how does agriculture lead to salinization of soil

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What Causes Soil Salinization

  1. Irrigation Water Quality & Volume The total amount of dissolved salt in irrigated water and its composition affects soil salt content. …
  2. Fertilizer Composition Some fertilizers contain high contents of potentially harmful salts, such as potassium chloride or ammonium sulphate. …
  3. High Evaporation & Transpiration

The most influential human-induced factors are land use, farming systems, land management and land degradation. Inappropriate irrigation practices (such as the use of salt-rich irrigation water) and insufficient drainage both cause salinisation.

Full
Answer

What is soil salinity and what causes?

Salinization of farmland is a fast-growing problem worldwide. Due to rising sea levels, vast areas of formerly arable land become increasingly saline. Since most farmers around the globe are unfamiliar with saline agriculture, their common belief is that saline soil is …

How does salinity affect plant growth and yield?

 · Salinization of soil negatively impacts plant development and induces land degradation. Saline earths show lower agricultural productivity, worsen farmers’ wellbeing, and the economic situation in the region. Managing soil salinity at early stages helps to reverse it. However, heavy contamination leads to complete loss of farmlands and desertification due to …

How does over irrigation lead to salinization?

The excess salts cause many types of crops to wither and die. The salts prevent plant roots from making use of water in the soil. Plant roots absorb water from the soil through the process of osmosis. Osmosis moves water from an area of lower salt (higher water) concentration to an area of higher salt concentration.

How do you fix salty soil?

High annual evaporation (and/or transpiration), low annual precipitation and restricted soil drainage, combine to create salt affected soils in depressions or lowlands. As the water evaporates, salts dissolved from the soil deposit and accumulate at the soil surface. Notice the crust of salt deposited on the ground and on the base of the fence post.

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What is a major cause of soil salinization?

Human activities can cause salinization through the use of salt-rich irrigation water, which can be exacerbated by overexploitation of coastal groundwater aquifers causing seawater intrusion, or due to other inappropriate irrigation practices, and/or poor drainage conditions.

How does agriculture lead to salinization of soil apes?

salinization can be caused by excessive irrigation. water deposits salts which prevent infiltration and leaves water closer to the surface. In dry areas this water evaporates quickly leaving the salt behind.

How does agriculture cause salinization and how is it detrimental to crops?

Unfortunately, due to a process called soil salinization we are facing a major threat to sustaining arable land. Salinization occurs when water-soluble salts accumulate in the soil, leading to a series of environmental problems such as land degradation, reduced crop yields, and contaminated freshwater.

How does salinization affect agriculture?

Salinity becomes a problem when enough salts accumulate in the root zone to negatively affect plant growth. Excess salts in the root zone hinder plant roots from withdrawing water from surrounding soil. This lowers the amount of water available to the plant, regardless of the amount of water actually in the root zone.

Which type of irrigation causes salinization?

Drip irrigation is a technique that can be used in areas where the ground water level is high and in danger of suffering from a high salt content. Where salinization is a problem to plants, enough water can be added to the irrigation process to leach salts away from plant roots.

What is salinity in agriculture?

Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean.

How does salinization occur?

Salinization occurs when dissolved salts in water tables rise to the soil surface and accumulate as water evaporates. Often rise in a water table is due to the replacement of deep-rooted vegetation, such as trees, with shallower rooted vegetation, such as grasses.

What is a major environmental problem caused by using the agricultural practice of tilling?

A major environmental problem caused by the agricultural practice of tilling is soil erosion.

Which of these is an impact of agriculture on the environment?

Agriculture contributes to a number larger of environmental issues that cause environmental degradation including: climate change, deforestation, biodiversity loss, dead zones, genetic engineering, irrigation problems, pollutants, soil degradation, and waste.

What are the short term and long term impacts of increasing soil salinity to agricultural land?

Salinity affects production in crops, pastures and trees by interfering with nitrogen uptake, reducing growth and stopping plant reproduction. Some ions (particularly chloride) are toxic to plants and as the concentration of these ions increases, the plant is poisoned and dies.

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How does salinization affect agriculture?

Salinization of soil negatively impacts plant development and induces land degradation. Saline earths show lower agricultural productivity, worsen farmers’ wellbeing, and the economic situation in the region. Managing soil salinity at early stages helps to reverse it. However, heavy contamination leads to complete loss of farmlands …

How to deal with soil salinization?

