120 THE FARMER OF TO-MORROW 



periment station has been established at Man- 

 dan, North Dakota, to try out the imported 

 varieties, that the Great Plains may again be 

 wooded. What became of the forests that 

 once covered the region is one of the baffling 

 mysteries which scientists have not solved. 



As to the former fertility of the bench 

 lands, it is at least partially explained by the 

 fact that at one time the waters of the present 

 Gulf of Mexico extended as far north as the 

 confluence of the Mississippi and the Missouri 

 Rivers; the land of cotton extending south of 

 this point at the present time having been 

 built by deposits of alluvium during subse- 

 quent periods. An upheaval, resulting in the 

 formation of plateaus and mountains in the 

 Southwest, causes the moisture-laden winds of 

 the Gulf at the present day to veer to the 

 north; otherwise the Great Plains w r ould to- 

 day be a land of rain and the fertile bottoms 

 of the Mississippi River valley would be strug- 

 gling with the problems of dry-land agri- 

 culture. 



Soil fertility depends not only on the min- 

 eral elements in the soil, but equally upon 

 complex organic compounds, the result of de- 

 caying vegetable matter. The reserve fer- 



