276 Bacteria in Relation to Country Life 



Among the forces that compel a tribute from land to 

 sea, the soil bacteria stand out prominently as busy 

 workers in the achievements of great results. Under 

 their touch, the inert mass of organic remains becomes 

 less inert, it yields copious amounts of the gas, carbon 

 dioxid. This, in its turn, becomes the key that helps to 

 unlock the mineral plant-food in the rock fragments. 



It is necessary that in this change from the insoluble 

 to the soluble state certain losses occur, for the reason 

 that the growing crop cannot take up all of the soluble 

 food. The sea claims and receives its tribute from the 

 store of this unused plant-food. It would be unjust, 

 however, to condemn the soil bacteria for their too in- 

 tense activity. In order that the crops may have enough 

 available food, more than enough must be produced. 

 It is for the farmer to decide whether more or less of 

 that excess is to be wasted from the land. 



SOIL BACTERIA IN RELATION TO LIME AND MAGNESIA 



Of all the rock ingredients in the soil, lime and mag- 

 nesia are, perhaps, most readily affected by the activities 

 of bacteria. The work of the latter constitutes a con- 

 stant drain on the lime resources and, to a lesser extent, 

 on the magnesia resources of the soil. Where vegeta- 

 tion is luxurious and bacteria are abundant, as is almost 

 invariably the case in limestone regions, the plant 

 remains decay rapidly and the limestone rock fades 

 away in the presence of the carbon dioxid produced. 

 Layers of limestone, 10, 20, or 30 feet thick, are some- 

 times reduced to a few inches of soil; canons, caves and 



