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. Recently, 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 



