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Alkali, or Alkaline, soils are
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
soils with high pH (greater than 8.5), a poor
soil structure Soil structure describes the arrangement or the way of soil in the solid parts of the soil and of the pore space located between them. It is determined by how individual soil granules clump, bind together, and aggregate, resulting in the arrangem ...
and a low infiltration capacity. Often they have a hard
calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...
layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swellManaging irrigation water quality, Oregon State University, USA
Retrieved on 2012-10-04.
and difficult to clarify/settle. They derive their name from the
alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
group of elements, to which sodium belongs, and which can induce
basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. R ...
. Sometimes these soils are also referred to as ''alkaline
sodic soils 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 ...
''.
Alkaline soils are
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College i ...
, but not all basic soils are
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of ...
ne.


Causes

The causes of soil alkalinity can be natural or man-made: # The natural cause is the presence of soil minerals producing sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) upon weathering. # Coal-fired boilers / power plants, when using coal or lignite rich in limestone, produce
ash Ash or ashes are the solid remnants of fires. Specifically, ''ash'' refers to all non-aqueous, non-gaseous residues that remain after something burns. In analytical chemistry, to analyse the mineral and metal content of chemical samples, ash ...
containing
calcium oxide Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "''lime''" connotes calcium-containing inorganic ...
. CaO readily dissolves in water to form slaked lime, Ca(OH)2, and carried by rain water to rivers / irrigation water.
Lime softening Lime softening (also known as lime buttering, lime-soda treatment, or Clark's process) is a type of water treatment used for water softening, which uses the addition of limewater (calcium hydroxide) to remove hardness (deposits of calcium and magnes ...
process precipitates Ca2+ and Mg2+ ions / removes hardness in the water and also converts sodium bicarbonates in river water into sodium carbonate. Sodium carbonates (washing soda) further reacts with the remaining Ca2+ and Mg2+ in the water to remove / precipitate the total hardness. Also water-soluble sodium salts present in the ash enhance the sodium content in water. The global
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead ...
consumption in the world was 7.7 billion tons in the year 2011. Thus river water is made devoid of Ca2+ and Mg2+ ions and enhanced Na+ by coal-fired boilers. # Many sodium salts are used in industrial and domestic applications such as sodium carbonate, sodium bicarbonate (baking soda), sodium sulphate, sodium hydroxide (caustic soda),
sodium hypochlorite Sodium hypochlorite (commonly known in a dilute solution as bleach) is an inorganic chemical compound with the formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may also be viewed as the sodium salt of h ...
(bleaching powder), etc. in huge quantities. These salts are mainly produced from sodium chloride (common salt). All the sodium in these salts enter into the river / ground water during their production process or consumption enhancing water sodicity. The total global consumption of sodium chloride is 270 million tons in the year 2010. This is nearly equal to the salt load in the mighty
Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of ...
. Man made sodium salts contribution is nearly 7% of total salt load of all the rivers. Sodium salt load problem aggravates in the downstream of intensively cultivated river basins located in China, India, Egypt, Pakistan, west Asia, Australia, western US, etc. due to accumulation of salts in the remaining water after meeting various transpiration and evaporation losses. # Another source of man made sodium salts addition to the agriculture fields / land mass is in the vicinity of the wet cooling towers using sea water to dissipate
waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ( ...
generated in various industries located near the sea coast. Huge capacity cooling towers are installed in oil refineries, petrochemical complexes, fertilizer plants, chemical plants, nuclear & thermal power stations, centralized HVAC systems, etc. The drift / fine droplets emitted from the cooling towers contain nearly 6% sodium chloride which would deposit on the vicinity areas. This problem aggravates where the national pollution control norms are not imposed or not implemented to minimize the drift emissions to the best industrial norm for the sea water based wet cooling towers. # The man-made cause is the application of softened water in irrigation (surface or ground water) containing relatively high proportion of sodium bicarbonates and less calcium and magnesium.


