No. 4.] SOIL FERTILITY. 137 



adopted by the authors in Bulletin No. 22, viz., the treat- 

 ment of a given weight of soil with a given volume of water 

 for a brief period of time, actually test the ca})acity of the 

 soil for sustaining plant growth, even if the soil solution is 

 the sole source of the plant's sustenance? In answering 

 this question I cannot do better than to quote from a recent 

 editorial in the "Country Gentleman:" "It is confessed 

 that the method ' does not tell us what concentration or 

 exact composition of the soil solution in situ has,' and cer- 

 tainly the analytical procedure reveals nothing as to how 

 rapidly or how continuously the soils in question will give 

 up water-solul)le material to meet the needs of a rapidly 

 growing crop. While there may be justification for assert- 

 ing that the weakest solutions obtained by the Bureau of 

 Soils will support plant growth when constantly renewed, 

 nothing whatever is shown as to possibility of such renewal 

 in any given case, and no data are presented which show 

 the effect of the composition of the soil on the rate, perma- 

 nence and character of such renewal. The assumptions of 

 the bulletin are to the effect that in any soil such a renewal 

 will take place with sufficient rapidity to meet the needs of 

 crops under all conditions of growth when the water supply 

 is abundant. Is not this dangerous ground on which to 

 advijcate a reversal of our attitude toward the economics of 

 plant nutrition ? The premises involved in the above absurd 

 syllogism are not supported, and, even if supported, are 

 insufficient, and the reasoning is therefore not convincing." 



The authors of Bulletin No. 22 seemed to be fully aware, 

 as certainly they must be, of the marked results which for 

 many years have followed the use of farm manures and 

 connnercial fertilizers ; but they attempt to explain these 

 results on other grounds than that manures and fertilizers 

 add to the soil certain constituents which previously existed 

 there in insufficient quantities. Their explanation seems to 

 be that the fertilizers modify the physical characteristics of 

 the soil or the chemical nature of the soil solutions, so that 

 the water supply is improved, and the soil becomes a more 

 sympathetic environment for the roots of the growing plant. 

 To this point I shall refer later. 



