586 



SCIENCE 



[N. S. Vol. XXXVI. No. 931 



ism and on the action of fertilizers. These 

 actions of the different fertilizer combina- 

 tions or different fertilizer requirements, 

 as they may be styled, show a certain 

 parallelism with field observations on soils 

 and their fertilizer requirements, and one 

 is tempted to ask to what extent the differ- 

 ent fertilizer requirements of different soils, 

 or of the same soil under different condi- 

 tions, may be influenced by the same cause. 

 That harmful bodies occur in soils has been 

 amply shown and that these are influenced 

 directly or indirectly by fertilizer salts is 

 also clear from these and other researches. 

 That the constitution of the organic matter 

 varies from soil to soil and in the same soil 

 under different conditions of aeration, 

 drainage and cropping is likewise clear. 

 The presence of compounds inimical to 

 plant growth by virtue of a property re- 

 sembling that of any of the above-men- 

 tioned substances might, therefore, cause a 

 different fertilizer requirement, a require- 

 ment which might even change from time 

 to time, according to the nature of the bio- 

 chemical relations producing the body or 

 according to the nature of the plant re- 

 mains in the soil ; in other words, according 

 to the rotation, with its necessarily altered 

 soil management, and the altered biochem- 

 ical changes produced in the different plant 

 remains. 



The soil has vital functions. The soil 

 can not be considered as the dead, inert 

 remains of rocks and previous vegetation, 

 but must be considered as an accumulation 

 of such material in which the process of 

 formation, alteration and transposition are 

 still at work. In other words, the soil in 

 its entirety is not dead or inert, but en- 

 dowed with functions analogous ' to those 

 of life itself. In it take place the same 

 processes of solution and deposition that 

 have taken place in past ages, and are 

 taking place to-day in the geologic proc- 



esses connected with the action of the water 

 on the rocks and minerals of the earth's 

 crust. In it take place the same physical 

 and chemical interactions as take place in 

 the movement of subsurface waters gen- 

 erally, resulting in ore formations or 

 depositions. In it take place the same 

 processes of fermentation, digestion, or 

 decay of organic materials as take place in 

 animals and plants or in the production of 

 industrial products, such as cheeses, wines 

 and beers, brought about in the soil as in 

 these other processes by means of ferments, 

 enzymes, bacteria and fungi or molds. In 

 it take place the same processes of oxida- 

 tion and reduction which play so enormous 

 a part in all life processes, and these re- 

 searches have shown the nature of com- 

 pounds in the soil organic matter to be the 

 same as those derived from such life proc- 

 esses or from similar laboratory processes 

 of digestion, oxidation or reduction. 

 Organic matter is very changeable; it is 

 the material which forms the food, as it 

 were, of all the microorganisms of the soil, 

 of the bacteria, of the molds, of the pro- 

 tozoa, and influences them favorably or un- 

 favorably, just as the higher plants are 

 affected. In turn these agents are great 

 promoters of these changes in the organic 

 debris of soil. All of these processes and 

 the life forms in the soil are affected by 

 fertilizer salts when added to the soil, and 

 changes are produced in the soil, physical, 

 chemical and biochemical, which influence 

 the soil and affect its potential fertility 

 entirely irrespective of the added plant 

 food. In other words, the soil has beeit 

 changed in many prominent characteristics 

 even before any crop is planted therein. 



I must not leave this subject of fertilizer 

 action, in view of the preceding paper, 

 without saying that the Bureau of Soils 

 takes an advanced stand not only on the 

 present use of fertilizers, but on their ex- 