Agricultural problems

Alkaline soils are difficult to take into agricultural production. Due to the low
infiltration capacity Infiltration is the process by which water on the ground surface enters the soil. It is commonly used in both hydrology and soil sciences. The infiltration capacity is defined as the maximum rate of infiltration. It is most often measured in meter ...
, rain water stagnates on the soil easily and, in dry periods, cultivation is hardly possible without copious irrigated water and good drainage. Agriculture is limited to crops tolerant to surface waterlogging (e.g. rice, grass) and the productivity is lower.


Chemistry

Soil alkalinity is associated with the presence of sodium carbonate (Na2CO3) or sodium bicarbonate (NaHCO3) in the soil,US Salinity Lab Handbook 60
/ref> either as a result of natural weathering of the soil particles or brought in by irrigation and/or flood water. This salt is extremely soluble, when it undergoes
hydration Hydration may refer to: * Hydrate, a substance that contains water * Hydration enthalpy, energy released through hydrating a substance * Hydration reaction, a chemical addition reaction where a hydroxyl group and proton are added to a compound * ...
, it dissociates in: : → 2 + The carbonate anion , is a weak base accepting a proton, so it hydrolyses in water to give the
bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemic ...
ion and a
hydroxyl ion Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...
: : + → + which in turn gives carbonic acid and hydroxyl: : + → + See
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
for the equilibrium of carbonate-bicarbonate-carbon dioxide. The above reactions are similar to the dissolution of calcium carbonate, the solubility of the two salts being the only difference. Na2CO3 is about times more soluble than CaCO3, so it can dissolve far larger amounts of , thus rising the pH to values higher than 8.5, which is above the maximum attainable pH when the equilibrium between calcium carbonate and dissolved carbon dioxide are in equilibrium in soil solution. :''Notes'': :* Water (H2O) is partly dissociated into H3O+ (
hydronium In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is d ...
) and OH ( hydroxyl) ions. The
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conv ...
H3O+ has a positive electric charge (+) and its concentration is usually written as + The hydroxyl ion OH has a negative charge (−) and its concentration is written as H :* In pure water, at 25 °C, the
dissociation constant In chemistry, biochemistry, and pharmacology, a dissociation constant (K_D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex f ...
of water (''K''w) is 10−14.
Since Kw = +× H then both the concentration of H3O+ and OH ions equal 10−7 M (a very small concentration). :* In neutral water, the pH, being the negative decimal logarithm of the H3O+ concentration, it is 7. Similarly, the pOH is also 7. Each unit decrease in pH indicates a tenfold increase of the H3O+ concentration. Similarly, each unit increase in pH indicates a tenfold increase of the OH concentration. :* In water with dissolved
salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...
, the concentrations of the H3O+ and the OH ions may change, but their sum remains constant, namely . A pH of 7 therefore corresponds to a pOH of 7, and a pH of 9 with a pOH of 5. :* Formally it is preferred to express the ion concentrations in terms of
chemical activity In chemical thermodynamics, activity (symbol ) is a measure of the "effective concentration" of a species in a mixture, in the sense that the species' chemical potential depends on the activity of a real solution in the same way that it would depen ...
, but this hardly affects the value of the pH. :* Water with excess H3O+ ions is called acid (), and water with excess OH ions is called alkaline or rather basic (). Soil moisture with is called very acid and with very alkaline (basic). H2CO3 ( carbonic acid) is unstable and produces H2O (water) and CO2 ( carbon dioxide gas, escaping into the atmosphere). This explains the remaining
alkali In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of ...
nity (or rather
basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. R ...
) in the form of soluble sodium hydroxide and the high pH or low pOH. Not all the dissolved sodium carbonate undergoes the above chemical reaction. The remaining sodium carbonate, and hence the presence of ions, causes CaCO3 (which is only slightly soluble) to precipitate as solid calcium carbonate (limestone), because the product of the concentration and the Ca2+ concentration exceeds the allowable limit. Hence, the calcium ions Ca2+ are immobilized. The presence of abundant Na+ ions in the soil solution and the precipitation of Ca2+ ions as a solid mineral causes the
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
particles, which have negative electric charges along their surfaces, to adsorb more Na+ in the ''diffuse adsorption zone'' (DAZ, also more commonly called '' diffuse double layer'' (DDL), or
electrical double layer A double layer (DL, also called an electrical double layer, EDL) is a structure that appears on the surface of an object when it is exposed to a fluid. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. The D ...
