SOIL EEOSIOlSr IN^ THE SOUTH. 21 



is either covered ^^-ith a layer of sand or is scoured into ditches and 

 smaller channels, impairing the agricultural value of the land. 



In some of the districts of the South the gullies, which are ordi- 

 narily dry, become filled with rapidly flowing water. This temporary 

 stream carries a heavy burden of soil material, much of which is sand, 

 as the soil conducive to the formation of these gullies is generally 

 sandy. The velocity of the water is first checked in the valley 

 and the sand is largely deposited. A formerly productive field 

 covered in this way with a layer of sand 6 inches to 2 feet in thick- 

 ness is shown in Plate IX. 



AGRICULTURAL PROBLEMS. 



As previously pointed out, the greatest damage from erosion gen- 

 erally occurs where the original growth has been removed and the 

 land in being used for crop production. This most frequently means 

 clean culture. The agricultural conditions in the South are espe- 

 cially favorable for erosion, as the main crop is cotton, which requires 

 entire freedom from grasses and weeds. The rotations practiced 

 may include some other clean cultivated crop, as corn, but in a great 

 many cases cotton is the only crop grown. 



The labor problem and other economic conditions have much to 

 do with this system of farming. Ordinarily the small farmer and 

 the tenant can obtain credit only by growing crops that can not be 

 easily disposed of without the creditor's knowledge. The crop that 

 meets all conditions best is cotton. Hence it oftens happens that 

 the same land is cropped year after year to cotton, until the soil be- 

 comes so unproductive that its cultivation is not profitable, when it 

 is allowed to ''he out," and becomes infested with weeds. It is then 

 that erosion is most destructive. The soil is exhausted of organic 

 matter, and even before the weeds begin to grow the rains form 

 gullies over the surface. Probably the field will not be put under cul- 

 tivation again, and in a few years it becomes devastated, without 

 agricultural value, and a menace to the surrounding land. 



The question of erosion must be considered in adopting crop rota- 

 tions. In addition to the use of terrace and hiUside ditches for check- 

 ing the soil wash, it must be remembered that the incorporation of 

 largo quantities of organic matter produces an open, porous sod, 

 capable of absorbing water, and that deep plowing furnishes a sub- 

 soil reservoir for the storage of smplus water. It is not always pos- 

 sible to practice these methods with certain crops, so that the ten- 

 dency to erosion and the effects of c(^rtain practices must bo con- 

 sidered before a given crop is included in the rotation. The Georgia 

 experiment station,' for example, has conducted experiments which 

 indicate that plowing Ixilow S inches lessens the yield of cotton. 

 It is also known that tlie (piality of tobacco is injured by legume 



> Oa. Agr. Expt, Sta., Bui. 03, p. 124. 



