Accumulation of access salt in the top layers of soil which tends to effect the soil productivity partially or fully is referred to as soil salinization and is a worldwide phenomenon (Abrol et al., 1988). Soils are most known to be effected to salinity mostly in arid and semiarid climates but could be found in waterlogged areas, where a lot saline water has accumulated (Sparks, 2003). Humid regions salt soils are less affected because rainfall then manages to leach excess salts out of the soil, that eventually mixes with the groundwater and finally into the oceans. Salt affected soils are known to exist along sea coast regions near river where saline water has affected the soil with salt content (Richards, 1954).
Causes of soil salinization are variable like drainage, poor drainage can cause salinity due to low soil permeability caused by high salinity of water. Soil permeability is 'The ease with which gases, liquids or plant roots penetrate or pass through a bulk mass of soil or a layer of soil '(Soil science society of America, 2008). Poor drainage eventually could result into salt lakes. Secondary from of soil salinized caused by human activities are by Oversupply of water or irrigating non saline soils with ground water of high salinity could introduce salt into the soils (Mainguet, 1999).Irrigation in access in places where climate is dry could result into salinity as evaporation of saline water leaves salt behind on the top soil layer. Tsunami tidal waves also contribute towards soil salinization as they deposit salty seawater on large flooded areas resulting in accumulation of salt in soils which could last for several years to a short time, heavy rainfall could manage to flush salt out of the soil. Aridification or drought, which tends to increase evaporation of surface or underground waters will lead to a concentration of salts and their precipitation thus contributing towards soil salinization. Other Rock weathering and rainfall contribute to soil salinization to some extent .Rainwater contains low amount of salt but over time can accumulate over the landscapes soil.
It has been found that worldwide 76.6Mha of land is salinized due to human activities over the last 40-50 years. It has been estimated that the world is losing at least three hectares of arable land every minute to soil salinization, making it second only to soil erosion as the leading worldwide cause of soil degradation (Lal,2002). Salinization is mostly spread due to irrigated agriculture most evident in countries throughout Asia and Africa, with large impact on India and china and large proportions effected in Australia, Argentina, Egypt, Iran, Pakistan and USA .It is most serious in Egypt and Pakistan where most of the agricultural production is irrigation based .The UK is not affected by soil salinization due to a healthy balance and evapotranspiration. But as climate change starts affecting the climate and causing floods, it would then give rise to ground water table which would leach historic salt layers. Some of the coastal parts are effected by soil salinization by salt in salt marshes along the coast.
Salt effects plants by changing the pH of the soil as well as changes the mineral content eventually the roots will dry due to excess salt as it leaches water from the soil. Soil salinity restrains water uptake by plants and reduces their ability to survive and produce affecting the horticultural sector and agriculture (Rengasamy, 2002).High salt levels in soils will eventually effect water quality reducing the amount of fresh water for use. Crops produced would become highly toxic making them inedible and resulting in loses in the horticultural and agricultural sector and in worst case scenario shortage of food ,accumulation of salts in the root zone eventually have drastic effects on the growth and yield of horticultural crops. Soil salinization may end up in desertification of lands if not took measures to prevent it.
Total salt levels in the soil are measured by how well soils conduct electricity, the more salt it contains the better it conducts .The strategies available for the managing of soil salinization depend upon its specific local cause .The primary management methods are leaching and drainage in other words lowering of the water table (Maliva and Missimer, 2012).Some deep percolation is necessary in order to prevent salt build up in the plant root zone. The leaching requirements depend upon the salt tolerance of crops and the salinity of water used for irrigation, leaching involves the process of flushing the salts out of the soil, one needs to apply a lot of water -6 inches of water will leach half of the salt out of the top foot of soil (Stell, 1998).leaching can't work unless the soil is well drained thus improving drainage of soil first is mandatory. Where ground water levels are high underground drainage systems need to be installed but on the downside is highly costly and wastes water, to reduce water loses drainage water could be recycled and used for irrigation. Efficient irrigation could reduce the problem as salt content in water used for irrigation from rivers and groundwater contain salts that dry behind after irrigation, inefficient irrigation causes waterlogging by which salt is accumulated. Switching to salt tolerant crops will help prevent salinization to a degree. To clean-up the soil another measure would be to stop growing crops on the land for about 2-5 years.
Abrol, I. P., Yadav, J. S. P., & Massoud, F. I. (1988) Salt-affected soils and their management. Rome: Food and Agriculture Organization of the United Nations.
Lal, R. (2002) Encyclopaedia of soil science. New York: Marcel Dekke
Mainguet, M. (1999) Aridity: Droughts and human development; with 25 tables. Berlin [u.a.: Springer.
Maliva, R., & Missimer, T. (2012) Arid lands water evaluation and management. Berlin: Springer.
Rengasamy, P. (2002) 'Transient salinity and subsoil constraints to dry land farming in Australian sodic soils: an overview'. Australian Journal of Experimental Agriculture, 42,351'361.
Richards, L.A. (1954) Diagnosis and improvement of saline and alkali soils. USDA Agricultural Handbook 60.
Soil Science Society of America. (2008) Glossary of soil science terms 2008. Madison, Wis: Soil Science Society of America.
Sparks, D. L. (2003) Environmental soil chemistry. London: Academic Press.
Stell, E. (1998). Secrets to great soil: A grower's guide to composting, mulching, and creating healthy, fertile soil for your garden and lawn. Pownal, Vt: Storey Pub.