(EDL), see the corresponding figure)G.H. Bolt (ed.), 1981. Soil chemistry: A. basic elements. Vol 5a, Elsevier, Amsterdam, The Netherlands and, in exchange, release previously adsorbed Ca2+, by which their ''exchangeable sodium percentage'' (ESP) is increased as illustrated in the same figure. Na+ is more mobile and has a smaller electric charge than Ca2+ so that the thickness of the DDL increases as more sodium ions occupy it. The DDL thickness is also influenced by the total concentration of ions in the soil moisture in the sense that higher concentrations cause the DDL zone to shrink. Clay particles with considerable ESP (> 16), in contact with non-saline soil moisture have an expanded DDL zone and the soil swells (
dispersion Dispersion may refer to: Economics and finance *Dispersion (finance), a measure for the statistical distribution of portfolio returns *Price dispersion, a variation in prices across sellers of the same item *Wage dispersion, the amount of variatio ...
). The phenomenon results in deterioration of the
soil structure Soil structure describes the arrangement or the way of soil in the solid parts of the soil and of the pore space located between them. It is determined by how individual soil granules clump, bind together, and aggregate, resulting in the arrangem ...
, and especially crust formation and compaction of the top layer. Hence the infiltration capacity of the soil and the water availability in the soil is reduced, whereas the surface-water-logging or surface runoff is increased. Seedling emergence and crop production are badly affected. :''Note'': :* Under saline conditions, the many ions in the soil solution counteract the swelling of the soil, so that saline soils usually do not have unfavorable physical properties. ''Alkaline soils, in principle, are not saline since the alkalinity problem is worse as the salinity is less.'' Alkalinity problems are more pronounced in
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...
soils than in loamy, silty or sandy soils. The clay soils containing montmorillonite or smectite (swelling clays) are more subject to alkalinity problems than illite or kaolinite clay soils. The reason is that the former types of clay have larger
specific surface Specific surface area (SSA) is a property of solids defined as the total surface area of a material per unit of mass, (with units of m2/kg or m2/g) or solid or bulk volume (units of m2/m3 or m−1). It is a physical value that can be used to dete ...
areas (''i.e.'' the surface area of the soil particles divided by their volume) and higher
cation exchange capacity Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with ot ...
(CEC). :''Note'': :* Certain clay minerals with almost 100% ESP (i.e. almost fully sodium saturated) are called
bentonite Bentonite () is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite. Na-montmorillonite has a considerably greater swelling capacity than Ca-mon ...
, which is used in civil engineering to place impermeable curtains in the soil, e.g. below dams, to prevent seepage of water. The quality of the irrigation water in relation to the
alkalinity Alkalinity (from ar, القلوي, al-qaly, lit=ashes of the saltwort) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength o ...
hazard is expressed by the following two indexes:
  1. The
    sodium adsorption ratio The Sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils. It is an indicator of the suitability of water for use in agricultural irrigation, as determined from the concentrations of t ...
    (SAR, ) The formula for calculating sodium adsorption ratio is: :SAR = = where: stands for concentration in
    milliequivalents An equivalent (symbol: officially equiv; unofficially but often Eq) is the amount of a substance that reacts with (or is ''equivalent'' to) an arbitrary amount (typically one mole) of another substance in a given chemical reaction. It is an arch ...
    /liter (briefly meq/L), and stands for concentration in mg/L. It is seen that Mg ( magnesium) is thought to play a similar role as Ca (
    calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...
    ). The SAR should not be much higher than 20 and preferably less than 10; When the soil has been exposed to water with a certain SAR value for some time, the ESP value tends to become about equal to the SAR value.
  2. The residual sodium carbonate (RSC, meq/L): The formula for calculating the residual sodium carbonate is: which must not be much higher than 1 and preferably less than 0.5. The above expression recognizes the presence of
    bicarbonates In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemica ...
    (), the form in which most carbonates are dissolved.
While calculating SAR and RSC, the water quality present at the root zone of the crop should be considered which would take into account the leaching factor in the field. The partial pressure of dissolved CO2 at the plants root zone also decides the calcium present in dissolved form in the field water. USDA follows the adjusted SAR for calculating water sodicity.


