This explains the remaining alkalinity (or rather basicity) in the form of soluble sodium hydroxide and the high pH or low pOH.

The presence of abundant Na+ ions in the soil solution and the precipitation of Ca2+ ions as a solid mineral causes the clay 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 (EDL), see the corresponding figure)[6] and, in exchange, release previously adsorbed Ca2+, by which their exchangeable sodium percentage (ESP) is increased as illustrated in the same figure.

The quality of the irrigation water in relation to the alkalinity hazard is expressed by the following two indexes: which must not be much higher than 1 and preferably less than 0.5.

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.

[10] 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.

Poly-houses filter the intense summer solar radiation in tropical countries to save the plants from water stress and leaf burns.

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.

Continuous drip irrigation 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 or cheaper alum or aluminium sulfate.

Alternatively, gypsum (calcium sulfate, CaSO4 · 2 H2O) can also be applied as a source of Ca2+ ions to replace the sodium at the exchange complex.

Where urea is made available cheaply to farmers, it is also used to reduce the soil alkalinity / salinity primarily.

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.

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.

Saline soils are mostly also sodic (the predominant salt is sodium chloride), but they do not have a very high pH nor a poor infiltration rate.

[14] Since the 1990s, research and experimentation have been conducted in China and elsewhere for remediation and utilization of alkali land via combined agriculture and aquaculture practices, with considerable success and gains in experience.

[15][20][21][16] FAO noted in a recent newsletter that alkaline land is one area that there are innovative ways and opportunities for aquaculture to expand.