34 THE HxiXDBOOK FOR PRACTICAL FARMERS 



Types of drainage. — There are two general classes of drain- 

 age: (1) Open drains; and (2) under drains. Any channel or 

 opening which joermits the removal of the excess water in a soil 

 is a drain. It ma}^ he an open ditch or canal so small as that 

 made Avith a shovel plow, or it may be as large as a river. It 

 may he an nndergronnd channel maintained by poles or brush 

 or straw or stone or boards in the form of a box, or in tight clay 

 it may be an unwalled opening made by a mold plow. On the 

 other hand, it may be an opening nicely graded and carefully 

 arranged in a system of more or less parallel channels lined with 

 short sections of clay or cement pipe or drain tile, and finally, 

 where there is a rather thin, impervious strata on w^hich water 

 is held and below Avhich is a porous strata, such as gravel, sand 

 or a porous rock, drainage may be provided by means of a well 

 dug, drilled or formed by an explosive through the impervious 

 layer down to the porous strata. This latter is verticle drainage 

 applicable to only a very limited area of land. 



One's choice of these different methods of drainage must be 

 guided by the conditions of soil and rainfall, the area of land, 

 volume of water, grades and other features with which he has 

 to deal in a particular case. It is usually unwise to attempt to 

 follow any set rules for drainage. One should study the par- 

 ticular conditions at hand, consider the underlying principles 

 involved and proceed accordingly. A great many conditions of 

 wet land can be worked out by the average farmer with such 

 facilities as he may have at hand. 



Beneficial effects of draining*. — But why, it may be asked, is 

 proper drainage of the soil so fundamental to good soil manage- 

 ment? First of all, remember that practically all of the crops 

 ordinarily cultivated are accustomed to grow in soil in Avhich is 

 distributed sufficient free air to meet the needs of the roots for 

 their proper functioning. Roughly, this amount is represented 

 by a well-drained soil in good tilth. As an}^ farmer knows, the 

 tilth or physical heart of the soil is linked up with its moisture 

 condition. Therefore, in enumerating the benefits of drainage, 

 we may start Avith its effects on the physical condition or tilth 

 of the soil. (1) Reasonable drainage is the first recpiisite to the 

 maintenance of that fine friable granular condition of soil known 

 as good tilth. Wet soils, if clayey, are usually lumpy when dry. 

 Otherwise, they are very compact and impervious. (2) Good 

 tilth results in a larger pore space in Avhich to store available 

 moisture and necessary air for the roots. It means better and 

 deeper ventilation. This results (3) in deeper root penetration. 



