22 BULLETIN 462, U. S. DEPARTMENT OP AGRICULTURE. 



nearer the inlet side of the box, making the chamber on the outlet side large 

 enough to admit the hand easily to operate the plugs. For this purpose cypress 

 plugs are often used. One of these consists of a large hollow plug fitted to the 

 opening and a smaller solid plug which fits the hole in the larger plug. By 

 this arrangement different sized streams can be obtained. The plugs often 

 become water-soaked, making it difficult to remove them. Sliding galvanized- 

 iron gates would be preferable. 



The tools used in excavating and installing the tile are shown in figure 3 of 

 Plate II. The mattock and ax are used for cutting the roots in the newly 

 cleared land. The wide irrigation shovel is used for removing the topsoil and 

 the curved adjustable shovel for cleaning out and forming the bottoms of the 

 trenches. 



The cost of the Sanford tile system ranges from $100 to $125 per acre, not 

 including the water supply or drainage outlet from the field. 



In the operation of the Sanford system water is turned into the main feed 

 pipes and divided among a number of laterals by operating the intake plugs. 

 The plugs in each pocket are adjusted so that the water will be backed up in 

 certain sections and held there until the moisture meets between the tile lines. 

 The water issues from the tile joints into the porous sandy subsoil and follows 

 along on top of the impervious substratum until the surface-soil area is under- 

 lain with a sheet of water. If irrigation continues after this state has been 

 reached the water will soon show on the surface. 



Irrigation is begun when the first winter crops are planted in the fall. The 

 ground is completely saturated to the surface to settle the young plants into 

 place and give them a start. The common practice is to irrigate every 10 days 

 to 2 weeks during the growth of the crop, depending upon the rains which occa- 

 sionally occur during the winter season. Celery is irrigated 24 hours before 

 cutting. This is thought to swell the plants and make them brighter and 

 heavier. 



The length of time required to saturate the Sanford soils varies greatly on 

 the different farms. Some farmers use a large head from a number of wells, 

 forcing the water into both ends of level laterals, thus causing saturation within 

 a few hours. Others use smaller amounts of water and take 12 to 48 hours to 

 irrigate. The amount of moisture contained in the soil prior to irrigation and 

 the depth to hardpan determine materially the length of time necessary for 

 saturation. It also takes longer to subirrigate a field on which a cover crop 

 has been turned. Likewise, a soil finely pulverized is slower to irrigate than 

 one that has not been cultivated. 



Overirrigation is a common practice, and probably is more expensive than 

 is commonly realized. On opening the tile lines to drain off the excess water 

 large quantities of the fertilizing constituents applied in commercial fertilizers 

 are carried away. This has taught the farmers in this section the need of 

 applying fertilizers immediately following a heavy rain. 



There are special cases about Sanford deserving of mention which 

 have not been touched upon in the above discussion. Systems for the 

 subirrigation of the fields adjacent to the river which have heavy 

 grades should be laid out somewhat differently from those described 

 above. If the mains were laid on the high side of the field and the 

 laterals allowed to run down the slope having a grade of several feet 

 per hundred, the water would not have sufficient opportunity to per- 

 form its task of irrigating the ground between the lines. In such a 