Soil improvement

Alkaline soils with solid CaCO3 can be reclaimed with grass cultures, organic compost, waste hair / feathers, organic garbage, waste paper, rejected lemons/oranges, etc. ensuring the incorporation of much acidifying material (inorganic or
organic material Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
) into the soil, and enhancing dissolved Ca in the field water by releasing CO2 gas.Chhabra, R. 1996. Soil Salinity and Water Quality. 284 pp. Oxford & IBH Publishing Co. Pvt. Ltd., New Delhi (South Asian edition) and A.A. Balkema Uitgevers BC, Rotterdam (edition elsewhere). . Deep
ploughing A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are drawn by tractors. A plough may have a wooden, iron or ...
and incorporating the calcareous subsoil into the top soil also helps. Many times salts' migration to the top soil takes place from the underground water sources rather than surface sources. Where the underground water table is high and the land is subjected to high solar radiation, ground water oozes to the land surface due to capillary action and gets evaporated leaving the dissolved salts in the top layer of the soil. Where the underground water contains high salts, it leads to acute salinity problem. This problem can be reduced by applying
mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A ...
to the land. Using poly-houses or shade netting during summer for cultivating vegetables/crops is also advised to mitigate soil salinity and conserve water / soil moisture. Poly-houses filter the intense summer solar radiation in tropical countries to save the plants from water stress and leaf burns. Where the ground water quality is not alkaline / saline and ground water table is high, salts build up in the soil can be averted by using the land throughout the year for growing plantation trees / permanent crops with the help of lift irrigation. When the ground water is used at required leaching factor, the salts in the soil would not build up. Plowing the field soon after cutting the crop is also advised to prevent salt migration to the top soil and conserve the soil moisture during the intense summer months. This is done to break the capillary pores in the soil to prevent water reaching the surface of the soil. Clay soils in high annual rain fall (more than 100 cm) areas do not generally suffer from high alkalinity as the rain water runoff is able to reduce/leach the soil salts to comfortable levels if proper rainwater harvesting methods are followed. In some agricultural areas, the use of subsurface "tile lines" are used to facilitate drainage and leach salts. Continuous
drip irrigation Drip irrigation or trickle irrigation is a type of micro-irrigation system that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surface. ...
would lead to alkali soils formation in the absence of leaching / drainage water from the field. It is also possible to reclaim alkaline soils by adding acidifying minerals like
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...
or cheaper
alum An alum () is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula , where is a monovalent cation such as potassium or ammonium. By itself, "alum" often refers to potassium alum, with the ...
or
aluminium sulfate Aluminium sulfate is a salt with the formula Al2 (SO4)3. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking water and wastewater treatment plant ...
. Alternatively,
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
(
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, ...
, · 2 ) can also be applied as a source of Ca2+ ions to replace the sodium at the exchange complex. Gypsum also reacts with sodium carbonate to convert into sodium sulphate which is a neutral salt and does not contribute to high pH. There must be enough natural drainage to the underground, or else an artificial subsurface drainage system must be present, to permit leaching of the excess sodium by percolation of rain and/or irrigation water through the
soil profile A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...
.
Calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Ca ...
is also used to reclaim alkali soils. CaCl2 converts Na2CO3 into NaCl precipitating CaCO3. NaCl is drained off by leaching water.
Calcium nitrate Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an inorganic compound with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhy ...
has a similar effect, with NaNO3 in the leachate. Spent acid (HCl, H2SO4, etc.) can also be used to reduce the excess Na2CO3 in the soil/water. Where
urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important ...
is made available cheaply to farmers, it is also used to reduce the soil alkalinity / salinity primarily. The ammonium () cation produced by urea hydrolysis which is a strongly sorbing
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
exchanges with the weakly sorbing Na+ cation from the soil structure and Na+ is released into water. Thus alkali soils adsorb / consume more urea compared to other soils. To reclaim the soils completely one needs prohibitively high doses of amendments. Most efforts are therefore directed to improving the top layer only (say the first 10 cm of the soils), as the top layer is most sensitive to deterioration of the
soil structure Soil structure describes the arrangement or the way of soil in the solid parts of the soil and of the pore space located between them. It is determined by how individual soil granules clump, bind together, and aggregate, resulting in the arrangem ...
. The treatments, however, need to be repeated in a few (say 5) years' time. Trees / plants follow gravitropism. It is difficult to survive in alkali soils for the trees with deeper rooting system which can be more than 60 meters deep in good non-alkali soils. It will be important to refrain from irrigation (ground water or surface water) with poor quality water. In viticulture, adding naturally occurring chelating agents such as tartaric acid to irrigation water has been suggested, to solubilize calcium and magnesium carbonates in sodic soils.Ashworth, J. 2007. The effect of chelating agents on soil sodicity. Soil and Sediment Contamination 16: 301-312. One way of reducing sodium carbonate is to cultivate
glasswort The glassworts are various succulent, annual halophytic plants, that is, plants that thrive in saline environments, such as seacoasts and salt marshes. The original English glasswort plants belong to the genus '' Salicornia'', but today the gla ...
or
saltwort Saltwort is a common name for various genera of flowering plants that thrive in salty environments, typically in coastal salt marshes and seashores, including: :*''Salsola'' and related genera within subfamily ''Salsoloideae'' :*''Salicornia'' :*'' ...
or
barilla ''Barilla'' refers to several species of salt-tolerant ( halophyte) plants that, until the 19th century, were the primary source of soda ash and hence of sodium carbonate. The word "barilla" was also used directly to refer to the soda ash obtaine ...
plants. These plants sequester the sodium carbonate they absorb from alkali soil into their tissues. The ash of these plants contains good quantity of sodium carbonate which can be commercially extracted and used in place of sodium carbonate derived from common salt which is highly energy intensive process. Thus alkali lands deterioration can be checked by cultivating barilla plants which can serve as food source, biomass fuel and raw material for soda ash and potash, etc.


