diminishing of fertility-. • There is, however, a discrepancy between the 

 amount taken from the soil and that returned which may finally bring 

 about absolute 'depletion in some of the elements unless scientific 

 methods are enforced by the tillers of the soil. 



The farmer, therefore, is confronted with these two problems : First, 

 to make available plant food elements which exist in the atmosphere 

 and in the soil, and, second, to return to the soil plant food and guard 

 against wasting. The first problem involves several important opera- 

 tions, namely: 



(a) Drainage to carry off surplus water, and to admit atmospheric 

 oxygen to the seed-bed. 



(b) A well-plowed, thoroughly-pulverized and compact seed-bed. 



(c) A liberal supply of live humus. 



(d) A sufficient quantity of lime to prevent soil acidity. 



(e) Water in the subsoil in quantities to supply the needs of growing 

 plants and to have the connection between the bottom of the seed-bed 

 and the subsoils in such a physical condition that capillary attraction 

 will not be interfered with. 



(f) Rotation of crops. 



Sources of Plant Food 



In discussing the second problem, we will not attempt to offer 'any 

 plan to maintain the original plant food content of all the lands of the 

 globe, but will make a few suggestions with the view of maintaining to 

 a high degree the fertility of our tillable soils. 



How can we prevent the store of plant food in the seed-bed from 

 becoming less and less with the removal of each succeeding crop? 

 What can the farmer do? 



We know that oxygen is necessary to make combinations or com- 

 pounds of the plant food elements. 



We know that oxygen exists in the air in unlimited quantities and 

 that thorough tillage and proper drainage will place it where it is 

 required. 



We know that three-fourths of the entire atmosphere is composed of 

 nitrogen, an element which cannot be dispensed with in plant growth. 



We also know that the legumes, plants which can be grown in any 

 latitude where vegetation survives, are equipped with bacteria upon the 

 roots possessing the power to take this valuable element from the 

 atmosphere and deposit it in the soil. 



We know that carbon-dioxide, the product of decomposed animal 

 and vegetable matter, also exists in the atmosphere, and that from it we 

 can secure a sufficient amount of carbon to furnish most of the sub- 

 stance of the plant. 



