16 
plowing, however, is a necessity. The subsoil, upon standing, be- 
comes closely compacted, and heavy rains and walking over the 
surface greatly increase this tendency. Consequently it is neces- 
sary to replow at frequent intervals. In many localities the aeration 
is restricted to a layer a few inches in depth near the surface and nitri- 
fication scarcely ever becomes active. Deep plowing will permit the 
absorption of a much larger percentage of heavy rains, thus greatly 
reducing erosion and storing up much larger amounts of moisture 
for drier seasons. Most of the soils that are cultivated in pineapples 
become hard and closely compacted within a few months after 
planting. Consequently it is necessary to plow as deeply as possible 
between crops. 
Subsoiling has not been extensively practiced, but deep plowing 
should be the rule in all sections. The subsoils are not very different 
from the soils, except in some of the rainy sections like Olaa, and, 
after being acted upon for a short time by weathering influences, 
seem to be equally as fertile as the surface soil. In the drier sections 
deep plowing encourages deeper root development, thus tending to 
enable the crop to withstand drought. Successful soil management 
in Hawaii, therefore, requires deep plowing, followed by frequent 
shallow cultivation. 
INJURIOUS EFFECT OF PUDDLING. 
Great care and intelligence must always be exercised in plowing 
and tilling clay soils. The clay particles are extremely small and 
tend to settle down between the coarser grains, thus clogging the 
pores. However, the fine particles can be made to unite into granules 
by the judicious handling of the soil. In the natural state carbonic 
acid formed from the decomposition of vegetation and aided by evapo- 
ration causes the smaller particles to coalesce into granules, which 
then act as if the particles themselves were coarse. In this condition 
a heavy clay soil may be well aerated and fertile. On the other 
hand, tillage, in times of too great moisture, breaks up the granules, 
producing a puddled condition which is very difficult to bring back 
into a state of granulation. 
During the early stages of the cultivation of sod lands the bacterial 
processes bring about a rapid decomposition of the vegetable matter, 
which causes the clay to become granulated. After a few years, 
however, the organic matter has been so completely decomposed 
that the clay is easily puddled under the ordinary operations of cul- 
tivation. A single cultivation of such soils when they are wet causes 
serious puddling. The pineapple growers in the Wahiawa district 
have greatly injured their lands by cultivating too soon after rains. 
Much of the so-called exhaustion of Hawaiian pineapple soils is trace- 
able to wet cultivation. 