The best way to deal with soil salinization is not to let it happen. In case it did, it is important to eradicate the problem – the sooner, the better, before the consequences get too severe. So, soil salinization solutions deal with prevention and management.

What is salinization of soil?

Salinization of soil is an excessive accumulation of water-soluble salts. Typically, it is table salt NaCl. The list is far more extensive and includes various compounds of sodium, potassium, calcium, magnesium, sulfates, chlorides, carbohydrates, and bicarbonates. In general, salt-affected earths are categorized as saline, sodic and saline-sodic, depending on the content.

Why is the soil saline?

Besides, some earths are initially saline due to low salt dissolution and removal. Soil salinization causes include:

How does salinity affect plants?

The major soil salinity effect on plant growth is tampering with water absorption. Even with sufficient soil moisture, crops wade and die due to the inability to take up enough water.

How many acres of land have been lost due to salinization?

The United Nations University states that about 5,000 acres have been lost daily all over the world because of salinization since the 1990s, as of 2014.

Why is crop monitoring important?

Crop Monitoring may assist the process of reducing soil salinity. Shallow-rooted plants may not reach subsoil moisture, and extra subsoil moisture may induce salinity. Crop Monitoring provides reports on surface soil moisture and root-zone moisture, facilitating the choice of crops for planting in the exact areas.

What is the process of soil salinization?

Soil salinization is a major process of land degradation that decreases soil fertility and is a significant component of desertification processes in the world’s dryland (Thomas and Middleton, 1993 ).

What is salinization of soil?

Soil salinization is often associated with sodic soil. Natural or anthropogenic accumulation of sodium in the system leads to gradual replacement of divalent cations with Na + on the exchange complex of clay minerals.

How does salinization affect rice?

Soil salinization is a widespread problem and a major abiotic constraint affecting the global food production and threatening food security. Plant growth, development and yield are severally reduced under saline conditions. Rice (Oryza sativa L.) is the staple food in many countries which feeds millions of people across the world. However, rice plant, being glycophyte in nature, is sensitive to salinity which results in several adverse morphological, physiological, biochemical, and molecular changes leading to reduction in biomass production and grain yield. Effects of salinity on rice occur at two stages that is, at the initial phase of plant development the osmotic effects rapidly reduce plant growth and the second slow phase of plant response to salinity when symptoms of salinity-induced toxicity appear. At morphological levels, shoot and root growth, above- and below-ground biomass production, number of tillers and spikelets and grain yield of rice are adversely affected. Disruption in photosynthetic activity and pigment production, membrane permeability and integrity, Na + /K + balance across the membrane and production of reactive oxygen species causing oxidative damage are the major responses of rice at physiological level. In addition to agronomic practices to reduce soil salinity, salt tolerance cultivar of rice have been developed containing traits such as ion exclusion and tolerance of both the osmotic and tissue effects of salinity. The modern biotechnological marker-based genetic engineering approaches have helped the researchers to use a combination of genes to develop salt-tolerant and high yielding rice varieties. The other approaches to reduce salinity stress in plants include the use of salt-tolerant microbial inoculants/biofertilizers, silicon and manganese fertilization and phytohormones.

How much salinization affects the Mediterranean?

Soil salinization affected about 1–3 million hectares especially in the Mediterranean countries where irrigation farming is very common and many fields have reached soil salinity levels which prevents farmers from raising common crops.

What is the most serious environmental problem in Australia?

In Australia, soil salinization is the most severe environmental problem of the continent, causing a dramatic change in landscape, industry, and the future of farmland ( Dehaan and Taylor, 2002 ). The accumulation of soluble salts in soil occurs when evaporation exceeds precipitation and salts are not leached but remain in …

How much of Egypt’s land is salinized?

In Egypt, almost 35% of the agricultural land suffers from salinity ( Kotb et al., 2000; Kim and Sultan, 2002 ). Soil salinization is the first stage of environmental destruction caused by salinity and is interrelated with river and lake salinization.

Why are poaceae important?

