Evaluation of Soil Salinity Leaching Requirement Guidelines.

Irrigation guidelines that were established several decades ago were based on steady-state conditions and are still widely used to assess the suitability of water for irrigation. Recently, high speed computers have facilitated the development of transient-state models that potentially can more accurately predict the chemical-physical-biological interactions in agricultural systems. A workgroup was appointed to review the development of steady-state analyses and transient-state models to determine if the current recommended guidelines on leaching requirements need to be revised. The Workgroup concludes that the present guidelines based on steady-state analyses over estimate the negative consequences of irrigation with saline waters. This error is particularly large at low leaching fractions. This is a fortuitist finding because it provides for a more efficient use of limited water resources and increases the feasibility of using saline waters.