ORGANIC MATTER AND NITROGEN 195 



It is the decay of organic matter, and not the mere presence of it, 

 that gives " life " to the soil. Partially decayed peat produces no 

 such effect upon the productive power of the soil as follows the 

 use of farm manure or clover residues. 



DECAY OF ORGANIC MATTER 



A matter that has led to much confusion and misunderstanding 

 is the common talk of " available plant food," as distinct from the 

 total supply, whereas there is no line of distinction. The question 

 as to the amount of available plant food contained in the soil at 

 any given time is very insignificant in comparison with the ques- 

 tion how to make plant food available. The plant food removed 

 from the soil by a crop is not available when the crop is planted, 

 but it must be made available during the growing season. 



Plant food is made available by chemical and biochemical 

 processes, of which ammonification and nitrification are among 

 those best understood. 



For the exact information we now have regarding these processes, 

 we are indebted to the researches of Pasteur and Schlosing and 

 Miintz of France, Winogradsky of Russia, Warington of England, 

 and others. The nitrogen in the soil is almost entirely in organic 

 compounds; that is, the nitrogen is united or combined with 

 other elements, notably carbon, hydrogen, and oxygen, with 

 small amounts of phosphorus, and sulfur, in the form of partially 

 decayed organic matter; but plants cannot use these insoluble 

 organic compounds of nitrogen occurring in the soil. 



There are at least three different kinds of microscopic organisms 

 (called bacteria), and also three different steps, or stages, involved 

 in the process of nitrification, the nitrogen being changed from the 

 organic compounds, first into the ammonia 1 form (NH 3 ), second 

 into the nitrite form, as Ca(NO 2 ) 2 , and third, into the nitrate 

 form, as Ca(NO 3 ) 2 . During the process the nitrogen is separated 

 from the carbon and other elements composing the insoluble or- 

 ganic matter, and is united or combined with oxygen and some alka- 

 line element to form the soluble nitrate, such as calcium nitrate, 



1 Technically this first step (ammonification) is preliminary to, and not a part 

 of, nitrification proper. 



