1. A manometric technique for the assessment of soil aeration, described in a preceding paper by Webley (1947), has been used for comparing the effects of the incorporation into soil of alginic acid (as the ion) and other organic materials on soil airwater relationships. Some of the shortcomings of the technique, as well as its advantages are described.

2. The addition of sodium alginate to a soil improves its crumb stability and its water-holding power. It is shown that the addition of 0-1 g. sodium alginate to 100 g. of the air-dried standard soil used in this work has a gross effect equivalent to an increase in the water-holding power of soil of 11%. The effect of the alginate rapidly increases to a maximum with increase of the concentration of the alginate. The incorporation of the relatively insoluble calcium alginate has but little effect on the soil airwater relationship. It is suggested that alginate confers hydrophilic properties on soil by its combination as an ion with one or more constituents of the soil particle, thereby presenting new surfaces with high water-holding powers.

3. Incorporation into soil of cellulose acetate, methyl cellulose or of carboxymethyl cellulose improves its water-air relationships.