Salinization tampers with nitrogen uptake too, which slows plant development and causes a yield loss. Another soil salinity effect on agriculture is ionic stress due to harmful ions in soil salts, e.g., chloride or sodium.
How does soil salinity affect agriculture?
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 ).
What is irrigation and soil salinization?
Irrigation is another land management practice that can result in soil salinization. The SAR and EC are also used to classify the quality of water for irrigation (Richards, 1954; see the article “Classification and Mitigation of Soil Salinization” ).
What is saline soil in agriculture?
Saline or sodic soil, besides its natural occurrence, is also a product of intensive agriculture that implements conventional methods and techniques of food production. Their existence and their rapid creation are one of the major threats to food security and sustainability. What are types of soil salinity?
How can we reduce salinization in agriculture?
There are several techniques to tackle salinization and improve agricultural productivity: Increase drainage for better flushing (to remove salts from the ground surface). Plant salt-tolerant crops to manage economic risks and to ensure land cover. Remove salt crystals from the surface mechanically.
What causes soil salination?
What Causes Soil Salinization? Soil salinization occurs when soluble salts are retained in the earth. It happens either naturally or because of improper anthropogenic activities, particularly farming practices. Besides, some earths are initially saline due to low salt dissolution and removal.
How does agriculture cause soil salinization?
Summer fallow management practices may cause increased salinization by increasing the soil moisture content to the point that water moves to seeps on hillslopes. Salts accumulate as the water evaporates from these seeps.
What type of agriculture causes soil salinization?
“Irrigation inevitably leads to the salinization of soils and waters. … In many countries irrigated agriculture has caused environmental disturbances such as waterlogging, salinization, and depletion and pollution of water supplies.
Does fertilizer increase salinity?
Moreover, the release of protons induced the direct release of base cations and accelerated soil salinization. The increase of soil acidity and salinity was attributed to the nitrification of excess N fertilizer.
What is a major cause of soil salinization quizlet?
Soil salinization is the buildup of salt in surface soil layers and is caused by irrigating your crops with salt water, and over-watering crops.
What causes salinization alkalization and waterlogging?
Salinity and the reclamation of salinized lands Salinization is caused by flooding or inundation with saline waters, breaching of dykes, storm surges, tsunamis, or the drying of large inland water bodies. Salinization can result where irrigation waters are compromised by salinity.
Does fertilization cause salinization?
The nitrification of excess N fertilizer led to a large release of protons, and soil acidification may have further induced the direct release of basic cations (Mg 2+ and Ca 2+ ), accelerating soil salinization  .
How can soil salinity be increased?
Human practices can increase the salinity of soils by the addition of salts in irrigation water. Proper irrigation management can prevent salt accumulation by providing adequate drainage water to leach added salts from the soil. Disrupting drainage patterns that provide leaching can also result in salt accumulations.
Which fertilizer cures the salinity of soil?
For decrease the field salinity we can use organic fertilizers such as the green manure and vermicompost. The generally accepted fertilizer is farmyard manure (FYM) for agriculture in most saline areas.
Why does salinity affect yield?
A salinity problem exists if the accumulation of salt in the root zone is at a concentration that causes a reduction in yield. Yield reductions occur when the crop is no longer able to extract sufficient water from the salty soil-water solution. Plant salinity tolerance varies between crops.
When is salinity considered a resource problem?
NRCS considers salinity to be a resource problem when the soil electrical conductivity exceeds the level at which crop yields decline by 10 percent or more. To determine if salinity is a resource problem the NRCS planner needs to know the crops you plant, typical yields, water test results, and soil test results.
How is salinity measured?
Salinity can be measured on a concentration or chemical equivalent basis . Concentration is sometimes expressed at parts per million (PPM) or milligrams per liter (mg/l) and often used for measuring salinity in water. Be aware that 1 PPM equals 1 mg/l which also equals 1 mg/kg. The more preferred measurement expression is on a chemical equivalent basis where the term Electrical Conductivity or EC is used to express salinity. The units typically used for EC are decisiemens per meter (dS/m) or millimohs per centimeter (mmhos/cm). However, it really does not matter which term is used because 1 dS/m is equal to 1 mmhos/cm—one of the more convenient features of the metric system.
