vi SOIL CONDITIONS AND PLANT GRO WTH 



book, with the results that the book is much improved, 

 and a definite continuity is assured between this general 

 monograph and the detailed monographs to which it 

 will serve as a link. The whole series is to be called 

 "The Rothamsted Monographs on Agricultural Science". 



It is hoped that this new arrangement will prove 

 satisfactory to students. It has the advantage that the 

 book still covers the whole ground, while remaining of 

 a manageable size, and that it is closely linked up with 

 a series of similar books, each dealing with separate 

 sections, in which more complete treatment and more 

 fully informed criticism are given than I could myself 

 undertake. 



On the other hand, the necessity for freedom of 

 treatment, and the difficulty of placing such subjects as 

 >Soil Physics or Soil Protozoa under the heading of 

 Biochemistry, compelled the withdrawal of the book 

 from the important " Biochemical Series," of which it has 

 hitherto been a member. And, although Drs. Plimmer 

 and Hopkins willingly consented, this course was not 

 taken without serious consideration and regret : it in- 

 volves the separation of the book from a very useful 

 series of volumes. 



Perhaps the most striking feature of the past ten 

 years' developments has been the increasing recognition 

 of the complexity of soil phenomena. The American 

 investigations have shown how complex are the physico- 

 chemical relations of the soil, the soil solution and the 

 plant. English work has shown that the soil population 

 is numerous and very varied. It is not sufficiently 

 recognised, however, that this complexity necessitates a 

 difference in method of investigation from that usually 

 adopted in scientific laboratories, and this I have tried 

 to bring out in the course of the book. A chemist 



