CHAPTER XI 



NITRIFICATION AND THE COMPOSITION OF DRAINAGE WATERS 



I. The Process of Nitrification. 

 II. Denitrification. 



III. Nitrates in Cultivated Soils. 



IV. Nitrates in Manured and Cropped Soils. 

 V. The Nitrates in Drainage Waters. 



VI. Other Constituents of Drainage Waters. 

 References. 



I. THE PROCESS OF NITRIFICATION. 



THE fact that cultivated soils could induce the conversion 

 of organic matter containing nitrogen into nitrates has been 

 known for a long time, indeed it was for many years utilised on 

 a commercial scale for the production of nitre. Many of the 

 conditions under which nitrification takes place had been 

 worked out by the men in charge of the old saltpetre beds 

 before Boussingault and other investigators considered them 

 afresh from the point of view of agriculture. The presence 

 of calcium carbonate or some other base, the aeration of the 

 soil, warmth, and a certain proportion of water had been 

 shown to be necessary, while it was known that much organic 

 matter was injurious. That the action is brought about by 

 a living organism, was first established by the experiments 

 of Schloesing and Miintz in 1877 ; and on the appearance 

 of their paper, Warington, who was then working in the 

 Rothamsted laboratory on the subject, of nitrates in the soil, 

 proceeded to a further investigation of this important subject. 

 His first experiments confirmed the conclusions reached by 

 Schloesing and Mtintz, and showed that the amount of nitrates 



