Effects of irrigated agriculture on water and soil quality (case perimeter Guelma, Algeria)

In Algeria, more than 20% of irrigated soils are concerned by the problem of salinity. In the perimeter of Guelma, the results showed that the soils have low salinity despite of high electrical conductivity (1244 µS/cm) of irrigation water and increased organic matter, nitrogen, potassium, and phosphorus contents. It should be noted that the soils had exhibited higher salinity and low organic matter content before starting the irrigation in 1973. The reduction in the salt content is due to the leaching of salts from percolated water after the intensive irrigation; however, the increase in the content of organic matter can be explained by the accumulation of the organic matter transported by irrigation water, conditions of waterlogging, and types of crops (vegetable/cereals). As to the quality of groundwater, nitrate is the dominant nitrogen component entering groundwater and it is very alarming that by 45% of water sources (springs, wells, and boreholes) the nitrate contents are over 50 mg/l. It is a serious problem because it serves as a drinking water supply for the local population. Moreover, this water is highly mineralized (electric conductivity > 1000 µS/cm) because of the intensive use of artificial fertilizers and to the poor quality of water irrigation. The contamination by organochlorine pesticides is below the value admitted by the WHO for water resources. Endosulfan is the most dominant active ingredient with an average concentration of 0.066 µg/l.