PHYSICAL PROPERTIES OF HAWAII SOILS 23 
If the wilting coefficient is calculated by dividing the moisture 
equivalent by the Briggs and Shantz factor 1.84 (9, p. 5S), the figure 
25.3 will be obtained for the whole series. This average figure 
agrees well with experimentally obtained data. Hartung (19, p. 15), 
working with pineapples, noted that no root growth took place when 
the moisture content fell below 22.5 per cent. Feeble efforts at root 
development took place between 22.5 and 27.0 per cent moisture 
content. 
Farden (17, p. 157) determined experimentally the wilting coeffi- 
cient for three different soils on which pineapple plants were grow- 
ing, and obtained 23.6, 25.7, and 27.8; correlating these figures with 
the moisture equivalent, which was also determined, he calculated the 
factor, which he found to be 1.45, 1.4, and 1.46 — figures much lower 
than the Briggs and Shantz factor. Although the factor 1.84 is 
approximately applicable for an over-all average, the factor appar- 
ently varies considerably and must be determined experimentally 
for different soil types. However, the critical moisture point of 
Hawaii soils may safely be said to be about 25 per cent. This 
figure agrees well with results obtained in tests with Porto Kico 
and Cuba sugarcane soils. These soils, as is known, are somewhat 
similar to Hawaii soils, being red, laterites, and lateritic. Crawley, 
as quoted by Bennett and Allison (£, p. 307) observed that certain 
Porto Rico clay-land cane suffered where the soil contained 23.5 
per cent, and the subsoil 24.3 per cent of moisture. He was also 
of the opinion that " where the moisture in Cuban ' red soil ' is 
reduced below 25 per cent, cane will suffer." 
RELATION OF ORGANIC AND INORGANIC PROPERTIES TO 
ADSORPTION 
ORGANIC PHASE 
It has already been stated that in most cases the amount of organic 
matter present is the determining factor in the moisture relation- 
ships in Hawaii soils. It has been suggested as a possibility that 
all the organic matter does not exist in the clay or colloidal fraction 
of a mechanical analysis, and that a part of the organic matter, on 
account of the size of the particles, is present in the subdivisions of 
silt. Logically, it ma} 7 be supposed that the soil organic matter 
undergoing decomposition passes through different gradations in 
particle size before assuming colloidal dimensions. In these investi- 
gations all particles smaller than 0.002 millimeter in equivalent 
diameter are considered as colloidal. With the realization that this 
limit is an arbitrary one, it is reasonable to suppose that the organic 
matter shows adsorptive power before reaching this arbitrary limit. 
It may be argued that organic material existing in this coarser state 
is simply colloidal aggregates resisting dispersion, but for practical 
considerations they are particles of silt dimensions exerting their 
power of adsorption in that subdivision. Further, the organic matter 
is often stated to exist chiefly as coating around particles of colloidal 
dimensions, but it is reasonable to suppose that it also exists as coat- 
ing around the fine silt particles. Moreover, coarser particles of 
decomposing organic material may have a highly adsorptive coating 
