JAMAICA. 



BULLETIN 



OF THE 



BOTANICAL DEPARTMENT. 



Vol. VIII 



New Series.] MAY, 1901. 1 ' _ x 



Jr£trt 0. 



WASHED SOILS : HOW TO PREVENT AND RE- 

 OLAIM THEM.* 



THE EROSION, OR WASHING, OF AGRICULTURAL SOILS. 



The denudation, or washing, of lands of the higher levels of the 

 earth's surface is a process which no human precaution can wholly pre- 

 vent. It has been one of the most important forces and factors in the 

 geological changes which have so modified the surface of the earth. 

 The present surface of the largest portion of the United States is 

 made up of this " sedimentary" or " drift" material which has been 

 moved from the place where it was formed through the disintegration 

 and decay of the old crystalline rocks, by water, wind, or moving ioe, 

 and which has accumulated to a depth of hundreds or thousands of 

 feet over nearly the entire surface of the c< untry. It is estimated that 

 the general surface of the land in the area of the crystalline rocks of the 

 Piedmont Plateau has been lowered at least 2,000 feet by this contin- 

 ual washing. This vast amount of material has been slowly removed 

 and deposited elsewhere by the very same agents which we are con- 

 tending with to-day in our gullied fields ; for this denudation, or ero- 

 sion, is still going on, as it has been for ages past. 



As a rule this denudation is exceedingly slow and the general level 

 of large tracts of country is not lowered more than an inch or two in a 

 hundred years. Where the change is as slow as this it is undoubtedly 

 of benefit to the human race, as in the course of time it must carry off 

 the soil which has been used over and over again for vegetation and 

 expose fresh material to the roots of plants. With this slow change 

 the natural forces are amply sufficient for the decay of the subsoil and 

 for the conversion of this freshly exposed materiel into a good soil. 

 Whon the rate of denudation is excessive, however, and more rapid 

 than the natural decay of the subsoil material which is exposed, it 

 may work serious injury to agricultural lands. 



Along the banks of the Ohio River and in very many portions of the 

 South hundreds of fields that were once covered with sturdy forests of 

 oak, maple, walnut, and pine, and which bore under cultivation, after 

 *,U. S. Dept. of Agriculture : Farmers' Bulletin No. 20. 