Leaching saline sodic soils

Saline soils 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 ...
are mostly also sodic (the predominant salt is sodium chloride), but they do not have a very high pH nor a poor infiltration rate. Upon leaching they are usually not converted into a (sodic) alkali soil as the Na+ ions are easily removed. Therefore, saline (sodic) soils mostly do not need gypsum applications for their reclamation.Chacupe case study
/ref>


See also

* Ammonia volatilization from urea * Agreti green vegetable *
Barilla ''Barilla'' refers to several species of salt-tolerant ( halophyte) plants that, until the 19th century, were the primary source of soda ash and hence of sodium carbonate. The word "barilla" was also used directly to refer to the soda ash obtaine ...
*
Biosalinity Biosalinity is the study and practice of using saline (salty) water for irrigating agricultural crops. Many arid and semi-arid areas actually do have sources of water, but the available water is usually brackish (0.5–5g/L salt) or saline (30� ...
*
Cation-exchange capacity Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with ot ...
*
Drip irrigation Drip irrigation or trickle irrigation is a type of micro-irrigation system that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surface. ...
*
Environmental impact of irrigation The environmental effects of irrigation relate to the changes in quantity and quality of soil and water as a result of irrigation and the subsequent effects on natural and social conditions in river basins and downstream of an irrigation scheme. ...
* Fertilizer * Halotolerance * Index of soil-related articles * Phosphate rich organic manure * Phosphogypsum *
Red mud Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a second ...
*
Residual Sodium Carbonate Index The residual sodium carbonate (RSC) index of irrigation water or soil water is used to indicate the alkalinity hazard for soil. The RSC index is used to find the suitability of the water for irrigation in clay soils which have a high cation exchan ...
* Sajji Khar * Soda lake * Soil fertility *
Soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the ne ...
*
Soil salinity 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 ...
*
Soil salinity control Soil salinity control relates to controlling the problem of soil salinity and reclaiming salinized agricultural land. The aim of soil salinity control is to prevent soil degradation by salination and reclamation of already salty (saline) soils ...


References

{{DEFAULTSORT:Alkali Soils Alkaline soils Land reclamation