26 BULLETIN 995, U. S. DEPARTMENT OF AGRICULTURE. 



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 production 

 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 some- 

 times reached or exceeded, and beet growing becomes unprofitable. 

 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. 



SOIL FERTILITY. 



Elements of plant growth. — By fertility 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 cannot be said to be fer- 

 tile. 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 par- 

 ticular 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 kStates) 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 



