24 BULLETIN 995, TJ. S. DEPARTMENT OE AGEICEXIVEE. 
ditches will run lengthwise of the field, thereby avoiding the crossing 
of the ditch in the usual farming operations. The size and depth of 
the open ditch will depend upon the length and fall of the ditch, 
the location of the subsoil, the amount of water to be carried, and 
the position of the outlet. The drainage ditch should always be deep 
enough to prevent any interference of the water table with the crop 
to be grown. 
The blind ditch. — The most satisfactory method of artificial drain- 
age is the blind ditch. In the construction of this ditch tile is used 
most commonly. Many fields that otherwise would not yield profit- 
able crops have been reclaimed by the blind ditch. These ditches 
should be laid out very carefully with reference to direction, depth, 
and slope, so that the entire area under consideration will be drained 
thoroughly. The size of the tile is very important. Tiles that are 
too small must never be used. This is false economy, and it fre- 
quently results in added expense in that the small tiles must be taken 
up and replaced with larger ones. The tile should be large enough to 
carry off the water quickly in times of excessive rainfall, deep enough 
not to be disturbed by the plow or other implements, and laid so 
carefully that the ends will fit against each other evenly and a gentle 
and continuous fall should be provided, without depression or ele- 
vation. The outlet of the blind ditch should be kept open, that the 
water may flow freely. 
SEEPAGE. 
Seepage is closely related to drainage. Many fields or areas that 
otherwise might be profitable for crop production are rendered use- 
less by seepage. This is especially noticeable in those areas where 
irrigation is practiced. Seepage is detrimental to the soil in several 
ways : (1) As a loss of water, especially in cases where water has been 
stored for irrigating purposes, and (2) through a loss of the use of 
the land, either because the soil is too wet for crop production or be- 
cause of the accumulation of soluble minerals which are brought to 
the surface through seepage. The injurious soluble minerals usually 
are known as alkali. 
Seepage from streams. — Some streams are so located naturally 
that a portion of the water seeps into the adjacent soil, form- 
ing marshes or waste places due to excessive moisture : this is 
especially true where the fields adjacent to the stream are low. 
level, or underlain with an impervious subsoil. The nature of the 
bank of the stream is of importance in this connection. If the 
overflow at flood time is prevented by the construction of dikes the 
land may be made productive by drainage. Usually these marsh- 
lands when drained are very fertile and produce good crops, though 
they are not always the best for sugar-beet production, since they 
sometimes produce large roots low in sugar. 
