346 



ANNUAL REPORT OF THE 



Off. Doc. 



Table V. 



Source of Soil. 



o. 



M 



1> 



*0 OQ 



Rothamsted soil, first 9 Inches 



Do. with ammonium chloride added, 



Manitoba soils, Lawes and Gilbert 



Soil. Deh6rain, 



0.5S8 

 0.944 

 0.700 

 0.76-1.09 



119 



119 



235 



90 



Tlie large quantities of nitrates produced in the rich Manitoba 

 soils is due to the relatively large amounts of humus which they 

 contain; the figures for the Rothamsted soil in the same table will, 

 therefore, represent a more normal and average condition. 



More detailed figures regarding rates of nitrification are given in 

 Table VI^^ for one of the poorest of the Manitoba soils. 



Table VI. 



Depths — Inches. 



Nltrog-en as Nitric Acid Produced per Day 

 During Different Periods of Exposure, 

 in Pounds, Per Acre. 



Periods of Exposure. 



O — 'O 



11 "ON 

 bD 11 



rv a d 



1-12. 

 13-24, 

 25-36, 

 J7-48, 



0.69 

 0.27 

 0.03 

 0.02 



4.78 

 1.64 

 2.07 

 1.23 



The preceding table shows: 



1. That the greater proportion of the nitrates, nearly 65 per cent., 

 are produced in samples from the first 12 inches of soil; both be- 

 cause of the greater quantity of humus in the surface layer and per- 

 haps also because of the greater vigor of the nitrifying ferments in 

 this same zone. 



2. That in zones between 12 and 36 inches below the surface large 

 quantities of nitrates can be found, 30 per cent, of the whole, pro- 



