170 BOARD OF AGRICULTUKE. [Pub. Doc. 



Importance of Soil Physics. 



This chemical explanation of soil fertility is very gener- 

 ally accepted by practical farmers and by fertilizer manu- 

 facturers. Stockbridge, Johnson and others, by writings, 

 lectures and field work, were spreading the results of inves- 

 tigations along this line almost a generation ago. But even 

 then they saw the difficulties in the way of a complete ex- 

 planation of soil fertilit}^ by chemistry alone. While chem- 

 istrj^ is still the most important component of agricultural 

 science, and without the explanations it brings agricultural 

 knowledge would be unclassified, if not chaotic, the newer 

 findings of soil physics and soil bacteriology are needed to 

 supplement practice in conserving and increasing soil fer- 

 tility. The facts that are being brought out by these new 

 sciences cannot as yet be said to have replaced, and perhaps 

 are not likely to replace, the old chemical outlook, but they 

 are supplementing where they do not supplant. Soil science 

 is at present in a more or less transitor}' stage. While it is 

 not possible to affirm with the positiveness of twenty-five 

 years ago with regard to the fundamentals of soil science 

 and practice, there are some things that have been learned ; 

 and if our practice is to keep pace with new knowledge, we 

 must 1)6 alive to all that these new classes of facts mean. 



The Soil not a Dead Thing. 



The profoundest change that has come about — and it has 

 come so gradually that we have not all really recognized 

 it — is the fact that soil, instead of being a dead, inert thing, 

 holding dead plant food to be assimilated and made alive by 

 growing plants, is teeming with life. It is now recognized 

 that the soil is not a chemical laboratory, and that it is not 

 merely made up of a number of independent chemical sub- 

 stances in various stages of hardness and solul)ility. In- 

 stead of being an inert physical mass, the soil is in reality 

 full of germ life. While the knowledge of soil bacteria has 

 not advanced to the point that ])ositive deductions can be 

 drawn in other than a limited and })erha])s tentative way, 

 still, the results are so important in their bearing upon the 



