SOIL WATER 119 



Removing Excess of Water. Excess of soil water pertains only to 

 that above described as gravitational water. This may be removed by 

 deep, open drains and by underdrains. Methods of drainage will be dis- 

 cussed in another topic. 



On comparatively levei lands where surface water often accumulates, 

 its escape may be encouraged by so plowing the land that it will lie in slight 

 ridges and continuous depressions. If the depressions have a continuous 

 fall, all of the surface water will slowly escape from the land into natural 

 drainage channels and without causing erosion. 



Excess of water is sometimes removed by the use of crops, although 

 this does not pertain to gravitational water. In most localities it is desir- 

 able to have the growth of orchard trees cease as the season draws to a 

 close, in order that the wood may harden and withstand winter freezing. 

 For this purpose orchards are frequently planted with crops that draw 

 heavily on the soil moisture for the purpose of so exhausting it that the 

 growth of the trees will be checked. This serves not only a good purpose 

 with reference to the condition of the orchard, but produces organic 

 matter that may be plowed under for the benefit of the soil and the trees. 



LAND DRAINAGE 



A wet soil is cold and late. It can seldom be plowed and tilled at 

 the proper time. Most farm crops do not make satisfactory growth in a 

 wet soil, and, therefore, it seldom pays to farm such land. 



Wet lands, when drained, are generally above the average in fertility. 

 Money invested in drainage seldom fails to bring good returns. In many 

 cases the increase in crops, following drainage, has paid for its cost in 

 one year. 



Drainage Increases Warmth and Fertility of Soil. When an excess 

 of soil water is removed through underground drains it permits the soil 

 to warm up rapidly under the influence of the sun; lengthens the growing 

 season; increases the number of days during which the soil is in good 

 condition to plow; increases aeration of the soil; encourages the deep 

 penetration of the roots of plants, and as a result makes the plants 

 resistant to drought. Drainage is, therefore, the first essential to soil 

 fertility. 



Improves Health Conditions. Drainage also improves health con- 

 ditions. The drainage of large areas of swampy land in the vicinity of 

 populous districts has often been undertaken for this purpose alone and 

 without any regard to the increased agricultural value of the land. Large 

 portions of the prairie region when first settled were sufficiently wet to 

 furnish abundant breeding places for mosquitoes. The great numbers of 

 mosquitoes were not only a great annoyance, but were responsible for 

 thousands of cases of malaria, which greatly reduced the health and 

 efficiency of people living in that region. Tile drainage that has been so 

 extensively established in most of that region has practically abolished 



