Fallows Exhaust Plant-Food 271 



at the expense of the dormant constituents. Fallowing 

 from this standpoint is a means for hastening the spolia- 

 tion of the land and is wasteful in that it allows a con- 

 siderable proportion of the nitrates to escape into the 

 drains. It is surely more rational to occupy the ground 

 with some cover-crop during the portion of the year 

 when the main crop is not growing. 



The cover-crop secures the plant-food that becomes 

 available and. transforms it into organic material which 

 undergoes decay more rapidly than the old humus. If 

 the cover-crop belongs to the legume family, the ad- 

 ditional advantage is secured of utilizing atmospheric 

 nitrogen and storing it up in the soil in the crop residues. 

 Provision is thus made for restoring from time to time 

 the losses of humus and nitrogen, and for maintaining 

 the soil in a good physical condition. Fallowing, on the 

 other hand, hastens the burning up of the humus and 

 the depletion of the nitrogen and, in time, makes it 

 necessary either to abandon the soil to weeds or to seed 

 it down to grass. After remaining in an undisturbed 

 condition for some years its store of humus and of nitro- 

 gen becomes greater again and bare fallows seem to 

 yield, once more, profitable returns. 



This was the plan followed in olden times and it is 

 still followed in many localities. Many of the so-called 

 abaijdoned farms in the older portions of the United 

 States are again being placed under cultivation and are 

 yielding fair returris. The years during which they 

 remained untilled permitted them to gather a small 

 store of easily decomposed organic matter and made a 

 portion of their mineral constituents more available. 



