94 FOR BETTER CROPS IN THE SOUTH 



tile from thirty to thirty-two inches deep. It is never advisa- 

 ble to allow tile to be less than eighteen inches below the surface. 



Distance Between Tile Lines — The distance between the 

 lines of tile varies with the depth that the tile is laid, which is 

 determined by the nature of the soil. When the tile are placed 

 shallow, the lines must be put close together and vice versa. 

 The distance apart varies from thirty-five to 180 feet. Experi- 

 ence will teach what is best in individual cases. 



The Grade to Use — By the grade we mean the fall per 

 hundred feet. This is often expressed in feet, but may be 

 expressed satisfactorily in inches. Generally speaking the size 

 of the tile should be increased with the lessening of the grade. 

 We have seen a case where the tile lines were laid perfectly level 

 for several hundred feet, and gave good satisfaction, but in this 

 case, the required velocity of the water was gotten by the excess 





The depth oi the tile effects the width of area drained 



of fall from the laterals and from the main line above. Also, 

 in this particular instance, the tile was sixteen inches in 

 diameter. Smaller tile would probably not have given good 

 results. A fall of two to four inches per hundred feet will give 

 good results with tile from four inches and up, providing the 

 tile line does not exceed 800 or 1,000 feet in length. For shorter 

 lines, less grade may be used, and in case of longer lines, larger 

 size tile should be used. Remember you can never get too much 

 grade. 



Selecting the Tile — In purchasing tile it is well to see to it 

 that they are vitrified but not glazed. The ends should be 

 squarely cut, and it is extremely important that the inside 

 should be smooth and free from roughness. Table 1 shows the 

 size of tile used for different areas of land when the fall is known. 

 For instance, if we have one foot fall in one hundred feet, four- 

 inch tile will drain 11.9 acres, six-inch tile will drain 33.1 acres, 

 etc. This will assist you in selecting the size of tile to use. 



