EFFICIENCY OF FERTILIZERS 359 



tile drainage does much to increase crop production, 

 and to effect economy in the use of fertilizers. The rela- 

 tion of soil drainage to soil fertility may be summarized 

 as follows. (See, also, page 239.) 



(1) Aeration provided by the removal of water 

 greatly facilitates nitrification. This relieves the con- 

 stant necessity for the use of soluble nitrogen fertilizers, 

 and makes it possible to rely largely upon the use of 

 leguminous crops for nitrogen fertilization. Aeration 

 also renders the other fertilizing constituents of the soil 

 more easily soluble. 



(2) By quickly removing the excess moisture in the 

 early spring, and thus increasing the length of the grow- 

 ing period, plants secure more nutriment, there is a cor- 

 responding increase in the length of time in which nitri- 

 fication can take place, also in other action brought 

 about by aeration. Available nitrogen thus produced 

 at an early period in the crop growth is more effective 

 than a later supply would be. 



(3) By removing an excess of water from the soil, a 

 larger proportion of the available fertility, both natural 

 and that added in manures, is absorbed by the crop. 

 This is because the solution is less dilute, and conse- 

 quently a larger amount of mineral nutrients pass 

 through the plant by transpiration. 



229. Soil acidity. An acid condition of the soil 

 renders ineffective a large proportion of the fertilizing 

 material that might otherwise be available. A good 

 illustration of this is the comparison of the crops grown 

 on acid soil when treated with lime with a similar soil 

 not so treated. The size of the crop on contiguous plats 



