SOURCE: http://www.fao.org/docrep/R4082E/r4082e08.htm

Most crops do not grow well on soils that contain salts.

One reason is that salt causes a reduction in the rate and amount of water that the plant roots can take up from the soil (see Fig. 105). Also, some salts are toxic to plants when present in high concentration.

Some plants are more tolerant to a high salt concentration than others. Some examples are given in the following table:

The highly tolerant crops can withstand a salt concentration of the saturation extract up to 10 g/l. The moderately tolerant crops can withstand salt concentration up to 5 g/l. The limit of the sensitive group is about 2.5 g/l.

SOURCE:http://uwacadweb.uwyo.edu/eppl/Plant_Pathology/factsheets/sheets/Wy988.pdf

Symptoms of salt injury in plants resemble drought. Both conditions are characterized by water stress (wilting)and reduced growth. Severe injury caused by prolonged exposure or high salinity results in stunted plants and tissue death. Reduced growth caused by salinity is a progressive condition that increases as salinity increases above a plant’s tolerance threshold.

Plants vary in their response to soil salinity. Salt tolerant plants (plants less affected by salinity) are better able to adjust internally to the osmotic effects of high salt concentrations than salt-sensitive plants. Salt-tolerant plants are more able to absorb water from saline soils. Salt-sensitive plants have a limited ability to adjust and are injured at relatively low salt concentrations. Many horticultural and landscape plants are classified as sensitive or moderately sensitive to soil salinity. Specific plant tolerances are affected by climate, soil conditions, cultural practices, and variety selection. During cool weather when plant transpiration demands are low, salt injury

will be less than during hot, dry weather. There is wide variation in salt tolerance among varieties or rootstocks of some species. Salt tolerance during germination and emergence, though not well defined, is often less than that given for mature plants. A good example is beets. Beets, a moderately tolerant plant, are more sensitive at germination than corn, a moderately sensitive plant. Practices to reduce salinity in the seed zone, such as leaching before planting and planting on the sides of sloping beds, can be used to improve germination and emergence. For ornamentals, size and appearance are the important criteria for determining salt tolerance. Comparisons based on growth reductions may not be completely applicable. In some cases, tolerances are based on the premise that reduced growth may be acceptable as long as plants appear healthy and attractive. Soil salinity is difficult to overcome. Salts can be removed from the soil by leaching if drainage is not restricted. Watering plants more frequently can reduce salt injury. Adverse effects of soil salinity can also be reduced by promoting vigorous growth through good management and adequate fertility. If you suspect soil salinity is a problem, contact your university extension educator

SOURCE: http://peanut.tamu.edu/library/pdf/SoilSalinity-01.pdf

As soils become more saline, plants become unable to draw as much water from the soil. This is because the plant roots contain varying concentrations of ions (salts) that create a natural flow of water from the soil into the plant 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. Each plant species naturally contains varying levels of root salts. 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. .

SOURCE: http://www.waterforlife.net.au/agriculture/reduce-soil-salinity

Soil salinity is one of the most serious agricultural problems. The cause of this process is the accumulation of salts in soil capillaries leading to a sharp decrease in plant fertility. Salt concentration left in plant capillaries, with insufficient amount of nourishing substances leads to plants dying.

Plant growth and yield are limited mainly by the soil environment factors. Soil, water, nutrients, salinity, sodicity, structure, temperature, pH, and mineral toxicities can all interact to limit plant growth. In Saline soils although pH (<8.5) and ESP (<15%) are not high, CEC is >4 mmhos/cm and an excess of soluble salt in the subsoil restricts water uptake by crops; in the case of alkalinity there are Nutrient deficiencies (either because of a lack of nutrients, or because roots are unable to access them). The best way of understanding these limitations is to consider them in terms of the interacting factors that directly influence crop growth.

SOURCE: http://www.ext.colostate.edu/pubs/crops/00503.html

Salinity problems are caused from the accumulation of soluble salts in the root zone. These excess salts reduce plant growth and vigor by altering water uptake and causing ion-specific toxicities or imbalances. Establishing good drainage is generally the cure for these problems, but salinity problems are often more complex. Proper management procedures, combined with periodic soil tests, are needed to prolong the productivity of salt-affected soils.

Excessive soil salinity reduces the yield of many crops. This ranges from a slight crop loss to complete crop failure, depending on the type of crop and the severity of the salinity problem.

Although several treatments and management practices can reduce salt levels in the soil, there are some situations where it is either impossible or too costly to attain desirably low soil salinity levels. In some cases, the only viable management option

is to plant salt-tolerant crops. Sensitive crops, such as pinto beans, cannot be managed profitably in saline soils. Table 4 shows the relative salt tolerance of field, forage, and vegetable crops. The table shows the approximate soil salt content (expressed as the electrical conductivity of a saturated paste extract (ECe) in dS/m at 25 degrees C) where 0, 10, 25, and 50 percent yield decreases may be expected. Actual yield reductions will vary depending upon the crop variety and the climatic conditions during the growing season.

Fruit crops may show greater yield variation because a large number of rootstocks and varieties are available. Also, stage of plant growth has a bearing on salt tolerance. Plants are usually most sensitive to salt during the emergence and early seedling stages. Tolerance usually increases as the crop develops.

The salt tolerance values apply only from the late seedling stage through maturity, during the period of most rapid plant growth. Crops in each class are generally ranked in order of decreasing salt tolerance.

SOURCE:http://www.cabi.org/gara/FullTextPDF/2009/20093019433.pdf

SOURCE: http://www.cabi.org/gara/FullTextPDF/Pre2000/19931974999.pdf

SOURCE: http://cmg.colostate.edu/gardennotes/224.pdf

High salt levels can reduce water uptake by plants, restrict root growth, cause marginal burning of the foliage, inhibit flowering, limit seed germination, and reduce fruit and vegetable yields. Irregular bare spots in gardens and uneven crop growth suggest salinity problems. Crop yields may be reduced as much as 25% without any damage being apparent. Salt injury generally is more severe during periods of hot dry weather, when water use is high. Sensitivity to soluble salts differs among plant species/cultivars and also with their state of growth. Seed germination and seedling growth are more sensitive to salt stress than mature plants.

SOURCE: http://extension.psu.edu/vegetable-fruit/fact-sheets/Soluble%20Salts%20in%20Soils%20and%20Plant%20Growth.pdf

SOURCE:http://www.annalsoftropicalresearch.com/pdf%20file/full%20papers/Asio%20et%20al.pdf

This process can be observed in low-lying coastal areas of the country due to salt water intrusion and the use of saline water to irrigate agricultural fields. Philrice (2001) reported that salinity has become a widespread constraint to rice production in most parts of the country. Salinization-prone coastal lands are estimated at 0.4 M ha of which 0.2 M ha is considered severely salt-affected. Places with considerable saline areas are cagayan valley, bicol, Iloilo, Palawan, negros, samar, Leyte and surigao. Over extraction of ground water in coastal areas for household and agriculture uses is also expected to increase the areas affected by salinization. rising sea level due to global warming will also increase the problem of sea water intrusion in low lying coastal areas throughout the country.

SOURCE:http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/127259/Managing-saline-soils.pdf

Salinity is the amount of salt in the soil or water. The dominant salt in most saline soil is common salt—sodium chloride (NaCl). Varying amounts of calcium, magnesium and potassium chlorides and sodium sulfates can also occur.

It is important to know the level of salinity. This determines:

• the types of plants that will grow in the soil, and their yield potential

• the characteristics of a soil

• the quality of water for irrigation, domestic, industrial and stock use

• the extent of the problem.