The moisture equivalent of heavy soils

Abstract

(1) The moisture equivalent of a normal soil diminishes as the weight of soil taken for the determination increases.(2) Some soils are particularly impermeable to water in thick layers: in these cases the moisture equivalent increases with the weight of soil taken and may become very large owing to waterlogging. A soil may, however, have a very high moisture equivalent without showing waterlogging.(3) Dilute solutions of flocculating salts such as calcium sulphate, or ammonium nitrate or sulphate, reduce the moisture equivalent, and sodium carbonate increases it.(4) The effect of sodium carbonate is complicated: with gradually increasing concentration, the moisture equivalent first diminishes and then increases to a maximum, after which there is further diminution.(5) The soil samples which easily showed waterlogging in the Briggs-McLane apparatus had a higher concentration of hydroxyl-ions (pH) than those which did not.(6) Whilst the colloidal content of a clay seems related to its moisture equivalent, no such connection appears to exist for substances such as kaolin or aluminium hydroxide.

Some factors affecting the irrigation requirements of deciduous orchards

“…The rainfall during the winter of 1920 was only 8. 35 inches, a deficiency of 6.79 inches. This was a particularly severe season for the unirrigated rows.…”

The moisture equivalent of heavy soils. II

“…For clays separated and purified by similar methods, this ratio is closely associated with "clay" properties which enter so greatly into their water relationships. In some cases the moisture equivalent follows closely the composition, being highest with clays highest in silica: in other cases, the differences are more strikingly exhibited when the effect of heat or of alkalis on moisture equivalent is studied (3), or better, the imbibitional water content 1 . This constant shows a much better relationship with composition (and with clay-like properties) than moisture equivalent.…”