THE BEET-SUGAR INDUSTRY IN 1920. 31 



to advantage if there is an abundance of live stock to utilize them. 

 Even if certain crops could be sold from the farm at a reasonable 

 return above the cost of production, it would be poor policy to sell 

 them, for the reason that by so doing a large amount of plant food 

 would be shipped away. Live stock, if properly handled, enable the 

 farmer to keep a larger proportion of the plant foods on the farm 

 than could be done if the crops themselves were removed". Feeding 

 the crops on the farm is the best practice and will generally yield the 

 largest returns per unit of land and per unit of labor, especially if 

 the proper relations between crops, live stock, land area, and labor 

 are established. It is apparent, therefore, that several objects may 

 be accomplished by proper crop rotation, all of which must be kept 

 in mind in order to reap the greatest returns from the sugar-beet 

 farm. 



Effect on the soil. — As has been previously noted, all plants require 

 certain plant foods, and these elements are utilized by different plants 

 in different proportions. The rotation of crops insures a better 

 utilization of these plant foods than can be obtained by growing 

 a single crop. Certain crops are deep rooted, while others are more 

 shallow. The deep-rooted crops tend to stir the soil to a greater 

 depth and in this way make the plant foods more readily available 

 for the shallow- feeding crops. Certain crops aid in the production 

 of certain plant foods, as, for example, the leguminous crops store 

 nitrogen, which is rendered available to the other crops grown in 

 rotation with the legumes. Again, certain crops require more or 

 less cultivation, as is the case with sugar beets. This stirring of the 

 soil tends to expose the plant foods to the action of the elements, 

 thereby rendering the mineral material available for the use of the 

 beet plants and the plants of succeeding crops. 



Relation of pests to crop rotation. — The rotation of crops tends 

 to reduce or to destroy those pests which depend upon certain plants 

 for their existence. As is well known, some plant pests live and 

 thrive only on certain plants. If these plants are grown year after 

 year in the same field, they furnish favorable breeding conditions 

 for the propagation and increase of these pests. By changing to 

 other crops, plants upon which the pests can not live or upon which 

 they do not thrive may be grown and the pests thereby destroyed or 

 reduced to a minimum. Frequently the pests have resistant forms 

 or stages in which they can exist in a dormant condition for several 

 years, as is notably true of the brown-cyst stage of the sugar-beet 

 nematode and 1 the resting-spore stage of certain fungi. In such 

 cases it is necessary to plan the rotations with a view to starving out 

 these pests. To do this the rotations must be of such a length that 

 crops upon which these pests can not thrive may be grown for several 

 years in succession. In some cases other methods must be resorted 



