Drainage Required to Manage Salinity

The amount of drainage required to prevent loss in crop productivity from excess soil salinity has been termed as the leaching requirement (Lr). Steady‐state models for predicting Lr are reviewed and compared with experimentally measured values. Values of Lr predicted from the exponential model, which computes the average soil salinity in the root zone based upon an exponential pattern of crop water uptake, correlated best with measured values. Acceptable estimates are also obtained with a simplified model that approximates an average soil salinity based on values for the top and bottom of the root zone. The highest correlation coefficient was 0.67, indicating that none of the models is completely satisfactory.