338 SOILS. 



deficiency manifests itself in the form or development of the 

 plant, so clearly as to render chemical analysis unnecessary 

 (see below, chapter 22). 



To a certain extent the latter idea has been and is constantly 

 being utilized in practice. It is essentially involved in the 

 habit of judging of land by its natural vegetation ; and by agri- 

 cultural chemists and intelligent farmers, when they check ex- 

 cessive growth of stems and leaf (indicating excess of nitro- 

 gen) by the use of lime or phosphates; or prescribe the use of 

 nitrogenous manures when a superabundance of small, un- 

 marketable fruit is produced. From the coincidence of such 

 indications with the results of the analyses of soils and ashes, 

 very definite and permanently valuable indications as to the 

 proper fertilization and other treatment of the land may be 

 deduced. 



Godlewski insists strongly, and with a good deal of plausibility, upon 

 the importance of making such trials in the open field and not merely 

 in pots. While this is true, it is also true that such field experiments 

 suffer from the same liability to imperfection as the " plot fertilizer- 

 test " plan just described ; viz., that the season may exert a much more 

 powerful influence than the fertilization, and the tests may lead to 

 wholly erroneous conclusions unless the experiments are continued for 

 a number of years, and under skilled supervision. But when once the 

 normal ratio between the ash ingredients for a particular soil and 

 climatic region have been ascertained, the data will be of lasting benefit 

 to agriculture there, and perhaps, other things being equal, to the world 

 at large. 



H. Vanderyst has discussed the entire subject of physio- 

 logical soil analysis elaborately in the Revue Generate Agro- 

 nomique of Louvain, 1902-3 (Exp't St. Record, April 1904, 

 Vol. 8, page 757) and shows in detail the conditions under 

 which it may be successful. Among these he reckons as full a 

 knowledge of the chemical characteristics of a soil as can be 

 obtained by chemical analysis. 



Chemical Tests of Immediately Available Plant-food. It is 

 scarcely doubtful that plants differ considerably in the energy 

 of their action upon the " reserve " soil ingredients; hence no 

 one solvent used by the analyst could represent correctly the 



