August 30. 1907] 



SCIENCE 



271 



depletion of soil nitrogen under certain 

 conditions of farming, on the one hand, 

 and, on the other, the extent to which 

 nitrogen enrichment may take place when 

 nitrogenous organic matter is allowed to 

 decay in the soil. 



To procure figures that would illustrate 

 the injurious effect on soils by continued 

 grain growing interspersed with fallowing, 

 we obtained from our Experimental Farm 

 at Indian Head, Sask., in 1905, a sample 

 collected from an area that had been broken 

 in 1882 and that had between that date 

 and 1905 borne six crops of wheat, four of 

 barley, and three of oats, with a fallow 

 between each crop since 1887, nine fallows 

 in all. No manure or fertilizer had ever 

 been applied. 



DEPLETION OF SOIL NITKOGElSr 



Nitrogen Content of Virgin and Cultivated Soils, 

 Indian Head, Sask. 



HISTOEY or CULTIVATED 



1883, wheat, 



1884, wheat. 



1885, wheat. 



1886, barley. 



1887, wheat. 



1888, fallow. 



1889, oats. 



1890, fallow. 



1891, barley. 



1892, fallow. 



1893, wheat. 



1894, fallow. 



1895, oats. 



1896, fallow. 



1897, barley. 



SOIL 



1898, fallow. 



1899, wheat. 



1900, fallow. 



1901, oats. 



1902, fallow. 



1903, barley. 



1904, fallow. 



For comparison, a sample of soil was 

 taken from an adjacent area that had 

 never been cultivated, the point of col- 

 lection being about 120 feet away from 

 where the cultivated soil samples were 

 taken. Each sample was, of course, of a 

 composite nature. There is every reason 

 to believe that the soil over the whole area 

 was originally of an extremely uniform 

 nature and with a similar nitrogen content 

 throughout. 



Samples were taken representative of the 

 first four and eight inches, respectively, 

 and the nitrogen results, calculated to the 

 water- free soil, are as follows: 



In this comparison I am obliged to 

 assume that the virgin soil is no richer 

 to-day in nitrogen than it was twenty-two 



years ago. This is not, .of course, strictly 

 correct, for we must suppose that this 

 prairie soil with its annual crop of grass 

 would year by year increase its nitrogen 

 content. The increase, however, we think, 

 could not be such as to materially affect 

 the significance of the above figures. 



The loss of nitrogen consequent upon 

 this style of farming is seen to be enor- 

 mous. It presents an aspect of western 

 farming of a most serious character. Yet 

 there has not been, so far as we can judge, 

 any marked diminution in the yield dur- 

 ing this period; provided climatic condi- 

 tions are favorable, it is held that this 

 cultivated soil will give as fine a crop as 

 it did twenty years ago. The reason is 

 that there is in this soil to-day in spite of 

 its losses a nitrogen content about twice 

 that considered necessary to the produc- 

 tion of a maximum crop— it was one of 

 the richest soils; it still is one of excep- 

 tional fertility. In such a matter as this 

 chemistry is as a watchman upon the tower 

 warning us of trouble that is yet afar off 

 and which we still have time to avert; 

 interrogating the soil by pot culture, so 

 much favored by some, would be of no 

 value in announcing the fact that most 

 disastrous losses are taking place. 



The next enquiry in this soil study is, 

 what proportion of this loss may be due 

 to removal by crops, what proportion to 

 cultural operations? To answer this we 