Poaceae is the most economically important plant family because 70% of all crops are salt-sensitive grasses. About 3.6 billion ha from 5.2 billion ha of the world’s agricultural land is already salt-affected and not suitable for conventional crop farming. In contrast, the demand for food is continuously increasing and we expect to need to feed around nine billion by the end of 2050 ( Millar and Roots, 2012 ). However, extensive efforts are underway to improve the salinity tolerance of conventional crops either through breeding or modern molecular techniques, but still no crop can tolerate half the level of salinity of seawater. In such a scenario, a major breakthrough in crop breeding for salinity tolerance is needed. Regulation of the number, size, and shape of the salt-excreting structure—trichome could be one such possibility. About 15% of halophytic grasses excrete Na + and Cl − through bicellular microhairs, which are present on the leaf surface ( Adams et al., 1998 ). Aeluropus lagopoides (Linn.) Trin. Ex Thw. is a salt-excreting, salinity- (1000 mmol L −1 NaCl; Gulzar et al., 2003) and drought-tolerant ( Mohsenzadeh et al., 2006) grass. Therefore, it could be used as a model plant to improve the salinity tolerance of crops like rice, wheat, and maize ( Flowers and Colmer, 2008 ). Detailed ecological and physiological studies on A. lagopoides have been carried out ( Waghmode and Joshi, 1982; Sher et al., 1994; Abarsaji, 2000; Gulzar et al., 2003 ). However, information related to the function of its Na + transport genes in salinity is lacking. Therefore, the goals of this study were: (i) to isolate the cDNA sequences of VNHX and PMNHX from A. lagopoides; (ii) to observe the change in the expression of both genes under saline condition; and (iii) to explore the role of both genes in the salt tolerance of A. lagopoides.

What are the problems with salinity in agriculture?

Salinity in Agriculture. Salinity problems reduce productivity on both irrigated and non-irrigated agricultural lands in the United States and throughout the world. Salt-affected soils on Colorado range land. High annual evaporation (and/or transpiration), low annual precipitation and restricted soil drainage, combine to create salt affected soils …

What causes salt in soil?

High annual evaporation (and/or transpiration), low annual precipitation and restricted soil drainage, combine to create salt affected soils in depressions or lowlands. As the water evaporates, salts dissolved from the soil deposit and accumulate at the soil surface.

What are the training notes for soil?

Training Note 1: Determining So il Salinity in the Field From Measurements of Electrical Conductivity. Training Note 2: Effects of Salts on Soils and Plants. Training Note 3: Assessing the suitability of Saline Water for Irrigation. Training Note 4: Practices to Control Salinity in Irrigated Soils.

How does salt affect plants?

Soil salt levels can greatly influence plant survival and growth. The effect of high-salt soils in the Northern Plains and Rocky Mountains, for example, is dramatic. It is estimated that 300,000 acres in Montana alone have been removed from production because of increased salinity.

What are the subjects of salts?

Subjects include effects of salts on soil and plants; methods of sampling, monitoring, and measuring salinity; use of saline drainage water in irrigation; methods of managing salinity;

How many pages are in the soil quality test kit?

The Soil Quality Test Kit Guide (prepared by NRCS and ARS) is an 82-page booklet containing procedures for 12 on-farm tests, an interpretive section for each test, data recording sheets, and a section on how to build the kit. Chapter 5 includes an electrical conductivity test for salinity. See Section II for salt tolerance of selected crops.

What is soil salinization?

Soil salinization refers to the salinity of the level affecting agricultural and environmental health. Soil salinization usually occurs in arid areas. In these areas, soluble salt ions accumulate in the soil. In these areas where plant growth requires irrigation, the Evaporation and transpiration process leaves salt in the soil.

How to control salinity in soil?

1. Control irrigation water volume. Apply minimal levels of irrigation water volume and keep the well-drained soil condition. 2. Grow Salt Tolerant Crops. It’s one of the best ways to deal with a soil salinity problem, especially if you are starting. Plant salt-tolerant cash crops such as barley, sunflowers, or canola.

How does salt affect water quality?

1. Irrigation Water Quality & Volume. The total amount of dissolved salt in irrigated water and its composition affects soil salt content. The more water you spray, the salinity of the soil will be close to the salt concentration of the irrigation water. When the soil is dry, the concentration of salt in the soil will increase.

Why do plants need salt?

In these areas where plant growth requires irrigation, the Evaporation and transpiration process leaves salt in the soil. In the beginning, salts will reduce soil productivity and limit crop yields. When the salinity increases, it will kill the vegetation and soil microorganism. Then the perfectly fertile soil will become completely barren.

What happens to the soil when it is dry?

When the soil is dry, the concentration of salt in the soil will increase. Besides, the poor soil drainage leads to low permeability; the salt will accumulate on the soil surface. 2. Fertilizer Composition.

Why does water reduce plant growth?

