20 BULLETIN 512, U. S. DEPARTMENT OF AGRICULTURE. 
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 Inlets; Screens about /24o07 below Top of Terraces 
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Fic. 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 
practically 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 a 
the slope, due to such little erosion as takes place between the terraces, i 
can be prevented: from accumulating above the terrace by proper 4 
methods of plowing and cultivation; that is, by frequently throwing t 
the soil up the slope with the plow and by planting and cultivating 3 
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- P 
fall, and erosive action is thereby reduced to a minimum. i 
The question arises often as to what becomes cf the water above 4 
the terrace and whether it remains sufficiently long on the surface si 
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 
