PLANT INDUSTRIES 327 
with increased rapidity. In so doing it carries away large 
quantities of soil, sometimes uncovering the burned roots 
until the trees are easily overturned by winds.! 
There are several means of preventing much of this loss of 
soil by erosion. In wooded regions judiciously cutting part of 
the timber each year, rather than cutting all of it at once, 
gives opportunity for new plants to occupy and hold the soil. 
There are many kinds of soil-holding plants which, if properly 
placed, will prevent erosion in its earliest stages, and these 
should be used. In open, hilly fields which are exposed to ero- 
sion, grass and meadow crops are desirable, since their roots 
help to hold the soil throughout the whole year. In such 
cases the roots and stems help to prevent the rapid run-off 
of the surface water. The very things that need to be done 
in the cultivation of plants increase the danger of loss of soil 
where rapid flow of the surface water cannot be prevented. 
In hilly fields it is often difficult, sometimes impossible, to 
prevent erosion. In some localities the rows of growing plants 
are arranged across the slope of the hill; this arrangement 
helps somewhat in retarding the surface flow of water. If culti- 
vation is continued in such places, the soil sooner or later be- 
comes eroded, and it is with extreme difficulty that any plants 
gain a foothold fig. 240). In some foreign countries hillsides 
have been saved for cultivation by a process of terracing. 
The terraces are constructed in such a way that the soil upon 
each is level or slopes toward the hill, thus retarding or pre- 
venting erosion. Such terraced farms are sometimes most cesir- 
able for vineyards, but it is obvious that for ordinary crops these 
elaborate processes of terracing, and the constant care required, 
will prove profitable only where available land is extremely 
scarce. In many localities where the slope of the surface is 
moderate enough, underground drains may be laid to take care 
of the surface flow and thus prevent erosion except at times of 
extremely heavy rains. 
1 The Movement of Soil Material by the Wind,’’ Bulletin 68, Bureau of 
Soils, U.S. Dept. Agr., 1911. 
