Changes in Composition of Irrigated Soils as Related to the Quality of Irrigation Waters
1954
Thorne, D. W. | Thorne, J. P.
These studies were conducted to determine the effects of field application of waters of different quality on the chemical composition of soils. Soil samples were obtained from paired sites within irrigated and unirrigated soil areas located in 14 different soil locations and representing use of 12 different irrigation waters. The data for irrigation water and soil composition were statistically analyzed for regression and correlation relationships. The salt content of the soils was found to be closely related to the salt content of the irrigation waters. The percentages of exchangeable sodium in the soils had significant regressions on sodium percentages, weighted sodium percentages, sodium adsorption ratios and the theoretical equilibrium exchangeable sodium percentages for the irrigation waters included in the study. The regressions of exchangeable sodium percentages on excess sodium percentages of the waters were not significant. There were significant negative regressions between increase in lime content of the irrigated soils (calcium carbonate content of irrigated soil minus calcium carbonate content of non-irrigated soil) and the electrical conductance, the chloride content, calcium and magnesium content and sulfate content of the irrigation water. Lime tended to be leached out of soils when the electrical conductance of the irrigation waters exceeded 2 millimhos per cm. and frequently to increase in soils irrigated with waters of lesser salt content. The data do not indicate that the carbonates and bicarbonates in irrigation waters studied contributed significantly to either the accumulation of carbonates in soils or to increase in exchangeable sodium percentages.
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