CHAPTE-R X Vl 



SOIL EROSIOF 



Soil Erosion a Serious Problem. — Soil erosion is commonly 

 understood to mean the washing away of soil by water. On 

 comparatively level areas this problem is not of much importance. 

 In general, however, it has become most serious. Hundreds of 

 thousands of acres of farm lands in the United States have rolling 

 topography, and because of neglect in proper management, im- 

 mense soil losses have occurred through hillside washing in every 

 state of the Union and in almost every county of every state. It 

 has been estimated that in the United States 4,000,000 acres of 

 farm lands have already been ruined by soil erosion, and nearly 

 twice as much more greatly damaged. This loss in terms of dollars 

 amounts to millions annually. 



Injuries Resulting From 'Erosion. — ^Land ruin is the most 

 serious effect of soil erosion. Other injuries are: Much of the soil 

 reserve of plant-food elements is washed away; much damage 

 is done to irrigation; water power is lost; it interferes with naviga- 

 tion; and it interferes in farm management (Fig. 188). 



The loss of plant-food elements caused by erosion is due to the 

 removal of organic matter and the j&ne soil particles. This is 

 clearly shown, in the following analyses of two soils collected on 

 the same farm — one sample was collected from the hilltop and the 

 other from the cropped flat, or ^^ creek bottom,^' below. 





Organic Matter 



Nitrogen 

 per cent- 



Phosphorus 

 per cent. 



Soil from hilltop 



Soil from creek bottom. . . . 



Low 

 High 



012 

 025 



0.04 

 0.08 



These data show clearly that the soil removed by erosion is 

 the richest part of the land. This makes the erosion problem all 

 the more serious- Indeed, it has been estimated that every year 

 there is in the United States an unnecessary waste from soil erosion 

 of more than 400,000,000 tons of soil material — an amount greater 

 than that removed in digging the Panama Canal. ^ Much of this 



1 United States Department of Agriculture Yearbook, 1916. 



283 



