900 
which lies in unsightly masses along the 
edge of the ditch will, in a year or so, 
assume a more workable shape and can 
be leveled down with the plow and 
scraper, until the land can be cultivated 
nearly to the edge of the ditch. It is 
always well, however, to keep a strip 
on each side bordering the ditch in grass, 
to prevent crumbling of the banks and 
loss of soil from the adjoining field. The 
space between the waste bank and the 
ditch is called the borm, and should equal 
the depth of the ditch. Water will flow 
with a fall of six inches to the mile, 
but to be effective the fall of a ditch 
should be from 4 to 6 feet. Large and 
deep ditches made straight and so con- 
structed that they will not receive silt 
or debris in large quantities will prob- 
ably be self-cleaning, are necessary for 
large areas, and should be from 6 to 10 
feet deep. 
In many cases the entire grade for 
lateral drainage must be made by addi- 
tional depth of the outlet. The velocity 
and carrying capacity of the ditch in- 
creases with the depth. Water eight feet 
deep will have twice the velocity of that 
one foot deep for the same width of ditch. 
This partly explains why shallow ditches 
make poor drainage outlets. 
Capacity 
The capacity depends on the area to 
be drained, the slope of land and the fall 
obtainable. See text for tables. 
Velocity of Discharge 
This is modified by the fall and a num- 
ber of other factors. A poor ditch with 
a rough bottom and irregular sides will 
carry only about half as much as a 
smooth, cement-lined canal. Grass and 
weeds will decrease the capacity to about 
one-fourth. The form of ditch is very 
important. 
Wetted Perimeter 
The sides and bottoms of the ditch 
touched by the water are known as the 
wetted perimeter. Friction varies direct- 
ly with this factor. The wetted peri- 
meter should be as small as possible in 
comparison with the cross section. 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
Disadvantages 
Open surface drains have several dis- 
advantages as deep soil drains, 
1. They are seldom of sufficient depth. 
2. They are apt to have a small carry- 
ing capacity, due to their uneven grade 
and rough bottom and sides. 
8. They are expensive to maintain. 
4, They waste much land. 
5. They greatly interfere with cultural 
operations. 
6. They may be subject to serious 
erosion. 
Covered or Underdrainage 
This is the only complete form of drain- 
age. Underdrains or any underground 
channels are constructed for the removal 
of water. Many kinds of materials have 
been used for this purpose, but in recent 
years they have been almost entirely sup- 
planted by tile. Brush, stones, boards 
and bricks were formerly used. Under- 
drainage will improve the soil wherever 
there is not complete natural drainage. 
Tile 
Tile is best for underdrainage because 
it is the cheapest, the most durable, the 
easiest to lay, and finally because it will 
drain the soil most quickly. Box drains 
will last from ten to twelve years. In 
draining the land with red tile use well 
burnt cylindrical tile. These tiles, one to 
two feet long, are laid through the soil in 
one continuous line with such a grade 
that all water which finds its way into 
them will be carried by gravity to the 
lower end of the line, thus carrying the 
surplus away. The water enters the 
openings at the ends, or joints as they 
are called. The ends of the tile are 
placed close together in order to prevent 
the soil from entering, yet none too close 
to prevent the water from entering 
The action of the tile drain in removing 
the surplus water from the soil is as 
follows: 
The drain being surrounded with soil, 
the spaces of which are filled with water, 
the water in the soil flows by gravity 
through the crevices in the ends of the 
tile and passes off more or less rapidly, 
according to the grade with which the 
tile is laid. Other water of the soil 
