858 



SCIENCE 



[N. S. Vol. XXXIX. No. 1015 



SOIL EEOSION AND ITS SEMEDT BY TEB- 

 BACING AND TBEE PLANTING-^ 



Peoples have the habit of visiting their 

 heaviest penalty — death — upon those offenders 

 who imperil the life of the community. For 

 example, horse-stealing among cowboys, de- 

 stroying bridges among the Caucasus moun- 

 taineers. By the same reasoning the time is 

 approaching when the permitting of gullying 

 and soil erosion will rise in our minds from 

 waste to offense and finally to crime. 



Soil erosion is an irreparable waste, per- 

 haps the only irreparable waste, when in an 

 age of science one considers the great possi- 

 bility of substituting one substance or com- 

 modity for another. Once the soil is gone, it 

 is gone, and can not be returned. In locations 

 of shallow soils underlaid with rock, a very 

 small amount of erosion throws land out of 

 agricultural use for a geologic epoch. 



Owing to our vast resources and cheap land 

 and the scientific nature of erosion control, 

 little has thus far been done to check erosion 

 either prohibitively or constructively. An- 

 other reason why we have done or appreciated 

 so little in this field is that the problem is 

 relatively new to the Teutonic peoples. 



I. FACTORS TENDIXG TO AGGRAVATE AND INCREASE 

 SOIL EROSION IN AMERICAN AGRICULTURE 



1. Relation, of Agricultural to Nature's Ero- 

 sion Control. — Nature controls erosion with 

 plant roots, so that in most of the United 

 States the problem scarcely existed before 

 white men's agriculture began here. The 

 beginning of agriculture here was not merely 

 the introduction of an old-established method. 

 American agriculture is unlike that of Europe 



1 Section I., of the A. H. A. S., has a eommittse 

 on soil erosion. This committee appointed J. Eus- 

 sell Smith, Ph.D., professor of industry in the 

 Whaiton School of Finance and Commerce, Uni- 

 versity of Pennsylvania, a subcommittee to gather 

 information as to the relation of tree crops to the 

 erosion problem. This paper presented at the 

 1913 meeting of the section is the result of jour- 

 neys of investigation in the Mediterranean coun- 

 tries and islands and in central and southern 

 United States. 



and far more deadly as a promoter of erosion. 

 European agriculture has but little bare 

 ground, most of the crops covering the entire 

 surface of the ground and holding it with a 

 root mass, as does wheat, barley, clover. 

 America has added to the European agricul- 

 ture the three great bare-ground crops of corn, 

 cotton and tobacco. The tillage of these crops 

 prepares the ground for erosion. The soil is 

 kept bare, loose and soft. Frequent cultiva- 

 tions gash it ready for the starting of the dig- 

 ging rills of running water when a storm 

 comes. 



2. The New and Erosive Type of Rainfall. — 

 Another factor, new to the Caucasian race, is 

 a heavy summer rain which exists in all the 

 territories growing these three crops, and 

 comes in the peculiarly destructive form of a 

 thunder shower, with its tremendous powers 

 of eroding loose bare soil. 



3. The Increasing Area of Erosion-inducing 

 Crops. — The increasing demand for these bare- 

 ground crops tends more and more to make 

 us cultivate and destroy hilly lands which, 

 while in good pasture or forests, erode but 

 little. 



n. FACTORS IN EROSION CONTROL 



1. Deep plowing has been extensively recom- 

 mended by our agricultural authorities, but 

 casual observance of hiU lands almost any- 

 where shows it to be but a partial remedy, and 

 com and cotton fields under the best recom- 

 mended deep plowing can often be shown to 

 be eroding at rates that are completely ruin- 

 ous if kept up for any long period. 



2. Contour plowing tends to diminish ero- 

 sion, but this device is hostile to the American 

 system of farming that is characterized by the 

 utilization of machinery sweeping in straight 

 lines over large areas. 



3. Terracing has been quite widely used in 

 the south, but usually in a relatively inefficient 

 way because in effect it chops a field up into a 

 multitude of small fields of irregular shape. 

 Between these little patches are untilled banks 

 that grow weeds instead of crops. We have, 

 however, the recent discovery of the Mangum 

 terrace worked out by a fanner at Wake 



