REPORT OF THE CHEMIST. 



167 



those of tlio TrifoUum repens plots, was, to the depth examined, suGBoient to accotint 

 for a largo proportion of the nitrogen of the Vicia crops. 



(13) It may he considered estahlished that much, if not the whole, of the nitrogen 

 of crops is derived nitrogen within the soil — accumulated or supplied ; and that muuli, 

 and in some cases the whole, of the nitrogen so derived, is taken up as nitrates. 



(1-1) An examination of a number of the United States and Canadian prairie soils 

 sliowod them to be very much richer in both nitrogen and carbon, to a considerable 

 dt'iith, than the surface soils of old arable lauds in Great Britain, and about as rich, 

 to a much greater depth, as the surface soil of permanent pasture land. 



(15) On exposure of x>ortion8 of some of these rich prairie soils, under suitable con- 

 ditions of temperature and moisture, for specified periods, it was found that their 

 nitrogen was readily susceptible of nitrification, and so of becoming easily avuilablt' 

 to vegetation. 



( IG) After several extractions, the subsoils almost ceased to give up nitric acid; but 

 on seeding them with a tenth of a gram of rich garden soil containing nitrifying or- 

 ganisms, there was a marked increase in the rate of nitrification. This result af- 

 forded confirmation of the view that the nitrogen of subsoils is subject to nitrifica- 

 tion, if uuder suitable conditions, and that the growth of deep-rooted plants may 

 favor nitrification in the lower layers. 



(17) Under favorable conditions of season and of cultivation, the rich prairie soils 

 yield largo crops ; but, under the existing conditions of early settlement, they do not, 

 on the average, yield crops at all commensurate with their richness, when oomiiared 

 with the soils of Great Britain which have been under arable culture for centuries. 

 But so long as the land is cheap, and labor dear, some sacrifice of fertility is unavoid- 

 able in the process of bringing these rich virgin soils under profitable cultivation. 



(18) A comparison of the percentages of nitrogen and carbon in various soils of 

 known history, show that the characteristic of a rich virgin soil, or of a permanent 

 pasture surface soil, was a relatively high percentage of nitrogen and carbon. On 

 the other hand, soils which have long been under arable culture are much poorer in 

 these respects ; while arable soils under conditions of known agricultural exhaus- 

 tion, show a very low percentage of nitrogen and carbon, and a low proportion of car- 

 bon to nitrogen. 



(19) Not only the facts adduced in this and in former papers, but the history of 

 agriculture throughout the world, so far as it is known, clearly shows that, pre-emi- 

 nently, so far as the nitrogen is concerned, a fertile soil is one which has accumulated 

 within it the residue of ages of natural vegetation, aud that it becomes infertile as 

 this residue is exhausted. 



The following table shows the character of exhausted arable soils, 

 of newly laid down pasture lands, and of old pasture soils at Eoth- 

 amsted, England ; of some other old arable soils, of some Illinois and 

 Manitoba i^rairie soils, and lastly, of some very rich Russian soils in re- 

 gard to their percentages of nitrogen and carbon, taken from the same 

 report, p. 419 : 



Table II. — Nitrogen and carbon in various eoils, 



[In dry sifted soil, oalcnlated on soil dried at 100° C] 

 EOTHAMSTBD AEABLE AND GRASS SOILS. 



Date of soil 

 sampling. 



Nitro- 

 gen. 



Carbon. 



Carbon to 

 one nitro- 

 gen. 



Auihoritv. 



Roots, 1843-'52; barley, 1853-'55 ; roots, 1856-'69; 



mineral manures 



Wheat, 1843-'44, and each year since; mineralt 



tuaunres. < 



liiirloy, 1802, and each year since ; mineral man-J 



nres. ( 



Arable laid down to grass : 



Ten acres, Spring, 1879.^ 



Barnfield, spring, 1874 „ ...,. 



Apple-tree field, spring, 1863 



Dr. Gilbert's meadow, spring, 1858 ....... 



Highfleld, spring, (?) 1838 



Very old erass land (the Park) 



Apr., 

 Oct., 

 Oct., 

 Mar., 

 Mar., 



Feb., 

 Feb., 

 Nov., 

 Jan., 

 Sept. 



<Feb. 



^Mar., 



1870 

 1865 

 1881 

 1868 

 1882 



1882 

 1882 

 1881 

 1879 

 ,1878 

 and) 

 18765 



Per ct. 



.0984 

 .1119 

 .1012 

 .1202 

 .1124 



.1235 

 .1509 

 .1740 

 . 2057 

 .1943 



.2466 



Per ct. 



1.039 

 1.079 



1.154 



2.412 



2.403 



8.377 



Per cent. 



9.3 



10.7 



10,3 



11.7 

 12.4 



13.7 



EothamsteiL 

 Do. 

 Do. 

 Do. 

 Do. 



Do. 

 Do. 

 Do. 

 Do. 

 Do. 



Do. 



