272 



SCIENCE 



[N. S. Vol. XXVI. No. 661 



have calculated the nitrogen contained in 

 the various grain crops produced, and find 

 that from this cause there has been re- 

 moved during this period, approximately, 

 694 pounds per acre. If we subtract this 

 amount from the total loss, calculated to 

 a depth of eight inches of soil, we shall 

 see that more than twice as much nitro- 

 gen has been dissipated by our methods 

 of cultivation than is removed in the crops. 

 The loss ordinarily in the grain growing 

 districts of the west would not in all prob- 

 ability be as great as that here recorded, 

 because as a rule the land is fallowed every 

 third year only, and not every other year, 

 as with the soil under discussion. Never- 

 theless, the deterioration must be marked 

 and I fear unless checked the experience 

 of the extreme east may be at no very 

 distant date that of the west. It seems 

 to me incumbent upon us at once to seek 

 for methods that are less wasteful— we 

 must introduce a crop for the west as we 

 already have for the east, occasionally, or 

 better still systematically, as in a rotation, 

 that will keep up the store of organic 

 matter and nitrogen. 



The natural means for replenishing the 

 soil with these organic constitutents is of 

 course farm manures, but unfortunately in 

 the districts where such are most required 

 the supply is frequently inadequate. We, 

 therefore, at once fall back upon the 

 leguminosEC— the nitrogen gatherers. These 

 are na:ture's soil enrichers. We know of 

 no other family of plants that can be used 

 on the farm possessing the unique and 

 valuable property of appropriating the 

 free nitrogen of the air— nitrogen which 

 may be subsequently made available for 

 succeeding crops. Not that the fertilizing 

 value of the legumes lies simply and solely 

 in the nitrogen they contain, though therein 

 is their chief merit ; the large quantity of 

 humus-forming material they furnish, the 



mineral matter — potash, phosphoric acid, 

 and lime— set free in their decomposition, 

 are features the significance of which, 

 I think, has been somewhat over- 

 looked. It is, however, simply from the 

 standpoint of nitrogen that I shall present 

 certain data at the present time. They 

 will serve to illustrate the three methods 

 we have employed to demonstrate the 

 manurial value of clover and other 

 legumes, viz. : by analysis of the legumes, 

 by estimation of the nitrogen in the soil 

 before sowing the legume and after its 

 decomposition, and by determining the 

 yields of various farm crops following this 

 use of the legumes. 



NITROGEN CONTENT OF VARIOUS LEGUMES 



There are presented in the following 

 table data showing the weight of crop and 

 nitrogen per acre furnished by eight of 

 the more common legumes, the deter- 

 minations being made on the foliage (stems 

 and leaves) and roots (collected to a depth 

 of nine inches), respectively. 



Of course, no attempt will be made to 

 say what proportion of this nitrogen was 

 obtained through the agency of the nitro- 

 gen-fixing bacteria, but of the strong proba- 

 bility that the greater part was from the 

 atmosphere we have, I think, good evidence 

 in the fact that all these legumes were well 

 provided with nodules on their roots, and 

 also that there is, all things considered, a 

 remarkable agreement between these figures 

 and the increase in soil nitrogen due to the 

 decomposition of the legume crop. 



Further, I wish you to consider these 

 results as merely indicative— the amount of 

 nitrogen appropriated and available for 

 manurial purpose would undoubtedly be in- 

 fluenced, within certain limits, by the char- 

 acter of the soil, the prevalence of the nitro- 

 gen-fixing bacteria and the nature of the 

 season. In this matter I have been in the 



