46 THE FERTILITY OF THE SOIL [CH. 



continuous wheat cultivation, practised under modern 

 conditions in new countries. When the virgin land 

 is first broken up its fertility level is high ; so long as 

 it remains under cultivation this level can no longer 

 be maintained, but rapidly runs down. During the 

 degradation process considerable quantities of plant 

 food become available and a succession of crops can 

 be raised without any application of manure. In fact 

 there is commonly more plant food than the crop 

 needs and addition of manure gives no crop increase. 

 Hence arises the idea that the land needs no manure, 

 and the pioneer, fully occupied with the pressing needs 

 of the moment, not only supplies none, but does not 

 even put back into the soil any part of what he takes 

 away. The grain is sold and the straw is either burnt 

 or dumped into gullies. After a time the unstable 

 period is over and the new equilibrium level is 

 reached at which the soil will stop if the old hus- 

 bandry continues. In this final state the soil is often 

 not fertile enough to allow of the profitable raising 

 of crops; it is now starving for want of those very 

 nutrients that were so prodigally dissipated in the 

 first days of its cultivation, and the cultivator starves 

 with it or moves on. 



"0 man, that from thy fair and shining youth 

 Age might but take the things youth needed not." 



Such is the history of many of the derelict farms in 

 parts of the United States and such must inevitably 



