolerance, the reduction of soil-borne diseases that affect
plant roots, and increase of water and nutrient absorption. This technology
prevents or mitigates soil degradation by improving the subsoil structure by
causing plant root system expansion and increase of the ability of the plant
to absorb phosphates and micronutrients (Altomare et al., 1999). This effect
can potentially decrease agricultural inputs (water and fertilisers) up to
40 %. An additional benefit is the maintenance and increase of subsoil
fauna diversity and the subsequent biodegradation. The improved soil
structure promotes higher infiltration rates, mitigates the salt accumulation
in the root zone, and combats soil salinity, one of the main soil degradation
problems in the coastal zone. Finally, the application of biological agents
helps to keep the plants healthy, thus leading to increased crop yield and
reduced production risk. The technology requires high technical knowledge
on the part of the agricultural advisor but little from the side of the
land user. The technology has negligible establishment costs since it can be
part of the usual farming practices but requires the recurrent activity costs
of inoculation with the selected biological agent. For an annual application
of a biological agent the total cost is on average EUR 3000 ha-1 year-1
depending on expert advice.
Results and discussion
Technology evaluation
A first interpretation of results (Table 4) shows that T1 is the only
technology that directly contributes to the reduction of soil salinity,
whereas T2 and T3 have an indirect effect but also act as soil amendments,
thus enhancing other soil functions in the process. Due to the immediate
effect of freshwater application, it is safe to say that rainwater harvesting
(T1) is the scientifically and ecologically optimal solution for conditions
of extremely saline soil, whereas T2 and T3 do require some levels of soil
fertility in order to produce results. The use of rainwater harvesting (T1)
provides a degree of water autonomy, thus providing farmers with a sense of
security for optimising or diversifying production. Additional value is
derived by conflict mitigation within the community through the off-site
benefit of overall increase of water availability. Disadvantages include soil
sealing of fertile soil, thus reducing cultivated space, and the contingency
on climatic conditions (precipitation/evaporation). Nevertheless, the latter
is minor since during dry years the storage tank can be used as a basic buffer
for other sources of water, and the application of covers, shading solutions
(Hassan et al., 2015), or wind shelters (Hipsey and Sivapalan, 2003) can
reduce evaporation. The significant reservoir installation cost and
accommodation are the limiting factors and indeed the largest deterrent,
especially for small-property owners. The economic feasibility of rainwater
harvesting for irrigation has also been investigated by Liang and van
Dijk (2011), who highlighted the importance of low pricing of groundwater that
can render the investment in small and medium rainwater-harvesting systems
less attractive. Under the current circumstances, the net profit from this
investment may be positive only for large-property owners or after long-term
use. It is estimated that only 5 % of land users in the area own a
water-harvesting system and about 70 % have constructed it using external
material support. Nevertheless, if groundwater and soil salinisation become
prohibitive for cultivation, it is certain that a rainwater-harvesting system
per greenhouse will no longer be optional.
Comparison of the ecosystem and human well-being impacts of each
technology along with average ranking of each benefit according to
stakeholders.
Rank
Weight
T1
T2
T3
(WB)
Production and socio-economic benefits
Increased irrigation water availability quality
4
0.19
+++
Reduced risk of production failure
5
0.24
++
++
Increased crop yield
3
0.14
+
+
++
Reduced expenses on agricultural inputs
6
0.29
---
+
++
Reduced workload
1
0.05
-
Reduced demand for irrigation water
2
0.10
-
++
Socio-cultural benefits
Conflict mitigation
1
0.33
++
Improved food security/self-sufficiency
2
0.67
+
Ecological benefits
Increased water quantity/quality
9
0.20
+++
Improved harvesting/collection of water
7
0.16
+++
Reduced soil salinity
8
0.18
+++
+
+
Increased biomass above-ground C
4
0.09
++
+
Increased nutrient cycling recharge
6
0.13
++
Increased soil organic matter/below-ground C
5
0.11
++
+
Increased soil moisture
3
0.07
+
Increased biological pest/disease control
1
0.02
+
++
Increased beneficial species (soil biodiversity)
2
0.04
+++
Off-site benefits
Increased water availability
1
1.00
++
(+++): very positive; (++): moderately positive;
(+): slightly positive; (-): slightly negative; (--): moderately
negative; (---): very negative.
The use of green manuring (T2) effectively decreases the required amounts of
fertilisers and pesticides, therefore leading to a healthier soil in a
sustainable way. Based on the practical experience, the cost of the
technology is more or less self-sustained (i.e. the additional costs and
workload are compensated by the reduced agricultural inputs during the
growing season). The requirement of machinery (branch grinder, tiller) that
is not used full-time for greenhouse operations (therefore their purchase
cannot be easily justified for a small land owner) is viewed as a
disadvantage that is hard to overcome if this machinery is not readily
available for lending or renting. Moreover, the technology increases
workload during a period where the greenhouse is otherwise fallow and would
allow a part-time farmer to earn an off-farm income (e.g. from tourism). It
is worth mentioning that only one farmer in the area practices this
technology and had the opportunity to present it to other stakeholders
during the workshop. From their side, stakeholders found the technology and
its conveyed results very promising and worth further investigation to
better identify adoption benefits.
