94 ELEMENTS OF AGRICULTURE 



always be kept. This will make it easier to locate any 

 tile that fills up. It will also make it possible to lay ad- 

 ditional tiles in the proper places. 



101. Drainage as a Government Problem. Aside from 

 the problem of drainage on the individual farms, there 

 are many large swamp areas that can be reclaimed by co- 

 operative effort. Professor Shaler estimates that there 

 are over 3,000,000 acres of reclaimable sea-coast marsh 

 land along the Atlantic coast of the United States. The 

 draining of such land is a problem for the United States 

 and state governments, just as is the irrigation of arid 

 regions. It is probable that such lands could be sold for 

 much more than the cost of drainage. The drainage of 

 these areas will not only add to the amount of good farm 

 land, but it will make the coast cities much more healthful. 



SOIL AIR 



102. Importance of Soil Air. Most soils are about 

 half pore space. That is, a cubic foot of dry soil would 

 contain about half a cubic foot of air. As the water in 

 soils increases the amount of air decreases, so that in a 

 saturated soil there is very little air. Soil air is just as 

 essential for the growth of farm crops as air is for animals. 

 If water excludes all air from the soil, the crops will drown 

 just as surely, if not so quickly, as a person drowns in water. 

 There are some marsh plants that can grow in standing 

 water, and rice can do so, but the usual farm crops would 

 utterly fail under such conditions. Even rice requires 

 some air in the soil, as do the submerged seaweeds, but 

 in this case they are able to get air from the water. 