What are the characteristics of soil?
Most labs report salinity (ECe) in dS/m. Other soil important soil characteristics include cation exchange capacity (CEC) and pH. Cation Exchange Capacity is an important measure of the soils fertility and potential productivity. Typically, soils with higher silt and clay content have higher CEC values while soils with high sand content have low CEC values. Soils with good CEC values (>10) have a greater ability to attract and hold positive charged particles (cations) which include the salt cations. Soil reaction or pH is an important measure of nutrient availability, solubility of toxic elements, and microbial activity.
What is the definition of salinity?
What is Salinity? Salinity is defined as the total concentration of dissolved mineral solutes in water and or soils. Solutes are comprised of positive charged (cations) elements and negative charged (anions) elements. The more common cations include sodium, calcium, and magnesium.
How to calculate salt loading?
Salt loading is an expression of how much salt is being applied based on concentration (PPM) multiplied by the volume of water applied . Determining the amount of salt applied with irrigation requires using the conversion factor of 1 mg/l = 2.72 lbs/acre foot of water applied. Example: irrigation water has a salt concentration of 1270 PPM (remember PPM=mg/l=mg/kg) you multiply 2.72 X 1270 = 3,454 lbs or 1.7 tons of salt per acre foot of water applied. Sounds like a lot but remember the soil has a tremendous buffering capacity.
How much will the population of the world grow by 2025?
PHOENIX, AZ July 2012 – It is projected that the world’s population will expand to over 8.5 billion by 2025. To keep up with this growth agricultural production must increase by up to 50 percent.
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.
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 ).
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.
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.
How does afforestation affect the groundwater?
Since deep tree roots can efficiently pump underlying shallow groundwater, afforestation of gras slands reverses the vertical flux of groundwater from the soil to the saturated zone.
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 of soil?
Soil salinization refers to the process of salt accumulation in terrestrial landscapes. It occurs naturally where evaporation is high relative to precipitation (there is a seasonal water deficit) and leaching is insufficient to move salts out of the soil profile (Duchaufour, 1982; Schofield & Kirkby, 2003 ), often in landscapes that do not drain into the ocean, called “endorheic” drainage basins. Soils with accumulations of gypsum (CaSO4⋅2H2O) are Gypsisols; those with accumulations of calcium carbonates are Calcisols or sometimes Chernozems and Kastanozems in the World Reference Base (IUSS, 2015 ). Salinity in the form of sodium (Na) salts is associated with “ [s]oils with limitations to root growth,” especially Solonetz (with a high content of exchangeable Na) and Solonchak (with high concentration of soluble salts) Reference Soil Groups (IUSS, 2015; see the article “Classification and Mitigation of Soil Salinization” ); these are the saline soils that have received the most attention from an agricultural perspective because of their extensive area in Europe (e.g., Szabolcs, 1974) and in Australia (e.g., Rengasamy, Chittleborough, & Helyar, 2003; see the article “Soil Salinization” ). However, extensive areas of saline soils occur elsewhere in the world (Ghassemi, Jakeman, & Nix, 1995; Schofield & Kirkby, 2003 ). Soils with a “natric” (from Arabic natroon, salt) diagnostic horizon have a dense subsurface horizon with a distinctly higher clay content than in the overlying horizon (s). A natric horizon has a high content of exchangeable Na and, in some cases, a relatively high content of exchangeable Mg. Diagnostic soil characteristics reflect soil-forming processes, thus the presence of a natric horizon reflects “sodification,” the process of sodium accumulation.
What are the driving forces of soil salinity?
Driving forces for natural soil salinity and alkalinity are climate, rock weathering, ion exchange, and mineral equilibria reactions that ultimately control the chemical composition of soil and water. The major weathering reactions that produce soluble ions are tabled. Where evapotranspiration is greater than precipitation, …
How does sulfuric acid affect water infiltration?
