DRAINAGE AND IRRIGATION 29 



the tiles are not draining they are filled with air so that there 

 may be a circulation of air through the soil by way of the 

 tiles. Another advantage in having the land drained is that 

 it permits the farmer to get out crops earlier in the spring, 

 and since the drained land is warmer they grow faster. So 

 the farmer with drained land generally raises bigger crops 

 and gets more returns from his land. Drained land is always 

 easier to plow and to cultivate, so that such soil is tilled with 

 less labor. 



How to Drain. — Before beginning to drain a piece of land 

 the farmer should look it over carefully to determine where 

 the drain is to empty and in what places lines of tile are to 

 be laid. Large areas should be surveyed. Generally there is 

 one main line of large sized tile put through the lowest place 

 in the field where the most water naturally runs. This line 

 is called the main. Into the main from the sides run branch 

 lines of smaller tile. These branch lines are called laterals. 

 The slope of the land toward the place where the drain is 

 to empty, or the outlet, is called the fall. This should be at 

 least two or three inches per one hundred feet, and five 

 to eight inches is considered about the best average. Larger 

 tiles are generally used near the outlet than toward the upper 

 end of the drain. The tiles in the laterals are not so large as 

 those in the main. The size of the tile depends upon the 

 extent of the system, the amount of water to be carried, and 

 the fall. Professor Elliott, in Farmer's Bulletin 187, says that 

 the tiles in the laterals should be 3 or 4 inches in diameter and 

 that a 5-inch main (and its laterals) having a length of 1,000 

 feet and a fall of 3 inches per 100 feet will drain 25.1 acres. 

 In a complete farm system of drains 2-inch laterals would be 

 ample. The depth to which the tiles are put is not always the 