It’s the principal cause of reduced plant growth and yield as salinity mounts. Water moves into plant roots by this process, which is controlled by the level of salts in the soil water.

What are the harmful chemicals in fertilizer?

Some fertilizers contain high contents of potentially harmful salts, such as potassium chloride or ammonium sulphate. Overuse and abuse of fertilizer lead to increasing salinity in the soil.

How does salinity affect agriculture?

Agricultural crops exhibit a spectrum of responses under salt stress. Salinity not only decreases the agricultural production of most crops, but also, effects soil physicochemical properties, and ecological balance of the area. The impacts of salinity include—low agricultural productivity, low economic returns and soil erosions, (Hu and Schmidhalter, 2002). Salinity effects are the results of complex interactions among morphological, physiological, and biochemical processes including seed germination, plant growth, and water and nutrient uptake (Akbarimoghaddam et al., 2011; Singh and Chatrath, 2001). Salinity affects almost all aspects of plant development including: germination, vegetative growth and reproductive development. Soil salinity imposes ion toxicity, osmotic stress, nutrient (N, Ca, K, P, Fe, Zn) deficiency and oxidative stress on plants, and thus limits water uptake from soil. Soil salinity significantly reduces plant phosphorus (P) uptake because phosphate ions precipitate with Ca ions (Bano and Fatima, 2009). Some elements, such as sodium, chlorine, and boron, have specific toxic effects on plants. Excessive accumulation of sodium in cell walls can rapidly lead to osmotic stress and cell death (Munns, 2002). Plants sensitive to these elements may be affected at relatively low salt concentrations if the soil contains enough of the toxic element. Because many salts are also plant nutrients, high salt levels in the soil can upset the nutrient balance in the plant or interfere with the uptake of some nutrients (Blaylock et al., 1994). Salinity also affects photosynthesis mainly through a reduction in leaf area, chlorophyll content and stomatal conductance, and to a lesser extent through a decrease in photosystem II efficiency (Netondo et al., 2004). Salinity adversely affects reproductive development by inhabiting microsporogenesis and stamen filament elongation, enhancing programed cell death in some tissue types, ovule abortion and senescence of fertilized embryos. The saline growth medium causes many adverse effects on plant growth, due to a low osmotic potential of soil solution (osmotic stress), specific ion effects (salt stress), nutritional imbalances, or a combination of these factors (Ashraf, 2004). All these factors cause adverse effects on plant growth and development at physiological and biochemical levels (Munns and James, 2003), and at the molecular level (Tester and Davenport, 2003).

How does salinity affect crop production?

Salinity is one of the most brutal environmental factors limiting the productivity of crop plants because most of the crop plants are sensitive to salinity caused by high concentrations of salts in the soil, and the area of land affected by it is increasing day by day. For all important crops, average yields are only a fraction – somewhere between 20% and 50% of record yields; these losses are mostly due to drought and high soil salinity, environmental conditions which will worsen in many regions because of global climate change. A wide range of adaptations and mitigation strategies are required to cope with such impacts. Efficient resource management and crop/livestock improvement for evolving better breeds can help to overcome salinity stress. However, such strategies being long drawn and cost intensive, there is a need to develop simple and low cost biological methods for salinity stress management, which can be used on short term basis. Microorganisms could play a significant role in this respect, if we exploit their unique properties such as tolerance to saline conditions, genetic diversity, synthesis of compatible solutes, production of plant growth promoting hormones, bio-control potential, and their interaction with crop plants.

How does salinity affect plant growth?

In order to assess the tolerance of plants to salinity stress, growth or survival of the plant is measured because it integrates the up- or down-regulation of many physiological mechanisms occurring within the plant. Osmotic balance is essential for plants growing in saline medium. Failure of this balance results in loss of turgidity, cell dehydration and ultimately, death of cells. On the other hand, adverse effects of salinity on plant growth may also result from impairment of the supply of photosynthetic assimilates or hormones to the growing tissues (Ashraf, 2004). Ion toxicity is the result of replacement of K+by Na+in biochemical reactions, and Na+and Cl−induced conformational changes in proteins. For several enzymes, K+acts as cofactor and cannot be substituted by Na+. High K+concentration is also required for binding tRNA to ribosomes and thus protein synthesis (Zhu, 2002). Ion toxicity and osmotic stress cause metabolic imbalance, which in turn leads to oxidative stress (Chinnusamy et al., 2006). The adverse effects of salinity on plant development are more profound during the reproductive phase. Wheat plants stressed at 100–175 mM NaCl showed a significant reduction in spikelets per spike, delayed spike emergence and reduced fertility, which results in poor grain yields. However, Na+and Cl−concentrations in the shoot apex of these wheat plants were below 50 and 30 mM, respectively, which is too low to limit metabolic reactions (Munns and Rawson, 1999). Hence, the adverse effects of salinity may be attributed to the salt-stress effect on the cell cycle and differentiation. Salinity arrests the cell cycle transiently by reducing the expression and activity of cyclins and cyclin-dependent kinases that results in fewer cells in the meristem, thus limiting growth. The activity of cyclin-dependent kinase is diminished also by post-translational inhibition during salt stress. Recent reports also show that salinity adversely affects plant growth and development, hindering seed germination, seedling growth, enzyme activity (Seckin et al., 2009), DNA, RNA, protein synthesis and mitosis (Tabur and Demir, 2010; Javid et al., 2011).

