270 Bacteria in Relation to Country Life 



by exposing the bare fields modified by implements of 

 tillage, to the action of sun, wind, and rain. It is now 

 known that the same purpose can be accomplished in 

 these soils by liming and by the additions of large quan- 

 tities of organic matter. Objectionable weeds may be 

 eliminated in the careful cultivation of a hoed crop. 



The use of bare fallows may result in considerable 

 injury to the land on which the soil is rather light. The 

 frequent stirring and more thorough aeration intensify 

 the decomposition of the humus by stimulating the 

 chemical and bacteriological transformations. Such 

 intense changes, leading, as they do, to the accumula- 

 tion of available plant-food in the soil, involve possible 

 losses from leaching. They form, therefore, the strongest 

 argument against bare fallows, not only for sandy soils 

 or sandy loams, but also for clay and clay-loam soils. 



Fallowing and plant-food. — It has been proved by 

 experiments that fallowing is not an economical pro- 

 cedure from the standpoint of plant-food. The com- 

 paratively large amount of nitrates accumulated during 

 the fallow period is apparently retained only in part 

 for the succeeding crop, the remainder being washed 

 into the drains. The differences would be even more 

 striking on soils hghter than those upon which the 

 experiments were made. This view is further supported 

 by the fact that the benefits arising from fallowing were 

 least apparent at these fields in seasons of abundant 

 rainfall, when proportionately and absolutely greater 

 amounts of nitrates were removed in the drains. 



The benefits of fallowing, therefore, in so far, as they 

 arise from the larger supply of plant-food, are secured 



