Irrigation, Water and Soil Quality

Today, demographic expansion and the acceleration of urbanization forces farmers to use more and more “bad quality” water to irrigate, as waters of good quality must be reserved for drinking water supplies of the cities or industry, including touristic industry. This chapter introduces the key concepts concerning soil-water interaction. Irrigation waters are generally surface, spring, river or phreatic waters. Alkalinity is negative only in very particular geochemical conditions, those that lead to the production of sulfuric acid through sulfide oxidation. The soil solution is the mandatory intermediary of exchanges between plant, soil and atmosphere. Alkalinity is the basis of proton balances. Mineral fertilizers added are potassium and phosphate fertilizers. Geochemical models enable checking minerals/solution equilibria. The preservation of deep groundwater resources, few or none of which are renewable, and more generally water economy and good quality water economy, imply an integrated approach to the critical zone.