The Effects of Secondary Soil Salinization :: Agriculture Agricultural Essays

Introduction Irrigation has been used as tool by worldly concern for over 8000 years. Irrigation started in the Nile valley where clements attempted to modify the look that the river seasonally flooded their fields in order to make cropland more than productive (van Schilfgaarde, 1994). From 1940 to 1989 the amount of land being irrigated around the world has increase at a rate of 2.7% per year. In 1940 there were 95 M ha in irrigation while by 1989 there were over 280 M ha (van Schilfgaarde, 1994). This commodious increase in land under irrigation occurred at the same time as an exponential jump in human creation, and increases in both are greatest in the arid and sub-arid regions of the Earth. Our population has therefore become reliant on irrigation to fend off large scale hunger (Abrol et al., 1988). As rain falls it carries no change state salts. Once this water strikes the earth and travels as surface runoff or in ground water it will come into contact with and extend d issolved salts. Any water used for irrigation carries ions in solution and by depositing this water on our fields in the piddle of irrigation we can work the concentration of salts in our croplands. If these salts become too concentrated it can steer to salinization. Salinization can reduce yields in its earliest stages and eventually lead to the devastation of fertility in the soil. Currently the Earth is losing 3 ha of arable land a minute to the rears of salinization (Abrol et al., 1988). Can we stop this passing? Will we be able continue using arid lands to fiddle our food needs? The Secondary Salinization Process Salinization has a direct effect on both plant growth and the structure of the soil. If the soil is salty a plant will have to expend energy rescue water into its cells because it is forced to work against osmotic potential. The cation exchange complex (CEC) set up the stability of colloid size particles in the soil. The cations positive charge will be attrac ted to the negative charge found on clay particles which make up most of the colloid fraction. Di-valiant cations(Ca, Mg) will allow the colloidal particle to get close enough together that Van Dehr Wahls forces will cause the clays to flocculate, or form stable aggregates. Sodic soils, whose CEC is dominated by mono-valiant sodium cations, will tend to be dispersed and not form stable aggregates.