660 PROCEEDINGS OF SECTION K. 



The above short review of the work which is being done in the 

 solution of a certain class of soil problems shows that the action of 

 fertilizers is not confined to supplying the crop with food, but that 

 it is far more complex, and that fertilizers influence the physical 

 structure of the soil, and also its biological and chemical condition 

 in a great variety of ways ; further, that v/e have to take into ac- 

 count a large number of factors which influence the fertility 

 of the soil, and which are quite independent of its supply of plant 

 food. 



We have seen that fertilizers may exert an influence on the 

 toxic matters produced in the soil, the texture, and the moisture- 

 condition of the soil, on bacteria and fungi, on the oxidizing 

 power of the soil, and that quite remarkable effects are produced 

 by substances added in quantities much too minute to act as 

 nourishment to the plant. 



I do not for a minute desire to underrate the great importance 

 of manuring in maintaining the fertility of the soil. I only wish 

 to emphasize the point that the old conception of manures as acting 

 solely by supplying plant-food must be abandoned. 



There are, I venture to think, very few who would nowadays 

 recommend a particular manure formula based on the one hand 

 on the composition of the crop, and on the other on the composi- 

 tion of the soil. 



It appears to me that, for the next important advance in our 

 knowledge of fertility conditions, we must look in the near future 

 to the plant physiologists and bacteriologists. 



The great role played by toxic substances, perhaps of bacterial, 

 perhaps of chemical origin, leads us to look for substances which 

 shall restrain their development. 



Just as diseases in men and animals are being combated by the 

 discovery of substances which retard their progress, so it may be 

 hoped that our plant phys"iologists may be able to discover anti- 

 toxins which shall render harmless the poisons which are secreted 

 either by the growing plant or by the metabolism of organic matter 

 in the soil, whether such substances are produced by bacterial agen- 

 cies, or by purely chemical changes. We shall no doubt find that 

 many substances which we now apply in the confident anticipation 

 of increased crop production, act less by virtue of any special plant- 

 food with which they supply the crop than through their power of 

 retarding or preventing the formation of substances hostile to plant 

 growth. 



Soil-analysis will, in the future, concern itself less with the 

 elaboration of methods for determining the proportions of plant- 

 foods than in searching for conditions likely to produce toxic sub- 

 stances and for means to overcome them. 



