IRRIGATION IN FLORIDA. 23 
situation the main line should run down the steep slope while the 
lateral should lead off perpendicularly or nearly so, following 
approximately the contours and having a very slight grade, as in the 
case of the level grounds. 
Instead of a main line of terra-cotta pipe some farmers use an 
open trough or flume, letting water into the laterals by removing 
wooden plugs from the side of the flume and damming the water in 
the flume by check gates. When this method is used water does not 
percolate from both sides of the tile lines but runs one way only, or 
down the grade from one lateral to the other. This method, while 
used in other parts of Florida as well as at Sanford, is not so satis- 
factory in very dry weather as is the subirrigation of the level lands, 
some of the farmers having great difficulty in getting the water to 
the surface. 
Another special method used to some extent in Sanford is irriga- 
tion without the use of a head main feed line. In this case the lateral 
tiles are laid perfectly level and are fed from an open ditch which 
also serves as the waste or drainage ditch in times of excessive rains. 
This method is somewhat of a makeshift, but works very well, and 
can be used for a while in this form when the farmer can not afford 
a heavier outlay. Sometimes the farmer will use this method and lay 
the tiling double distance, filling in the additional lines after he has 
grown a crop. The double spacing does not work so well for irriga- 
tion but will answer as a temporary expedient and at the same time 
drain the land, which in many cases probably is of more importance 
than the irrigation. 
Concrete tile was used almost exclusively for laterals in the early 
development of Sanford subirrigation. Eecently, however, concrete 
tile has been mostly replaced by burned clay tile, as the concrete 
broke down after having been in the ground a few years. The dis- 
integration of the tile probably was due to the use of materials un- 
adapted to the making of a good concrete and to improper methods 
of manufacturing and curing the product. Cheapness was sought 
at the expense of quality, and a very porous tile was produced which 
gave great opportunity for soil acids to attack the structure. 
The most necessary condition for successful subirrigation is a 
porous surface soil overlying an impervious substratum, which is the 
formation found in the Sanford section, as shown by Plate I, figure 1. 
The topsoil is a porous, light-colored sand, while the subsoil is a dark- 
colored hardpan which holds the water until it has spread laterally 
through the sandy topsoil. If subirrigation of high pine land with 
a clay subsoil 8 to 10 feet below the surface is attempted, the chances 
are that water could be run in the tile a month without any ap- 
preciable effect on the surface soil. Several attempts have been made 
