Soil salinity is probably the most important issue although mono-cropping, without a fallow period, rapidly depletes the soil fertility. A reduction in organic content will contribute to a soil's erodability. The increased use of agro-chemicals, needed to retain productivity under intensification, can introduce toxic elements that occur in fertilizers and pesticides. On irrigated lands salinization is the major cause of land being lost to production and is one of the most prolific adverse environmental impacts associated with irrigation. Saline conditions severely limit the choice of crop, adversely affect crop germination and yields, and can make soils difficult to work.
Careful management can reduce the rate of salinity build up and minimize the effects on crops.
All such actions, which may be very costly, would require careful study to determine their local suitability. Figure 6 indicates the sensitivity of a range of important crops to soil salinity. Careful soil monitoring is highly recommended whenever the irrigated regime is intensified, even though the saline layers might be far below the soil surface and the irrigation water applied is of high quality. Unless there is some drainage from the scheme, whether natural or artificial, salinity problems will arise with consequent adverse impacts for agriculture. The accumulation of salts in soils can lead to irreversible damage to soil structure essential for irrigation and crop production.