104 EXPERIMENT STATION RECOED. 



not underestimated, but the difficulties in studying so complex a 

 question are very great. 



In this connection the presidential address of Dr. E. B. Voorhees, 

 before the American Chemical Society at the Ithaca meeting last 

 summer," is timely and instructive. It deals with Some Problems 

 for Agricultural Chemists, which it shows require the cooperation 

 of other branches of science as well. It makes some specific sugges- 

 tions for lines of investigation which are fundamental in character 

 and are greatly needed at this time to answer the questions of prac- 

 tical men. As indicating the difference between such fundamental 

 investigation and isolated experiments, and as showing something of 

 the method of attack, the address is excellent. 



One of the problems proposed is the ultimate effect of the con- 

 tinued use of commercial fertilizers. It is pointed out that in some 

 cases a condition has resulted from using large quantities of commer- 

 cial fertilizers which makes the soil less responsive or less adapted 

 to certain crops. This effect may be assigned to various causes — 

 chemical, physical, biological, etc. — but in the speaker's opinion we 

 have as yet nothing definite and positive to answer. The question 

 is a very live and important one, and grows in large measure out of 

 the system of fertilization which has been recommended. 



Another problem relates to the decline in productive capacity of 

 soils under cultivation, especially in the richer sections — that is, the 

 loss of fertility. This may be explained in part as due to imperfect 

 chemical or physical or bacteriological conditions of the soil, or of 

 all of these combined, but it is urged that we should not deal in 

 probabilities, and we do not yet know the measure of the effect of 

 these various factors. We must find out what the cause of the appar- 

 ent exhaustion is, be able to show the farmer what his sources of loss 

 are, and suggest a remedy. 



The importance of humus in relation to fertility is another subject 

 mentioned which needs investigation. Notwithstanding all the in- 

 vestigations that have been made, the speaker expressed his conviction 

 that much remains to be learned as to the function of this constituent 

 and the manner of the influence it exerts in maintaining and im- 

 proving fertility of soils. " We are unable from our present knowl- 

 edge to state whether the effect is physical, chemical, or biological, 

 or whether it is a combined effect of each, or whether it is absolutely 

 essential that the organic matter be present in large amounts in order 

 that the best results may be obtained. It is a problem well worthy 

 of the attention of our agricultural chemists, and one which must be 

 solved if we are to give safe advice as to the cultivation of our soils." 



The nitrogen question, the maintenance of the proper supply in 

 the soil and prevention of losses, is also pointed to as one of far- 



o Published in Science, n. ser., 24 (1906), No. 613, pp. 385-390. 



