RELATION OF FERTILISERS TO SOIL FERTILITY. 19 



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 emphasise 

 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 composition 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 the bacteriologists. 



The great r6le played by toxic substances, perhaps of bacterial, perhaps of 

 chemical origin, leads us to look for substances which shall restrain their 

 development for antitoxins. 



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 

 physiologists may be able to discover antitoxins which shall render harmless 

 the poisons which are secreted either by tke growing plant or by the 

 metabolism of organic matter in the soil, whether such substances are 

 produced by bacterial agencies or bypurely 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 substances, and for means to overcome 

 them. Unfertile conditions, whether due to soil-bacteria, fungi, or the 

 formation of poisonous chemical substances, will be combated by the same 

 weapons as are now employed against similar diseases in men and animals. 



Whilst there is no intention in all that has gone before to suggest for a 

 moment that we should cease to manure with the recognised fertilisers 

 potash, nitrogen, and phosphates or that we should cease to conduct 

 experiments as to the best proportions of these manures for different crops, 

 still I feel that future progress in this matter lies more with actual farmers' 

 experiments, where the principles already established by careful scientific 

 investigations can be tested and modified to suit local conditions. I feel 

 that the time occupied in elaborate manure experiments on the old lines, and 

 in the elaboration of methods of soil analysis on the old lines, would be 

 better spent in the study of other factors productive of soil fertility or 

 infertility such as some that I have outlined above and I hope that it may 

 be possible for some of our Australian workers to devote more time to plant 

 hpysiology, to the study of soil toxins, and the elucidation of the conditions 

 which render a soil fertile or infertile whether these are physical, chemical, 

 or biological in their nature. 