What are the effects of salt on soil?

Rhizosphere microorganisms, particularly beneficial bacteria and fungi, can improve plant performance under stress environments and, consequently, enhance yield both directly and indirectly (Dimkpa et al., 2009). Some plant growth-promoting rhizobacteria (PGPR) may exert a direct stimulation on plant growth and development by providing plants with fixed nitrogen, phytohormones, iron that has been sequestered by bacterial siderophores, and soluble phosphate (Hayat et al., 2010). Others do this indirectly by protecting the plant against soil-borne diseases, most of which are caused by pathogenic fungi (Lutgtenberg and Kamilova, 2009). The problem of soil salinization is a scourge for agricultural productivity worldwide. Crops grown on saline soils suffer on an account of high osmotic stress, nutritional disorders and toxicities, poor soil physical conditions and reduced crop productivity. The present review focuses on the enhancement of productivity under stressed conditions and increased resistance of plants against salinity stress by application of plant growth promoting microorganisms.

How can salinization be reduced?

Salinization can be restricted by leaching of salt from root zone , changed farm management practices and use of salt tolerant plants. Irrigated agriculture can be sustained by better irrigation practices such as adoption of partial root zone drying methodology, and drip or micro-jet irrigation to optimize use of water. The spread of dry land salinity can be contained by reducing the amount of water passing beyond the roots. This can be done by re-introducing deep rooted perennial plants that continue to grow and use water during the seasons that do not support annual crop plants. This may restore the balance between rainfall and water use, thus preventing rising water tables and the movement of salt to the soil surface (Manchanda and Garg, 2008). Farming systems can change to incorporate perennials in rotation with annual crops (phase farming), in mixed plantings (alley farming, intercropping), or in site-specific plantings (precision farming) (Munns et al., 2002). Although the use of these approaches to sustainable management can ameliorate yield reduction under salinity stress, implementation is often limited because of cost and availability of good water quality or water resource. Evolving efficient, low cost, easily adaptable methods for the abiotic stress management is a major challenge. Worldwide, extensive research is being carried out, to develop strategies to cope with abiotic stresses, through development of salt and drought tolerant varieties, shifting the crop calendars, resource management practices etc. (Venkateswarlu and Shanker, 2009) as shown in Fig. 1.

What are the environmental problems that affect agriculture?

Various environmental stresses viz. high winds, extreme temperatures, soil salinity, drought and flood have affected the production and cultivation of agricultural crops, among these soil salinity is one of the most devastating environmental stresses, which causes major reductions in cultivated land area, crop productivity and quality (Yamaguchi and Blumwald, 2005; Shahbaz and Ashraf, 2013). A saline soil is generally defined as one in which the electrical conductivity (EC) of the saturation extract (ECe) in the root zone exceeds 4 dS m−1(approximately 40 mM NaCl) at 25 °C and has an exchangeable sodium of 15%. The yield of most crop plants is reduced at this ECe, though many crops exhibit yield reduction at lower ECes (Munns, 2005; Jamil et al., 2011). It has been estimated that worldwide 20% of total cultivated and 33% of irrigated agricultural lands are afflicted by high salinity. Furthermore, the salinized areas are increasing at a rate of 10% annually for various reasons, including low precipitation, high surface evaporation, weathering of native rocks, irrigation with saline water, and poor cultural practices. It has been estimated that more than 50% of the arable land would be salinized by the year 2050 (Jamil et al., 2011).

Why are salt tolerant crops important?

