30 BULLETIN 995, IT. S. DEPAETMEXT OF AGRICULTURE. 
should be applied. Under certain conditions commercial fertilizers 
do not seem to be effective. This may be due to the fact that 
the fertilizer elements are not used in the proper proportions, or it 
may be due to the physical condition of the soil. The greatest 
benefits are obtained from commercial fertilizers when the soil is 
well supplied with humus. There should, of course, be a suffi- 
cient supply of moisture in the soil to dissolve and hold in solution 
the plant foods that are already present or that may be supplied in 
the form of a commercial fertilizer. The benefits arising- from the 
use of fertilizers, whether stable manure, green crops, or mineral com- 
pounds, are frequently noticeable over a period of several years ; 
hence, in estimating the value of a fertilizer the results of several 
seasons* crops should be taken into account. 
CROP ROTATION. 
Occasionally a farm is found on which beets are grown on the same 
field year after year. "While this seems to give satisfactory results 
for a time in some instances, it is in general a poor method and one 
that can not be recommended, since it tends to encourage the de- 
velopment of certain sugar-beet pests which eventually render the 
crop unprofitable. The rotation practiced in the various sugar-beet 
areas must necessarily depend upon the crops that do best or are 
most profitable in these several localities, as well as upon the crop 
and live-stock requirements of the farm. In some areas, for example, 
the Irish potato is a profitable crop and forms an important link 
in a system of rotation with sugar beets. In other areas the Irish 
potato is not successful, and in such sections it would be a waste of 
time and money to undertake to utilize it in rotation with sugar 
beets. Again, there are areas in which the muskmelon is very satis- 
factory and rotates well with sugar beets or other crops: in other 
parts of the sugar-beet territory the muskmelon can not be grown 
with success. In planning the rotation, therefore, one must have 
in mind not only the crops that will rotate well with sugar beets. 
but also the success of those crops independently. The grower must 
also consider the practicability of handling such crops from the 
standpoint of his returns: for example, in some sugar-beet areas 
alfalfa oives o-ood vields, but because the hauls are so long the 
value of the alfalfa under normal conditions is not sufficient to pay 
the transportation charges and leave a reasonable profit. Therefore, 
unless there is an abundance of live stock to utilize the alfalfa locally 
or unless it is needed as a soil improver, it is not a satisfactory rota- 
tion crop in certain localities in spite of the fact that it produces 
satisfactory yields. Our studies of the various sugar-beet sections 
indicate that live stock is an important factor in crop rotation on the 
sugar-beet farms. As already indicated, certain crops can be grown 