The effectiveness of sulfuric acid as an amendment to improve water infiltration depends upon the actual chemical properties of the soils and water and the application methods (Miyamoto & Stroehlein, 1986 ): when injected into sprinkler lines (a closed water system), the sulfuric acid reacts with HCO3− and CO3= to form carbonic acid and reduces the pH of the water below 7, as long as H2SO4 application rates are less than equivalent concentrations of HCO3−. Upon sprinkling, the carbonic acid decomposes to CO2, thus leading to Ca precipitation and limited effects on sodicity and water infiltration. When applied to open-ditch flow, sulfuric acid removes HCO3− and CO3=, prevents Ca precipitation at pH>7, and may solubilize Ca from soil carbonates. Resulting effects are to maintain or reduce sodicity and to increase electrolyte concentrations, all of which contribute to increasing infiltration of sodic irrigation waters. Water-run application of NH3, a common post-planting fertilization method in row crops, causes precipitation of Ca and induces sodium hazards. Sulfuric acid applied to such water neutralizes alkalinity and minimizes or prevents Ca precipitation and associated infiltration reduction.
How to maintain stable soil structure?
Maintaining a desirable stable soil structure with good permeability depends on controlling the flocculation-dispersion behavior of the soil clay fraction. To use saline-sodic soils for cropping, irrigation water with a high electrolyte concentration and large amounts of Ca2+ and Mg2+ is applied to remove Na+ from the exchange complex without initially changing the electrolyte concentration of the soil solution; then, once the divalent cations are the dominant ones on the exchange complex, the soil can be leached with water of lower electrolyte concentration to remove the excess salts (Richards, 1954 ). Gypsum (CaSO4∙2H2O) or CaCl2 can be applied to remediate sodic soils with low EC by replacing the Na+ on the exchange complex with Ca2+. Na+ is then leached out as a soluble salt, Na2SO4 or NaCl. The addition of gypsum or CaCl2 also increases permeability by increasing the electrolyte concentration.
What is the conductivity of saline soil?
Saline soils are defined those with an electrical conductivity (EC)>4dSm−1 in a saturated paste extract at 25°C, a pH<8.5, and exchangeable Na<15% of total exchangeable cations (Richards, 1954; see the article “Soil Salinization” ). They are distinct from sodic soils with exchangeable Na>15% and, in older literature, alkali soils with a pH>8.5. Salt-affected soils can be saline-sodic, with a saturated paste extract EC>4dSm−1, a pH<8.5, and an exchangeable Na>15% of total exchangeable cations. Soil salinity implies the presence of any salt, including chlorides (Cl−), sulfates (SO42−), nitrates (NO3−), borates (BO33−), carbonates (CO32−), and bicarbonates (HCO3−) of Na, calcium (Ca), magnesium (Mg), potassium (K), and iron (Fe) (Rengasamy, 2006 ). Alkali soil implies the presence of NaHCO3 and Na2CO3, therefore these are also sodic soils. Sodicity refers to the amount of sodium present in a soil. Alkalinization is the process of rise in pH during the accumulation of sodium carbonates (this process is explained in more detail in the section “ Formation of Soil Carbonates and Alkalinity ”).
What is a natric horizon?
A natric horizon has a high content of exchangeable Na and , in some cases, a relatively high content of exchangeable Mg.
How does salt affect soil?
Salt content changes down a soil profile with seasonal moisture fluctuations, evapotranspiration, and infiltration rate, and sometimes soils only experience transient salinization in the subsoil (Rengasamy et al., 2003 ). Secondary salinization can arise when salts accumulate near the soil surface as a result of rising water tables due to land management practices that change the soil hydrology, such as irrigation or tree clearing (Cisneros, Cantero, & Cantero, 1999; Rengasamy, 2006; Schofield, Thomas, & Kirkby, 2001; Williamson, 1986 ). The chemical composition of the irrigation water and underlying water table is critically important in determining the salts that precipitate.
What are types of soil salinity?