Development of salt-tolerant crops has been a major objective of plant breeding programs for decades in order to maintain crop productivity in semiarid and saline lands. Although several salt-tolerant varieties have been released, the overall progress of traditional breeding has been slow and has not been successful as only few major determinant genetic traits of salt tolerance have been identified (Schubert et al., 2009; Dodd and Perez-Alfocea, 2012). 25 years ago Epstein et al. (1980)described the technical and biological constraints to solving the problem of salinity. Although there has been some success with technical solutions to the problem, the biological solutions have been more difficult to develop because a pre-requisite for the development of salt tolerant crops is the identification of key genetic determinants of stress tolerance. The existence of salt-tolerant plants (halophytes) and differences in salt tolerance between genotypes within salt-sensitive plant species (glycophytes) indicates that there is a genetic basis to salt response (Yamaguchi and Blumwald, 2005). Although a lot of approaches have been done for development of salt tolerant plants by transgenics complete success is not achieved yet. The assessment of salt tolerance in transgenic experiments has been mostly carried out using a limited number of seedlings or mature plants in laboratory experiments. In most of the cases, the experiments were carried out in greenhouse conditions where the plants were not exposed to those conditions that prevail in high-salinity soils (e.g. alkaline soil pH, high diurnal temperatures, low humidity, and presence of other sodic salts and elevated concentrations of selenium and/or boron). The salt tolerance of the plants in the field needs to be evaluated and, more importantly, salt tolerance needs to be evaluated as a function of yield. The evaluation of field performance under salt stress is difficult because of the variability of salt levels in field conditions (Richards, 1983) and the potential for interactions with other environmental factors, including soil fertility, temperature, light intensity and water loss due to transpiration. Evaluating tolerance is also made more complex because of variation in sensitivity to salt during the life cycle. For example, in rice, grain yield is much more affected by salinity than in vegetative growth (Khatun and Flowers, 1995). In tomato, the ability of the plants to germinate under conditions of high salinity is not always correlated with the ability of the plant to grow under salt stress because both are controlled by different mechanisms (Foolad and Lin, 1997), although some genotypes might display similar tolerance at germination and during vegetative growth (Foolad and Chen, 1999). Therefore, the assessment of stress tolerance in the laboratory often has little correlation to tolerance in the field. Although there have been many successes in developing stress-tolerant transgenics in model plants such as tobacco, Arabidopsisor rice (Grover et al., 2003), there is an urgent need to test these successes in other crops. There are several technical and financial challenges associated with transforming many of the crop plants, particularly the monocots. First, transformation of any monocot other than rice is still not routine and to develop a series of independent homozygous lines is costly, both in terms of money and time. Second, the stress tolerance screens will need to include a field component because many of the stress tolerance assays used by basic researchers involve using nutrient-rich media (which in some cases include sucrose). This type of screen is unlikely to have a relationship to field performance. Third, because saline soils are often complex and can include NaCl, CaCl2, CaSO4, Na2SO4, high boron concentrations and alkaline pH, plants that show particular promise will eventually have to be tested in all these environments (Joseph and Jini, 2010).

What is salinization in agriculture?

Soil salinization is a kind of soil degradation that adversely influences the production of food worldwide and needs immediate attention for alleviation. Climate change further aggravates soil degradation, by accentuating the process of soil salinization. Plants respond differently to the instances of soil salinity, depending on their variety, stages of growth, etc. Therefore certain salt-tolerant species could be identified and used for alleviation of saline soils.

How does salinization affect the environment?

Salinization is a global environmental phenomenon that affects many different aspects of our life (Williams, 2001a, b): changing the chemical composition of natural water resources (lakes, rivers, and groundwater), degrading the quality of water supply to the domestic and agriculture sectors, contribution to loss of biodiversity, tax onomic replacement by halotolerant species (Williams, 2001a, b), loss of fertile soil , collapse of agricultural and fishery industries , changing of local climatic conditions , and creating severe health problems (e.g., the Aral Basin).

Why is salinization important?

Salinization of water resources has two main reasons: it is closely connected to irrigation and, in coastal areas, it is related to saltwater intrusions due to overpumping of groundwater in coastal aquifers (Figure 25 ).

How to reduce salinity in arid soil?

