LONG-TERM SALINITY DEVELOPMENT IN A LYSIMETER EXPERIMENT

Over a period of 6 years, various crops were grown in tanks, filled wi th loam and clay, and were irrigated with water of three different lev els of salinity. A combination of soil water sampling, salt balance an d salt model was used to study the change in the composition of the so il water and the development of soil salinity. After 3 years an equili brium was attained in the exchange between soil water and adsorption c omplex. Precipitation of a mixture of calcium and magnesium carbonate occurred during the whole experimental period. During the last two cro pping periods the average chloride concentration of the soil profile o btained from soil water sampling was about twice as low as that obtain ed from the salt balance, due to preferential flow through macropores attaining the porous cups. Model calculation indicated a bypass fracti on of a about 0.15. The steady-stale leaching model of USSL could be u sed to estimate the long-term chloride concentration of the soil profi le. (C) 1997 Elsevier Science B.V.