The Effects of Secondary Soil Salinization :: Agriculture Agricultural Essays

access Irrigation has been used as tool by humans for over 8000 years. Irrigation started in the Nile valley where humans attempted to modify the way that the river seasonally fill their fields in order to make cropland more productive (van Schilfgaarde, 1994). From 1940 to 1989 the join of land being irrigated around the world has increased 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 bountiful increase in land under irrigation occurred at the same sequence as an exponential jump in human population, and increases in some(prenominal) are greatest in the arid and sub-arid regions of the Earth. Our population has therefore bugger off reliant on irrigation to fend off large scale crave (Abrol et al., 1988). As rain falls it carries no dissolved salts. Once this peeing strikes the earth and travels as surface runoff or in account water it go out come into contact with and carry dissol ved salts. any water used for irrigation carries ions in solution and by depositing this water on our fields in the form of irrigation we can effect the concentration of salts in our croplands. If these salts become too concentrated it can lead to salinization. Salinization can decrease yields in its earliest stages and eventually lead to the destruction of fertility in the soil. Currently the Earth is losing 3 ha of arable land a minute to the effects of salinization (Abrol et al., 1988). Can we stop this loss? Will we be able continue using arid lands to meet our food require? The Secondary Salinization Process Salinization has a direct effect on both coiffure growth and the structure of the soil. If the soil is saline a plant will have to expend energy bringing water into its cells because it is oblige to work against osmotic potential. The cation exchange complex (CEC) effects the stability of colloid coat particles in the soil. The cations positive focus will be attracte d 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 in concert that Van Dehr Wahls forces will cause the clays to flocculate, or form stable aggregates. Sodic soils, whose CEC is dominate by mono-valiant sodium cations, will tend to be dispersed and non form stable aggregates.