Soils salinization

In arid environments, where the soluble products of weathering are not completely removed from the soil, saline solutions may circulate in the soil as well as in rock fractures. If upon evaporation the salt concentration increases above its saturation point, salt crystals form and grow (Goudie et al, 1970). The growth of salt crystals in crevices can force open fractures. Salt weathering occurs in cold or hot deserts or areas where salts accumulate. Boulders, blocks. 

Table 1. Effect of soil salinity of the yield of various crops ...

Total porosity Percentage large pores Soil salinity Soil sodium content Humus content... 

In cherozems of Serbia, soil boron is in the range of 25-40 mg/kg. The average B content is 30 mg/kg. Boron content increases with salts in arid soils. Saline salts and saline alkali soils contain 40-65 mg/kg total B. 

McLaughlin M.J., Tiller K.G., Beech T.A., Smart M.K. Soil salinity causes elevated cadmium concentrations in field-grown potato tubers. J Environ Qual 1994 23 1013-1018. 

Thus, P may not have a larger impact on phytodiversity than other nutrients per se, but can gain it due to its availability relative to other resources. This explains also why the relation between P and phytodiversity may be overruled easily by other factors, e.g., management factors like heavy grazing (Hill et al. 2005 Dorrough et al. 2006) or environmental factors like soil salinity (Theodose and Roths 1999). 

The yield of a crop irrigated with saline water is related to its salinity tolerance, such that once the threshold of tolerance is exceeded, the yield will decline. The following relationship derived by Mass and Hoffman (1977) shows this decrease in yield as soil salinity exceeds the threshold salinity for a species of plant ... 

Figure 6.1 is a plot of relative crop yield versus soil salinity, and shows the regions for classifying crops based on their salinity tolerance. The crop yield for barley is indicated by the dashed line, with its crop yield indicating that it is tolerant to soil salinity. 

Fig. 6.1 Classifications of crop tolerance based on relative crop yield versus soil salinity. The tolerance of barley is shown by the dashed line. Adapted from Maas (1985) and Maas and Hoffman (1977)...

Increases in soil salinity can hinder the growth of plants by limiting their uptake of nutrients (Grattan and Grieve 1992). The major cations that affect saline soils are Na", Ca ", Mg ", as well K", while the major anions are CP, SO4, HCOj" and NOj". When the soil has a high pH, COf is also present. The nutrients which plants require most are Ca ", Mg " and K". However, the uptake of and Ca " is hindered by the presence of excess Na", and an increased concentration of Ca " in the soil can lead to a deficiency of Mg " (Grattan and Grieve 1992). 

Corwin, D., Rhoades, J., Simunek, J. Leaching requirement for soil salinity control Steady-state versus transient models. Agric. Water Manag. 90(3), 165-180 (2007)... 

Soil salinization is the first stage of environmental destruction caused by sahnity and is related to river and lake salinization. For example, the diversion of the Amu Darya and Syr Darya Rivers caused significant desiccation of the Aral Sea, but it also caused salinization of associated agricultural land (e.g., Funakawa et al. 2000 Spoor 1998). In Australia, soil salinization is the most severe environmental problem on the continent, causing dramatic changes in landscape, industry, and the future of farmland (e.g., Dehaan and Taylor 2002). 

Keywords Soil, salinity, frost phenomenon, molar volume fractions... 

The only section in the regulations that concretely deals with salinity (section 4.1.11) states that Soil salinity, acidity and sodicity levels, where relevant, shall be actively managed so as to prevent long term soil degradation. Management priority shall be such as to include reparation and regeneration of lands so affected. Details of plans and actions shall be outlined in the OMP where such issues are noted as of concern. Details as to how this can be achieved are not given and overall the issue seems of low priority. 

Newton, P.J., Myers, B.A., and West, D.W., Reduction in growth and yield of Jerusalem artichoke caused by soil salinity, Irrig. Sci., 12, 213-221, 1991. 

Irrigate by methods that reduce evaporation (i.e., avoiding sprinkling and flow in ditches), but do not increase local soil salinization. 

The U.S. Soil Salinity Laboratory Staff (1954) reported that SAR values of 10-15 (mmol L )1/2 usually correspond to ESP values in the range of 10-15 at which values clays will undergo dispersion. This relationship may vary among colloids with different mineralogy (Oster et al., 1980) and/or mixtures of colloids with different mineralogy (Arora and Coleman, 1979). Consequently, the force by which given types of colloidal particles attract or repulse each other in a Na-Ca or Na-Mg solution is a function of the total concentration of the salt, the type of divalent cation (Ca or Mg), and SAR. Therefore, pH, salt concentration, type of divalent cation, and SAR are expected to play important roles on soil colloid flocculation. 

The presence of salinity in soil and water can affect plant growth in three ways (1) it can increase the osmotic potential and hence decrease water availability (2) it can induce specific-ion effects by increasing the concentration of ions with an inhibitory effect on biological metabolism and (3) it can diminish soil-water permeability and soil aeration by adversely affecting soil structure. The adverse effects of soil salinity on plant growth and productivity varies with the type of plant being grown. 

Keren, R. and I. Shainberg. 1984. Colloid properties of clay minerals in saline and sodic solution. In I. Shainberg and J. Shelhevet, Eds. Soil Salinity Under Irrigation—Processes and Management. Springer-Verlag, Berlin, pp. 32-47. 

Shalhevet, J., P. Reineger, and D. Shimshi, 1969. Peanut response to uniform and non-uniform soil salinity. Agron. J, 61 384-387. 

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