As irrigation qualifies as the single most important cause of soil salinization in the arid and semiarid regions of the world, the alleviation and management practices consist mostly of the different combinations of water management. Flushing, leaching, etc. could help alleviate the problem of soil salinization at the level of an agricultural field. However, the management of saline soil requires good drainage systems in place. Genetic breeding of salt-tolerant varieties of plants could be beneficial in alleviating salinity, but the use of microorganisms could be affordable too. Most saline areas have saline sources of water for irrigation as well. Such areas could manage crop production by resorting to frequent irrigation with larger amounts of water.

What causes salinization in aquifers?

Salinization is an increase in the total dissolved solids (TDS) of the aquifer caused by natural or anthropogenic factors. The processes and sources of salinization vary for inland and coastal aquifers. In urban areas located inland, salinization may be due to geogenic or anthropogenic factors (Fig. 13.3 ). Saline water naturally underlies freshwater aquifers at greater depths in some regions ( Martens and Wichmann, 2007 ). When the water from these saline aquifers is discharged onto the surface, the fresh water aquifers may also be contaminated. It is also possible that the salt water and fresh water mixes in the subsurface and the salinity of fresh water aquifer is increased. The salinity of aquifers depends on the distribution and rates of precipitation, evapotranspiration and recharge rates, type of aquifer material and its characteristics, residence time, flow velocities, and nature of the discharge areas ( Richter and Kreitler, 1993 ). Aquifers in contact with salt deposits also turn saline due to natural rock-water interaction processes. Water pumped from these saline aquifers cannot be directly used for water supply or industrial purposes. Australia, being a dry continent, is highly affected by salinization, therefore groundwater in many parts of the country is naturally saline. Major anthropogenic sources of inland salinization in urban areas include irrigation of dry areas that lack proper drainage, increased evaporation and decreased precipitation facilitated by climate change, excessive groundwater pumping, wastewater with a high salt content being disposed of carelessly by industries onto the surface, etc ( Foster and Chilton, 2003, Zimmermann-Timm, 2007 ). Irrigation and heavy groundwater pumping-induced salinization is commonly reported in India and Pakistan.

How does irrigation affect water quality?

Increased recharge related to cultivation with irrigation in semiarid regions can degrade water quality by flushing nutrients, in addition to salts, into underlying aquifers ( Scanlon et al., 2007 ). For example, the salinity of the Yellow River has been increasing significantly in the last four decades as a result of saline irrigation return flows ( Chen et al., 2003 ). Also in the Murray–Darling Basin in Australia, stream salinity is a major concern since several decades ( Jolly et al., 2001 ).

What is the biggest problem in arid and semiarid regions?

Salinization , which is the biggest troublemaker in arid and semiarid regions, and subsequent alkalization will result in the deterioration of the physical, chemical, fertility, and biological properties of soil and loss of organic matter in soil due to excess salt and sodium accumulation in fertile agricultural areas.

What is soil salinization?

What’s Soil Salinization. Soil salinization is one of the most vital soil problems for agricultural production. Salinization refers to the salt content of the level affecting agricultural and environmental health. Soil salinization usually occurs in arid areas, In these areas, soluble salt ions accumulate in the soil.

How does salt affect soil?

In the beginning, the salt will reduce soil productivity and limit crop yield s. As the salt content increases, it kills the vegetation and soil microorganism. As a result, The perfectly fertile soil will become completely barren.

Why do plants wilt when the soil is saturated?

High salt concentration results in high osmotic potential of the soil solution, so the plant has to use more energy to absorb water. Under extreme salinity conditions , plants may be unable to absorb water and will wilt, even when the surrounding soil is saturated. 2. Specific Ion Toxicity.

How does salinity affect plants?

Salinity affects almost all processes of plants’ growth. 1. Osmotic Stress. This is the principal cause of reduced plant growth and yield as salinity mounts. Water moves into plant roots by this process, which is controlled by the level of salts in the soil water.

Why does salt accumulate on the soil surface?

In addition, the poor soil drainage leads to low permeability, the salt will accumulate on the soil surface.

Where does salinization occur?

Soil salinization usually occurs in arid areas, In these areas, soluble salt ions accumulate in the soil. In these areas where plant growth requires irrigation, the Evaporation and transpiration process leaves salt in the soil.

What crops can be planted to reduce soil salinity?

Plant salt-tolerant cash crops such as barley, sunflowers, or canola. Not only are they equipped to deal with the salt, but also drought tolerant.

How to prevent soil salinization?