The use of biological agents as crop growth and salinity tolerance amendments
(T3) greatly improves crop production and overall soil functions. Significant
advantages of this technology include the wide variety of biological agents,
and their versatility and adaptability (Harman et al., 2004) that allow
technicians to tailor application to the specific needs of each cultivation
and user. The technology is simple to implement and generates little
additional workload for the end user. Even though the cost of the inoculated
plants or respective soil amendments is significant, the technology is
applied by at least 15 % of the local users, thus underlining the fact
that annual benefits balance out costs. The local farmers' union may provide
the opportunity to scale down high initial costs by placing bulk orders.
Criterial importance and scoring
A second reading of the results based on individual criterial importance
reveals a different narration. Reduced expenses on agricultural inputs and
risk of production failure predominate other production and socio-economic
criteria in the value system of stakeholders (Table 4). This preference
largely counterbalances other benefits of this category yielded by T1,
bringing it on par with those offered by T2 and much lower than those offered
by T3 (Fig. 6). While T1 remains the most all-inclusive solution, it becomes
apparent that for the financially conservative dominated sample (low input,
low risk) investing in this technology does not seem optimal. Since full
costs for adopting T1 have to be borne in advance, the dynamics and
uncertainty about the remaining soil resilience to mismanagement interact to
generate an “option value” associated with postponing T1 (Ghadim and Pannell,
1999). On the other hand, T3 scores higher in the production and
socio-economic criteria domain (Fig. 6).
Cumulative score (Sc) per benefit category for the
three technologies assessed.
![]()
Regarding the three other criteria categories, T1 still yields the highest
impact in terms of significant criteria for sociocultural, ecological, and
off-site benefits (Table 4). It is also notable that stakeholders value food
security and water quality most, while the least valued criteria are pest
species, soil biodiversity, and soil moisture, as greenhouse practices
usually keep these factors under close control. Stakeholder preference for
food security over conflict mitigation suggests a fragmented society with
little coordination and low capacity of adaptation, which is not typical for
rural Greece. Nevertheless, stakeholders are the least interested in reducing
workload, suggesting a high level of diligence and commitment.
Conclusions
The variety and multidisciplinarity of the stakeholders participating in the
workshop allowed for an in-depth discussion on the three most promising
technologies proposed by stakeholders and a comparative analysis driven by
the WOCAT QT process. Using a participatory approach and the impact criteria
from QT (advantages and disadvantages), the impacts of each technology on the
ecosystem and human well-being were identified and evaluated (Table 4).
WOCAT effectively documented SLM technology strengths and weaknesses
according to expert and stakeholder opinion, along with proposed steps for
sustaining and enhancing merits or mitigating inefficiencies. Based on the
results of this application and the feedback of participants, the methodology
facilitates effective multi-stakeholder learning processes (especially in the
case of T2) that contribute to more sustainable management of land.
In the Timpaki case study it is obvious that stakeholders have a preference
towards technologies that promote existing cultivations, rather than more
salt-tolerant crops or alternative land use, signifying the lifelong
commitment to the land and their products. To underline the existence of
expertise, there are indeed examples where the joint effort of technicians
and farmers with adequate investment funds has succeeded with exceptional
results. Discussions revealed that certain farmers are well aware of SLM
practices and are open to sharing their know-how. Nevertheless, the majority
is forced to make short-term plans and focus on short-term profit
maximisation due to financial circumstances and other externalities. To some
extent, the three documented technologies promote sustainable agriculture
management (soil protection and conservation) and reduce production failure
risk and soil salinity. Even though a direct comparison is challenging,
WOCAT has enabled researchers and users to rank technology impacts during
the joint workshop. Results showed that T2 and T3 have a relatively low
recurrent cost and almost direct return but do not present a direct solution
to the soil salinity threat. As a consequence, their applicability and
effectiveness may gradually decline as soil salinity increases. On the other
hand T1 provides a long-term solution that enables the use of additional
technologies and generates returns beyond the annual production. Above soil
sustainability, the wide implementation of rainwater harvesting is bound to
greatly reduce water use conflicts, thus contributing to the general
well-being of the local community.
The negligible spontaneous trend towards adoption of T1 can be largely
attributed to the high establishment cost and the negligible impact of
agricultural input reduction compared to T2 and T3 (i.e. financial returns
may not be immediately apparent). Results support the hypothesis that
stakeholders tend to embrace agronomic and management measures, non-capital
intensive actions, and possibly ephemeral approaches against the soil salinisation
threat. This can be partly explained by a preference to adapt rather than
mitigate and to offset costs of an otherwise uncertain outcome. Findings also
have to be interpreted in the context of the current socio-economic conditions
that have augmented financial uncertainty. Recent research by Micha et
al. (2015) has highlighted the role of the financial crisis along with a
range of social factors in decision making of Greek farmers.
Even though word of mouth conveys the successful results, users are willing
to adopt the technology only if external material support is provided.
Insight attained during the workshop points to a pattern of technology
adoption where a “pioneer” applied a technology first, but the majority of
users will follow only when they have run out of well-established options.
Another explanation is that, for more permanent and costly solutions,
stakeholders tend to anticipate structural and policy solutions to be
implemented by the central government. This often means that the system is
already on the verge of collapse. Possible solutions to meet this challenge
half-way may be for local government to provide incentives (i.e. to
subsidise the technology) or to make it an obligatory requirement for
greenhouse operation.