20 



BULLETIN" 512, U. S. DEPARTMENT OF AGRICULTUKE. 



be laid along the upper side of the terrace and made to discharge into 

 the main drain laid down the center of the depression or gully. 

 Where stone is available an inlet may be made by filling a section 

 of the trench to within 1 foot of the surface with loose stones. This 

 will facilitate greatly the entrance of the surface water. This prac- 

 tice can be followed also on the tile lines laid down the gully, thus 

 eliminating the objectionable drop inlets which interfere with farm 

 operations. In addition to removing the surface water through the 

 soil and thereby eliminating surface erosion many other benefits re- 

 sult from the practice of tile drainage. 



In planning a system of broad-base level-ridge terraces it is de- 

 sirable, though not necessary, that the terraces end at natural drain- 

 age channels. In the absence of such channels they may end at 

 property lines, fence rows, or timbered areas. Cooperative agree- 



(Drop /n/efS; Screens oiouf /zfoof 6e/otv Top of Terraces^ 

 >s*}!%v Terracs 



Fig. 9. — Method of removing water impounded behind terraces in a gully. 



ments between neighboring landowners for extending a terrace 

 system from one farm to another so that the terraces shall terminate 

 at natural drainage channels would result in increased effectiveness. 



Where the system of broad-base level-ridge terracing is employed 

 joractically all the fertile particles of soil and the accumulated humus 

 are retained on the surface, and, by proper methods of farming, the 

 fertility of the land is built up from year to year rather than worn 

 out through soil losses. The small amount of soil that moves down 

 the slope, due to such little erosion as takes place between the terraces, 

 can be prevented from accumulating above the terrace by proper 

 methods of plowing and cultivation ; that is, by frequently throwing 

 the soil up the slope with the plow and by planting and cultivating 

 the crop rows on level ridges. The result is that each square foot 

 of land surface tends to drink up the maximum amount of the rain- 

 fall, and erosive action is thereby reduced to a minimum. 



The question arises often as to what becomes of the water above 

 the terrace and whether it remains sufficiently long on the surface 

 to sour the land or injure the growing crop. Experience shows that 

 the natural drainage of open soil on hill lands ordinarily is so rapid 

 that a deficient supply of moisture for crops results and the land is 



