CHAPTER 61 



Farm Drainage and Irrigation 



Water is the first essential to plant growth, and yet either too much or 

 too little prevents a normal growth of most farm crops. The removal of 

 water from the soil is known as drainage, while the adding of water is called 

 irrigation. 



LAND DRAINAGE 



The need for drainage and the advantages of it are discussed in 

 Chapter 7. Only the engineering features of it will be discussed here. 



Co-operation. — Wherever large tracts of farm land are to be drained, 

 co-operation among the land owners is necessary for the establishment of 

 an economic drainage system. The laws of most states provide for an 

 equitable appraisement of benefits derived by the land owners in a drainage 

 district and make possible the establishment of the district when the 

 majority of land owners ask for it. 



The first step in the formation of a district is an accurate survey of 

 the natural water course and an estimate of the size and length of the 

 system of open ditches necessary for the proper drainage of the land. The 

 ditching is generally done by a contractor making a specialty of this kind 

 of work. His services are secured through the ditch commissioners, three 

 or more in number, who are elected by the land owners of the district. 

 Bids are usually let in order to secure competition and get the work done 

 at an equitable price. 



The dredged ditches, when completed, usually provide each land owner 

 with an outlet. All subsequent drainage is done by the individual owners, 

 each for his own farm. The individual farm drainage consists chiefly or 

 wholly of tile drains that empty into the open ditches. 



The old plow-and-scraper method of making ditches is applicable only 

 Avhen the soil is fairly dry. It will not be described here. Except for 

 very small jobs, it is more expensive than excavating with one of the 

 several forms of large ditching machines. 



Of the several types of ditching machines, the floating dredge is the 

 most common and the most successful in level land and for large jobs. It- 

 begins at the upper end of the drainage course and works down stream so 

 that the excavation is always well filled with water and easily floats the 

 dredge. This style of dredge is adapted to a large channel, varying from 

 12 to 60 feet in width. The earth is excavated by large scoops on immense 

 steel arms, operated by steam power. The earth is deposited on either side 

 of the channel and at a distance of 6 to 12 feet from the edge of it. In the 



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