Soil salinity in agriculture in a simpler and most correct definition is the high concentrations of salts in the soil profile. The process of salinization can occur either naturally or by anthropogenic activities. The high concentration of salts interrupts the plant’s metabolism making them unable to absorb water, nutrients, and microelements.
Effects of salts on plants
A high concentration of salts in the soil leads to disruption of the osmotic potential in the plant’s cells, especially in the root zone. The osmotic potential is a mechanism with natural flow that allows the transfer of liquid from a medium with high salt content to mediums with lower salt content.
Characteristics of saline soil
Based on the type of soil salinity different soils can be formed, i.e., saline, alkaline, and saline-alkali soils. Saline soil is the soil where there is an excess of sodium salts made from chloride, sulfate, bicarbonates and sodium nitrates and the soil’s aggregates contain exchangeable calcium.
What causes soil salinization
Salinization occurs under certain conditions: field topography prone to salinization process under the influence of capillary movement and evaporation of shallow and saline groundwater, in areas with arid and semi-arid continental-sub-Mediterranean climate with strong evapotranspiration.
How to fix soil salinity
The producers, before making any kind of intervention in order to alleviate this problem of soil salinity in agriculture, need to have specific information regarding the situation on the fields. One of this specific information is the site-specific electrical conductivity map and historical satellite imagery.
How to prevent soil salinization
Soil salinization can be prevented by implementing several strategies in the production management process. The key to success is to have relevant information from the real situation in the field which can be derived from the implementation of various technologies.
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What Causes Soil Salinization?
Soil salinization occurs when soluble salts are retained in the earth. It happens either naturally or because of improper anthropogenic activities, particularly farming practices. Besides, some earths are initially saline due to low salt dissolution and removal. Soil salinization causes include:
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 …
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 does soil salinize?
Soil salinization causes include: dry climates and low precipitations when excessive salts are not flushed from the earth; high evaporation rate, which adds salts to the ground surface; poor drainage or waterlogging when salts are not washed due to a lack of water transportation;
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 happens if the salinity of soil is high?
If the salinity concentration is high enough, the plants will wilt and die, no matter how much you water them. Routine soil testing can identify your soil’s salinity levels and suggest measures you can take to correct the specific salinity problem in your soil.
What are the problems with soil salinity?
Salinity is of greatest concern in soils that are: 1 Irrigated with water high in salts; 2 Poorly drained, allowing for too much evaporation from the soil surface; 3 Naturally high in salts because very little salt leaches out; 4 In areas where the water table (the level or depth to free-flowable water in the soil) is shallow; or In seepage zones, which are areas where water from other locations (normally up slope) seep out.
What are the three types of soils that are most likely to be affected by salt buildup?
Salt buildup can result in three types of soils: saline, saline-sodic and sodic. Saline soils are the easiest to correct; sodic soils are more difficult. Each type of soil has unique properties that require special management.
How does water move through soil?
In areas with shallow water tables, water containing dissolved salts may move upward into the rooting zone. This occurs by capillary action (similar to the way a wick works), where evaporation serves as the suction of water up through the soil (Fig. 2). Water moves the farthest through finer clay and clay loam soils; it moves less in medium-textured soils (loams); and least in coarser, sandy soils.
How to determine the type of problem in soil?
To determine the type of problem in your soil, collect a soil sample and have it tested. The best indicator of the extent of a salt problem is a detailed salinity analysis, in which water is extracted from a paste. This test measures the pH, electrical conductivity (EC) and water-soluble levels of the soil. EC is a measure of the amount of dissolved salts in the paste of soil and water.
Why do some plants survive after others die?
This is why some plants can continue to thrive when others have died. If the salinity concentration in the soil is high enough, the plant will wilt and die , regardless of the amount of water applied.
Why does water not enter the roots?
As the level of salinity in the soil nears that of the roots , however, water becomes less and less likely to enter the root. In fact, when the soil salinity levels are high enough, the water in the roots is pulled back into the soil. The plants become unable to take in enough water to grow.