Soil salinity

Salinization is an excessive accumulation of water-soluble salts in the soil. It examines the processes by which accumulate in the upper soil layer salts, the characteristics and the causes. Salinization is next to the acidification of two possible long-term results of soil development. To salinization occurs when the soil has a negative water balance, ie the evaporation is greater in six to nine months a year, when the rainfall. In addition to the natural development of soil salinization by human activity can be greatly accelerated.

Strictly speaking, must be between salinization, the accumulation of slightly soluble salts and alkalization, the accumulation of sodium bicarbonate and sodium carbonate at the same time increasing pH, distinguished. A special case of salinization is the sodification, in which primarily sodium chloride (table salt) is enriched in the surface.

Furthermore, the origin of the salts involved is important. You can come out of the atmosphere ( atmogene salts). In these cases, one also speaks of " Tagwasserversalzung ". The salts can be transported by rising ground water in the upper soil layers. This is called " Grundwasserversalzung ", which can occur for example in coastal regions of the huminden zones, for example by excessive extraction of groundwater, can penetrate into the body of groundwater by seawater. Efflorescent minerals can leave salts to the environment, and fossil salts ( marine sediment ) may occur as the source. In addition to these natural sources and artificial irrigation and fertilizer may come into question.

• 4.1 Solonchak
• 4.2 solonietz
• 4.3 Calcisol
• 4.4 Gypsisol

Physical process

The physical process is often very similar. The high evaporation at the surface leads to dissolved salts accumulate in the water at the surface. Since no water flows, the salts remain in the upper soil layer. For irrigation, the effect is magnified because now there is more water to transport the salts available. Additional salt load by the use of ground water further enhances the effect.

Importance of salinity

Salinisation is the second largest soil protection problem that affects 20% of the agricultural land and 50 % of all irrigated areas.

In Syria alone 30 to 35 percent of cultivated land have been lost by salinity. In Egypt, there are 30 to 40 percent in Pakistan less than 40 percent in Iraq and 50 percent in the United States 20 to 25 percent. In part, this goes back to the irrigation system of the Sumerians in Mesopotamia. Only through drip irrigation and drainage systems can be counteracted. As a countermeasure only medium in the history of many regions also significant detectable change of cultivated plant species recorded, for example, from wheat to salt more resistant barley.

Also in rice cultivation it comes to salinization. In the dry season the rice fields be watered so that the salinity of standing water in which the rice grows, increased by the strong evaporation.

In the shore areas of decline in waters such as the Aral Sea or the Dead Sea may lead to massive salt encrustation. There are plants ( halophytes ), which are adapted to saline soils, however, can not be used for agriculture.

Antidote

The most common method of land salinized to take into use again, is the large-scale irrigation and draining the water through drainage, before the sun has dried the solution. This " flushing" must usually be performed more than once.

The salinity can also be counteracted by the incorporation of special substrate mixtures. The operating principle of this technique is, superabsorbent introduce such a way that it neither comes to gel formation, which denied the water the roots will simply washed away by rain water, but to make the water in the absorbers the roots largely and directly accessible. Thus, the irrigation amount and frequency are greatly reduced and so the salting risk mitigation. The substrates can also be combined with fertilizing properties.

Effect of salinity on agriculture

The high salt concentration of the soil interferes with the osmotic processes by which plants absorb water and nutrients. Simultaneously, sodium, chlorine and boron ions accumulate in the plant, which simultaneously potassium and calcium are missing. The accompanying the salinization soil compaction complicates the growth of roots. With these effects a deterioration of the metabolism of soil organisms goes hand in hand.

Different crops are affected in varying degrees of salinization. Barley is considered the most resistant grain of salt and sugar beet are relatively resistant. Pineapple, apricot, citrus, apple, strawberry and peanut are considered particularly sensitive to salt.

Forms of salinization

Depending on the occurring minerals in the formation of typical ground forms.

Solonchak

The Solonchak (of sol = salt and chak = salty area ) is a typical Versalzungserscheinung with readily soluble salts. According to the World Reference Base for Soil Resources ( WRB ) Solonchak as solo power is a water -influenced soil and thus a typical phenomenon in incorrect watering. Worldwide, there are about 300 million ha Solonchak. Typically form in Solonchak in sinks slightly salt crusts, the floors are fixed and there is little biological activity in the soil instead.

Solonietz

Solo power (of sol = salt and etz = severe forms ) occurs on soils that are tonangereichert underground and have high concentrations of sodium. They are like the Solonchak to wasserbeinflussten soils according to the WRB. Worldwide, some 135 million ha are affected by this form of salinization. In these soils high pH values ​​( > 8.5) found.

Calcisol

The Calcisol heard as the Gypsisol to the salt accumulation soils ( WRB ). It is produced by precipitation of Sekundärcarbonat. Calcisols are estimated at about 1 billion ha worldwide. Here, secondary carbonate accumulates in deeper soil layers and the calcareous raw material is often no longer available.

Gypsisol

Gypsisol (of gypsum plaster = ) arises as the Calcisol. In contrast, but not accumulate carbonates at, but instead gypsum ( calcium sulfate). Of this form about 100 million hectares worldwide are affected.