THE BEET-SUGAE INDUSTRY IN THE UNITED STATES. 25 
there must be more or less alkali dissolved in the water. As this 
water rises to the surface of the soil it brings with it the salts held 
in solution. After the water evaporates from the surface of the 
soil the alkali remains, and it may eventually accumulate to such 
an extent that crop production is greatly reduced or rendered 
entirely impossible. This condition is a limiting factor in the pro- 
duction of sugar beets as well as other crops in certain portions of 
the sugar-beet area. The sugar beet is one of the most alkali resistant 
of our farm crops, but even with this plant the limit of endurance 
is sometimes reached or exceeded, and beet growing becomes un- 
profitable. Alkali in the seed bed is especially troublesome, since 
the young plants are very tender and therefore susceptible to this 
and other adverse conditions. If the beet plants are well started 
before the alkali accumulates in the surface soil, much less damage 
will be done, as the subsequent growth of the plants is less affected 
by the same amount of alkali. The alkalinity of a soil may be 
reduced by the use of irrigation water, provided the irrigating water 
is comparatively free from alkali and a satisfactory drainage system 
has been established. 
FERTILITY. 
Elements of plant growth. — By fertility in this connection is meant 
the ability of the soil to produce a good crop. The difference between 
a rich soil and a fertile soil should be kept in mind — that is, a soil is 
rich if it contains a considerable quantity of each of the elements 
required by the plant in the process of growth. Unless, however, 
these elements are available to the plant and the physical conditions 
of the soil are such as to- promote plant growth, the soil can not be 
said to be fertile. If a single element required by the plant, though 
present, is not soluble, this condition will render the soil infertile. 
In order that an element may be available to the plant, it must be 
soluble, and it must dissolve rapidly enough to supply the plant with 
that particular element as rapidly as the plant requires it. Certain 
elements are always available when present ; other elements must be 
acted upon by certain substances under certain conditions in order to 
become available or soluble. It is apparent, therefore, that fertility 
is one of the limiting factors in the production of sugar beets as well 
as of other crops. 
The sugar beet requires the same elements of plant food that are 
required by other field crops, but in slightly different proportions ; 
for example, a 10-ton crop of sugar beets (which is approximately 
the average yield for the United States) will require about 30 pounds 
of nitrogen, 14 pounds of phosphoric acid, and 71 pounds of potash ; 
a wheat crop, yielding 20 bushels per acre, will require 41 pounds 
of nitrogen, about 13 pounds of phosphoric acid, and IT pounds of 
63212°— 18— Bull. 721 4 
