Austin Stangl & Kaleb Martin
GEOG – 2530
Assignment 4
March 13, 2024
Abstract
Irrigation is seen as a crucial strategy to supply food provisions for our ever-growing population.
However, agricultural systems under heavy irrigation practices, aren’t sustainable considering that these
practices are mechanisms for processes such as soil salinization and waterlogging. Therefore, we
conducted a comprehensive literature review, focusing on providing knowledge on the process of soil
salinization and waterlogging and how irrigation affects these two processes, what irrigation alternatives
and preventative measures we can use to prevent adverse effects of irrigation, and what management
solutions can be incorporated to manage saline lands back to health. We found that the main cause of
salinization and waterlogging is poor irrigation practices that can result in the rise of water tables, and
thus facilitate poor drainage and greater salt concentrations in soils. Additionally, alternative irrigation
practices such as drip irrigation and deficit irrigation can reduce salinization and waterlogging in
agricultural systems, and genetic modifications concerning certain crops can prevent the need for
irrigation practices, and thus limit their associated effects. Lastly, we found that incorporating better
management of drainage systems is one strategy that is important in terms of returning saline lands back
to functionality. Therefore, our findings indicate that current irrigation practices are problematic
considering they’re responsible for most soil salinity in agricultural systems, meaning that how we
manage these systems, in addition to how we manage current saline soils, is important in terms of
mitigating adverse effects related to economic returns, environmental quality, and society in general.
Introduction
Irrigation is becoming necessary in current agricultural systems, with projected trends in the
global population demanding increases in the production of food provisions (Singh, 2021). For instance,
adopting irrigation practices has resulted in a 400% increase in food production and economic returns for
arid and semi-arid regions (Fernandez-Cirelli et al., 2009). However, continual use of certain irrigation
practices has also resulted in increased instances of environmental degradation. For instance, Flood
irrigation is commonly responsible for soil salinization — a process particularly problematic considering
its contributions to salt concentrations in soils and source water (Singh, 2015). In arid and semi-arid
regions, salt concentrations are generally higher, considering their climatic conditions are associated with
increased rates of evapotranspiration (Singh, 2015). Moreover, this process of evapotranspiration, due to
increased flood irrigation, causes changes in the hydrological cycle, since it causes the water table to rise
through the transportation of saline groundwater toward the soil surface, allowing for greater salt
concentrations within topsoils, and increased instances of waterlogging (Michael, 2009). As a result, this
process has important economic implications, with estimated economic losses of 27 billion in terms of
crop yields(Shahid et al., 2018). Additionally, soil salinization was responsible for societal failure in
ancient Mesopotamia during 1700-2100 BC, where salinity resulted in many cultivations being
abandoned (Jacobsen & Adams, 1958). Lastly, regarding human health, increased soil salinity promotes
the transportation of contaminants into source water, causing many adverse health effects (Nachshon,
2018; Chakraborty et al., 2019). Therefore, in this literature review, we will provide a comprehensive
explanation for why salinization and waterlogging are such a threat in these irrigated systems, in addition
to discussing alternatives and preventative measures to mitigate irrigation, and overall management
strategies to return saline land to health.
The Threat of salinization and waterlogging
The salinization process is important since it can dictate how land and irrigation systems should
be managed to mitigate waterlogging and ensure soil drainage to maintain crop productivity and the flow of the hydrological cycle. As mentioned, salinization in agriculture is mostly due to poor irrigation
practices, with over 20% of irrigated land being negatively affected by salinization and waterlogging,
with projections estimating an increase of 30% by 2050 (Singh, 2020). In particular, salinization can
inhibit food production worldwide and frequently occurs because of poor drainage on agricultural fields
— actively speeding up salinization and waterlogging (Zhang et al., 2020; Wang et al., 2020; Jiang et al.,
2019; Singh, 2020). Therefore, the long-term sustainability of irrigated farming is threatened by soil
salinization, where three percent of soils globally are salt-affected (FAO, 2020). Moreover, salt-affected
fields are particularly troublesome in semi-arid regions, considering they’re responsible for yield
decreases of 18-43 percent (Wichelns & Qadir, 2015; Chang et al., 2019). In terms of waterlogging, this
process enhances salinization and can occur in both natural and artificial conditions. In the case of
natural conditions, waterlogging can occur from deep rain percolation, submergence caused by floods,
and poor natural aggregation of the subsoil. For artificial conditions, waterlogging can occur because of
unlined canals used in irrigation projects, which causes water to enter underground reservoirs as seepage
(Singh, 2020). As mentioned, Semi-arid regions under heavy irrigation are most at risk of salinization
and waterlogging, with salinization occurring in 33% of Egypt’s irrigated land, 23% in the United States,
30% in Iran, 34% in Argentina, and 18% in South Africa (Ghassemi et al., 1995). Therefore, this issue of
waterlogging must be prevented to mitigate these adverse effects. More specifically, the water table
depth threshold must not be surpassed, since if these thresholds are ignored, it can inhibit plant growth
and cause declines in crop yields (Evans & Fausey, 1999; Wesseling, 1974). Furthermore, irrigation is
responsible for threats of shallow water table-induced salinization, which occurs often in irrigated
farmlands, since evapotranspiration due to certain irrigation processes is intensified by reduced water
tables (Chandio et al., 2013; Chen et al., 2020; Gebremeskel et al., 2018; Liang et al., 2018; Youssef et
al., 2018).
