902 
lished. Some silt is washed out through 
the tile, and tiny streamlets are formed 
leading to the joints of the tile. A dense 
clay holds its pores almost full of capil- 
lary water, which is not subject to perco- 
lation. With this condition the drain 
must be near the surface and function 
chiefly as a surface drain. Deeper drains 
are necessary in orchards, irrigated fields 
and all deep rooting crops. In general it 
is not desirable to lower the water table 
as far in sand as in clay, because there 
is less capillary action in the former. 
Place tile on the boundary of sand and 
clay if this is from two to four feet be- 
low the surface. This allows the water 
to move io the tile through the sand. 
Generally three to five feet will be suffi- 
cient depth, and three and one-half is the 
common depth The rule in the reclama- 
tion service in draining alkali land is 
to never place the tile more than four 
feet below the surface. 
Frequency or Distance Apart 
The distance apart is closely related to 
the depth. It also depends on the tex- 
ture of the soil and the amount and rate 
of the removal of rains. 
1. Relation of Depth and Distance 
Apart—If tile placed three feet deep and 
100 feet apart lowers the water table one 
foot from the surface at the highest 
point, then placing tile four feet deep 
will lower the water half-way between 
them, two feet below the surface. We 
could accomplish the same thing by plac- 
ing the tile 50 feet apart and three feet 
deep. If we put the tile deeper it will 
draw the water further each way, and the 
tile can be laid less frequently. 
2 The Amount of Raw and the Time 
Allowed for Removing It—Water moves 
through clay very slowly, and if a large 
amount is to be removed in a short time 
the drains will necessarily be placed close 
to the surface, and at frequent intervals 
their function will be primarily as sur- 
face drains. 
3. Influence of Soil Texture.—In clay 
the interval must be much less than in 
sand King found that 48 hours after 
a heavy rain the water table was one foot 
higher in clay soils at a distance of 27 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
feet from the drain. In sand the grade 
was one foot in 175 feet. Then to remove 
the water table to within one foot of the 
drains in clay, the tile lines would be 
placed every 54 feet, while in sand the 
distance would be 350 feet. This is 
probably the extreme, and the tile would 
need to be larger with this greater dis- 
tance. Impermeable soil will require fre- 
quent parallel drains where level. Use 
the regular, thorough system of drains 
where level, uniform soil is to be 
drained. The aim should be to reduce 
the water table a definite distance in a 
reasonable time after rains, and the 
drains must be sufficiently frequent to ac- 
complish this. 
The natural system removes water 
where it has accumulated in low places. 
Large areas are drained by single lines 
of tile. The tile follows the natural 
water course, or is placed so as to inter- 
cept the seepage. This will do where the 
aim is to secure only fairly perfect drain- 
age, so nearly sufficient for ordinary 
crops that the increased returns will pay 
a fair return for the outlay. 
Where in doubt, one could adopt the 
minimum interval and place the first line 
of tile at two or three times this interval 
If necessary, other lines could be placed 
between these at a later date. 
Experience with different soil condi- 
tions has given us a fairly definite dis- 
tance for placing tile in given soils: 
100 feet to 90 feet apart for sandy soils. 
60 feet to 75 feet apart for loam soils. 
50 feet to 60 feet apart for sandy loam. 
40 feet to 50 feet apart for loam, 
35 feet to 40 feet apart for heavy loam. 
30 feet to 40 feet apart for heavy clay. 
30 feet apart for soils high in iron and 
clay. 
Size—The size of the tile depends on: 
1. The amount of rain. 
2. The rate of removal. 
3g. The amount of surface run-off. 
4. The grade. 
5. The soil. 
6 
. The area drained. 
There are times when the crop has 
taken the moisture out of the ground 
so that a two-inch rain will not start the 
tile. At other times it may be necessary 
