Date of Award:

5-1956

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Irrigation and Soils

Committee Chair(s)

H. B. Peterson

Committee

H. B. Peterson

Abstract

Considerable experimental evidence supports the concept that the growth of plants generally decreases progressively as the salt concentration of the substrate increases, but certain relationships between plant and substrate are still not fully understood. The chemistry of salt toxicity to plants involves many interactions both as to the quantity and kind of ions presented to the roots and those accumulated in the plants. Many plant species have shown sensitivity to excess accumulation of specific salts frequently encountered in saline soils. Thus Eaton (1942), Wadleigh, Hayward, and Ayers (1951) have shown most of the fruit trees to be susceptible to injury as a result of the accumulation of chloride ion. Wadleigh, et al. (1951) have reported orchard grass to be sensitive to calcium salts. Recently, Brown, Wadleigh, and Hayward (1953) have found calcium chloride more toxic to some fruit trees than isosmotic levels of sodium chloride. These and other studies have indicated a greater influence of specific ions than of the osnotic pressure of the solution.

The failure of crops in a given saline soil may be due to a variety of factors. Moreover, the relative importance of the contributing factors may be difficult to assess. For example, the deleterious effects of osmotic pressure per se or of individual elements are unknown. Also, the relative importance of high concentration of calcium salts, or the inaccessibility of essential elements induced by the presence of sodium, is far from being quantitatively related to growth inhibition observed in random situations.

The present system of salt tolerance evaluation of crops is based on the use of equal proportion of calcium chloride and sodium chloride in artificially salanized plots. This basis is, however, open to question for the real evaluation of calcium-sensitive plants. Specific sensitivity to chloride and calcium is being emphasized inasmuch as previous investigations have indicated the possibility that poor salt tolerances of some legumes and cereals may be related to accumulation of those ions in the plant tissues.

In view of the extreme importance of these questions in connection with the proper evaluation of salt tolerance of some of the important forage plants, the research here reported was devoted to the evaluation of some of these contributing factors as single entities.

A quantitative study was made of the specific effects of high concentrations of calcium chloride and sodium chloride on ionic absorption by the plants adequately supplied with nutrients to make consistently satisfactory growth.

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