CHAPTER XIV 



DRAINAGE 



GENERAL CONSIDERATIONS 



The presence of superfluous water is as detrimental to 

 agricultural land as an inadequate supply, but it generally 

 does not require so great an expenditure of labor and money 

 to remedy the former condition. The method of disposing 

 of the water will depend to some extent upon its source. 

 Early drainage systems are of historic interest only, and this 

 chapter will deal with present-day practices. 



Benefits of drainage. Drainage increases the productivity 

 of wet lands and reduces the labor necessary for cultivation. 

 It permits of freer circulation of air into the soil, which 

 results in the deeper penetration of frost in winter and earlier 

 warming of the ground in the spring, both of which are of 

 benefit to agriculture. Roots extend deeper into a dry soil, 

 and for this reason drouths are not so disastrous. Soils that 

 contain no free water are not affected by winter heaving or 

 summer cracking, and as a result plant roots are not torn 

 apart in the winter nor injured by the dry hot air which 

 enters cracks in the earth in a dry season. Erosion of the 

 fertile surface soil is prevented, and the light vegetable 

 matter and fertilizing materials on the surface of the crop- 

 producing fields are left distributed where needed and not 

 floated away at every rain. 



All health authorities recognize that sanitary conditions 

 are improved by the removal of surplus water, and no other 

 measure is so effective in destroying the breeding places of 

 mosquitoes, greenhead flies, and other annoying insects that 

 require wet ground and small ponds for their reproduction. 

 All road experts agree that thorough drainage practically 



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