Alternative Irrigation Practices/Preventative Measures
As previously mentioned, certain irrigation practices implemented in arid and semi-arid regions
are responsible for increased soil salinity, with 50% of irrigated land in these regions becoming saline
(Sakadevan & Nguyen, 2010). Therefore, it’s apparent that current irrigation practices need to be reduced
or improved to mitigate the impact of soil salinization on aspects related to economic returns, the
environment, and human health. One approach that could accomplish this is by adopting more
sustainable irrigation techniques. For instance, micro-irrigation techniques such as drip irrigation, could
be beneficial in managing salinity levels in topsoils (Cuevas et al., 2019). Moreover, this practice
prevents water evaporation by applying water directly to the crop roots, which promotes salt-leaching
between crops and soils, reducing the concentration of salt in topsoils (Cuvas et al., 2019). Additionally,
practices such as deficit irrigation — which allocates water to crops at levels below optimal growth
requirements — allow for greater water conservation within soils, therefore preventing instances of
irrigation, and thus decreasing evaporation and soil salinity (Cuevas et al., 2019). Additional
preventative measures could also include genetically modifying crops to become more drought-resistant.
For instance, compounds such as glycine betaine can be supplemented in certain crops to conserve water,
since this compound helps to maintain homeostasis with water levels in their internal and external
environments (Gosal et al., 2009). Furthermore, improved irrigation techniques and alternative practices
that reduce the need for flood irrigation, actively reduce instances of soil salinity and thus limit these
adverse effects.
Management Solutions for Saline Soils
In terms of managing soils that are already saline, it is essential to manage rising water tables,
drainage frameworks, and the conjunctive use of diverse water sources to control soil salinization while
incorporating new technologies and models (Singh, 2020). It is important to use known knowledge of the
different salt tolerances for different crops, planting crops that are more suited for the saline severity, and
engineering plants that have higher salt tolerances (Singh, 2020). Globally, there is motivation to manage
salinization as it is crucial to meet certain Sustainable Development Goals: goal one being ‘Zero Hunger
’ and goal Fifteen ‘Life on the Land’(Singh, 2020). Currently, there are poor feedback-supported
simulation models used for managing soil salinization, where these models can be improved by
integrating enhanced sensing methods and larger-scale waterlogging parameters (Singh, 2020).
Therefore, building new structural frameworks of drainage systems containing the rising water table,
conjunctive water use, and the utilization of models and geospatial strategies, is essential to rectifying
these issues (Singh, 2020). Firstly, drainage systems reduce the water volume in agricultural systems,
which is essential for lowering the water table and allowing salts to discharge (Jouni et al., 2018). For
instance, these drainage methods could include windmills, used in the Netherlands as tools for turning
deep lakes into low-laying areas bounded by a dike, where the water level could be controlled
independently (Bos & Boers, 1994). In terms of main drainage systems, these can include drainage tiles,
moles, and tubewells, which can be used to improve soil characteristics (Singh, 2020). Additionally, new
technological management systems incorporating GIS or remote sensing can be used to evaluate
salinization and drainage issues in irrigated zones (Singh, 2020). However, these Newer models need to
include farmer feedback to help facilitate the control of groundwater pumping (Singh, 2020).
Furthermore, awareness is continually needed through the solution-finding process to reduce water
usage, promote drainage in soils, and manage soil salinity, to allow for these saline lands to return to
health.
Conclusion
The urgency to address soil salinization and waterlogging on irrigated lands should not be
underestimated for the damage it can cause to society globally. There must be incentives and motivators
put into place for using alternative irrigation methods along with updated drainage frameworks. The
push for drip irrigation or better water management techniques alongside improving crop genetics can be solutions to mitigate this global issue. New effective management strategies of saline soils must be found as there is a continual reduction of improper irrigation of farmland. The integration of sustainable
practices and innovative solutions will improve crop productivity in all affected fields. Beyond on-thefarm implementation and updation, there must be more collaborative efforts across research and policy
to ensure agriculture globally can be more resilient and adaptable to these pressing challenges as well as
climate change.
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