Management to prevent soil salinization involves maintaining a mix of deep-rooted perennial vegetation and crops in order to prevent the rise of the water table, and limiting the amount of irrigation water that is applied to the system. However, the management of dryland salinity is complicated by the difficulty of understand groundwater dynamics and the long delays (decades to centuries) between action and response in some dryland groundwater systems. Long-term methods to keep the groundwater level below the root-zone include planting of deep-rooted vegetation and salt tolerant plants. However, while planting the halt the rise of a water table it will likely take decades to lower it. Apart from the direct effects of lowering the water table and reducing the salt concentration in the topsoil, if the planting of deep-rooted vegetation can be linked to economically beneficial activities this strategy can contribute to increasing the diversity of the agricultural system. This may improve soil health and make the ecosystem less vulnerable to disturbances (Anderies 2005).

What is salinization in soil?

Summary. Soil salinization is a serious and difficult to reverse form of soil degradation. Salinization occurs when dissolved salts in water tables rise to the soil surface and accumulate as water evaporates. Often rise in a water table is due to the replacement of deep-rooted vegetation, such as trees, with shallower rooted vegetation, …

How does salinization affect ecosystems?

Where crops are grown, the salinization regime shift negatively impacts ecosystem services such as food production, livestock feed, protection from soil erosion, human nutrition, livelihoods and economic activity. Freshwater becomes contaminated with salt, which can reduce the availability of drinking water, reduce fish and other aquatic populations, and damage infrastructure. In saline soil biodiversity is reduced as only salt-tolerant species can live in saline soil. Availability of wild plant and animal products are also reduced. Farmers lose the security of their livelihoods due to lost crop yield and degraded soil and water.

What are the effects of saline topsoil?

The saline topsoil regime is characterized by elevated water tables, significantly higher than normal soil salt levels and reduced plant growth across the landscape. High concentrations of salt in the topsoil reduce the uptake of water by plants and impede nutrient absorption. Some salts may also be toxic to plants when present in high concentrations, inhibiting plant growth. Under extreme salinization, a white crust of salt accumulates at the soil surface, and only salt tolerant plants are able to grow. Persistent high water tables change the hydrology of local aquifers considerably. Surface water becomes brackish, harmful to wildlife and unsuitable for irrigation. In cultivated regions, crop yields are restricted, threatening livelihoods and reducing food and nutrition. High levels of salt in freshwater can make water non-drinkable and harm wildlife and corrode water infrastructure, roads, and bridges (Neilsen et al. 2003; Pannell 2002).

Why do deep rooted plants evaporate water?

Deep rooted plants evaporate water from the soil, prevents water tables from rising and salinization of the root soil profile. The lack of salt in the soil profile in turn enables the persistence of deep-rooted vegetation. Crop plants that are grown are adapted to arid climates and are able to efficiently use available water.

How does salinity affect agriculture?

Salts continue to be deposited to the soil surface as long as the water table remains in the root zone. Salinity impedes the ability of plants to use water, which reduces growth rate . At higher levels of salinity plants are damaged, older leaves die and photosynthetic leaf area is reduced, until plants die (Munns 2002). If salts are not flushed below the root zone, land can becomes unproductive for the long term. A social feedback that can maintain the saline regime is an agricultural dependence on irrigation. Producing crops for large-scale markets often requires for continued intensive production to be viable. Investments in irrigation equipment can become a sunk cost, as their expense necessitates their continued use. As salt accumulate in the soil profile, producers become further dependent on irrigation to flush salts below the root zone. This agricultural system maintains the knowledge, infrastructure, and resources to conduct irrigated agriculture, but does not support other approaches to agriculture (Allison and Hobbs 2004).

How do arid landscapes survive drought?

Arid landscapes with normal topsoil salt levels have diverse communities of perennial plants that have evolved deep roots to survive periods of drought. These plants continually use and transpire water as it becomes available , so that little water infiltrates to the ground water. Where cultivation occurs, drought tolerant crops are grown and irrigation is not part of agricultural practice. The presence of deep-rooted native vegetation maintains the normal regime, as they have evolved to efficiently use the limited precipitation in arid and semi-arid areas. Deep rooted plants evaporate water from the soil, prevents water tables from rising and salinization of the root soil profile. The lack of salt in the soil profile in turn enables the persistence of deep-rooted vegetation. Crop plants that are grown are adapted to arid climates and are able to efficiently use available water. A social feedback that maintains this regime is the reproduction of agricultural and land management practices that maintain deep rooted plants and do not use irrigation (Pannell 2002; Anderies et al. 2006).

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