134 SCIENCE PROGRESS 



have been carefully carried out have already afforded proof that 

 valuable results are to be obtained in this direction. 1 



In the present article, however, it is proposed to consider 

 purely scientific soil investigations and it must be admitted that, 

 on the whole, in England, up to the present, the amount of work 

 done on pasture soils and the special problems these afford are 

 not very considerable. All the important contributions to our 

 general knowledge of the factors governing soil fertility have 

 been the result of the study of arable soils, which so far have 

 almost monopolised attention. It is natural that arable soils 

 should have been first studied in detail ; but we have to recognise, 

 in applying the results to the case of soils which are permanently 

 occupied by grass, that a number of new conditions are intro- 

 duced which exert an influence in various directions on the 

 processes going forward in the soil and considerably modify the 

 nature of the problems with which we have to deal. It is most 

 important to know to what extent conclusions based on the 

 study of arable soils are directly applicable to the conditions 

 obtaining in pasture soils and whether the same methods of 

 investigation can be made use of in both cases. 



In dealing with grass land, we have primarily to take 

 account of the fact that the soil is occupied by the crop con- 

 tinuously. What then is the effect of the long-continued action 

 of one character of growth upon the soil ? What differences 

 <4oes the continuous presence of a crop make to a soil from the 

 biological, chemical and physical points of view ? There is 

 extremely little detailed knowledge available upon these points 

 and we can still scarcely do more than point out a few of the 

 possibilities and suggest some of the lines along which inves- 

 tigation is still needed. 



In the first place, the continuous action of the roots of the 

 same species of plants, always absorbing food and water, always 

 respiring and excreting, by its effect upon the atmosphere within 

 the soil and upon the soil itself, must certainly exert a direct 

 influence upon the nature of the living organisms — and especi- 

 ally of the bacterial flora. In what direction this influence acts 

 can be at present a matter of speculation only : it is possible 

 that it tends to make a more fixed and unvarying flora, one that 



1 See especially the account of experiments on " The Influence on the Pro- 

 duction of Mutton of Manures applied to Pasture," by Somerville (Supplement 

 to the Journal of the Board of Agriculture, vol. xvii. No. 10). 



