216 THE SOILS AND CROPS OF THE FARM. 



2. A ton of clover hay contains more nitrogen than 

 does a ton of timothy hay, or corn fodder, or even 

 a ton of corn or oats. Nitrogen being the most ex- 

 pensive of the "precious" elements, the manure pro- 

 duced from clover hay is more valuable than that pro- 

 duced from the other food material. 



3. A crop of clover leaves in and on the soil 

 a larger quantity of vegetation than does the cereal 

 crops. This organic matter contains a large quantity 

 of the precious elements, which become available with 

 the decay of the vegetation. The land is thus in 

 a more suitable condition to grow a succeeding crop 

 than if the crop had not been grown. Grass crops 

 also leave a considerable quantity of vegetation be- 

 hind them, sometimes a greater quantity than the 

 clover plant, but usually not so rich in the precious 

 elements. 



4. It seems to be satisfactorily determined that 

 through the agency of the clover plant the free but 

 inert nitrogen, which constitutes about four-fifths of 

 the atmosphere, may be converted into active nitrogen ; 

 that is, it may become combined with oxygen. 



The virgin fertility of the soil was largely due to 

 the nitrogen combined with organic matter. This fer- 

 tility has been collected through countless ages. The 

 cloverplantis an agency through which this fertility 

 may be in a measure maintained. The clover plant is 

 only the indirect source of this beneficent property. The 

 direct power of converting atmospheric, nitrogen into 

 an available form for plant food lies in certain low or- 

 ganized plants called microbes or bacteria, which arc? 

 found in the root tubercles of clover plants. These 

 tubercles are characteristic of the plants of the clover 

 family. 



