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ELEMENTS OF AGRICULTURE 



CHAPTER XX.— How Soils Lose Nitrogen 



103. Nitrogen Necessary to Fertile Soils. — Many 

 cultivated soils become worn and unfit to produce 

 profitable crops through the loss of their supply of 

 organic matter which contains nearly all the nitrogen. 

 A supply of nitrogen is just as necessary for growing 

 crops as a supply of water; and the nitrogen supply of 

 soils is to a certain extent dependent upon the water 

 supply, because the bacteria which change the protein 

 into soluble compounds of nitrogen cannot work in 

 perfectly dry soils. In order, then, that soils may con- 

 tain nitrogen, they must contain a supply of moisture. 

 As cultivated lands are robbed of their water supply, 

 becoming hard and dry, they are at the same time 

 being robbed of their nitrogen. A dry soil can supply 

 the plant with neither water nor nitrogen, and is said 

 to be deficient in these two plant foods. 



104. Decay of Organic Matter Necessary to Form 

 Nitrogen. — To contain a supply of nitrogen soils must, 

 in the first place, contain some form of decaying vege- 

 table or animal matter; and, in the second place, in 

 order that the organic matter may decay and other 

 compounds of nitrogen be formed, the conditions in 

 the soil must be favorable to the bacteria which cause 

 the changes. ' 



105. Loss of Nitrogen Through Cultivation.— On 

 wooded lands the leaves of the trees die, fall to the 

 ground and go to form humus in the soil; the trees 



