Also, excess sodium under conditions of low salinity and especially high pH can promote slaking of aggregates, swelling and dispersion of soil clays, degrading soil structure and impeding water and root penetration. Some trace constituents, such as boron, are directly toxic to plants. Over the course of history, thriving civilizations declined in part due to their inability to sustain food production on lands that had been salinized. Many of these problems are caused by excessive use of water for irrigation due to inefficient irrigation distribution systems, poor on-farm management practices, and inappropriate management of drainage water. Inefficient on-farm irrigation practices cause local salinity problems.
Local problems increase as a result of poor on-farm drainage.
Excessive irrigation increases salt loading in water tables and downstream aquifers which causes regional salinization. Lack of local and regional drainage systems results in lands being put out of agricultural production. In the future, global food needs will continue to increase while the soil and water resources available for new crop production will be limited and of diminished quality. The need to protect soil resources as well as to conserve water will continue to increase. Water must be utilized more efficiently and its quality protected.