Transient Changes in the Soil‐water System from Irrigation with Saline Water: II. Analysis of Experimental Data

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Abstract
Twenty‐three lysimeters containing four soil types with alternate wheat (Triticum aestivum L.) and sorghum (Sorghum vulgare Pers.) crops were irrigated with three synthesized levels (2.2, 3.9, 7.1 mmho/cm) of irrigation water. Salt balance was calculated from soil salinity sensor electrical conductivity EC measurements by determining a relationship between solution EC and solution concentration using a chemical equilibrium model. Solution samples and saturation extracts were taken to determine ion balances, and exchangeable cations were measured after the third crop.All methods of determining salt balance showed the order of 50% salt precipitation over the first 500 days of the experiment, approximately two times the expected amount when root zone salt concentrations have reached steady state. Release of Ca2+ ions from exchange sites and subsequent enhanced gypsum and CaCO3 precipitation was assumed to be responsible for the difference between transient and steady‐state behavior.The drainage composition of a lysimeter which had moved one pore volume through the root zone showed that only Cl‐ was approaching a steady‐state value. Exchange effects and enhanced precipitation were assumed to be buffering the concentration of the other ions.Water uptake in all lysimeters is occurring primarily in the top 20 cm, a consequence of high irrigation water salinity and daily irrigation.