CONVENTION OF AMERICAN AGRICTTLTURAL C()LLE(4E!^. 829 



SKCTION ON AGRirULTl'RK AND CHEMISTKV. 



Tlie three sessions of thi.s section were occupied chietiy witli papers und discus- 

 sions relating to soils, especially soil fertility. Throughout these discussions there 

 were frequent references to the principles laid down in a recent bulletin of the Bureau 

 of Soils," and their conflict with views which have previously Ijeen held regarding 

 soil fertility and its maintenance. 



The chairman of the section, C. (x. Hopkins, of Illinois, in his opening address on 

 The Present Status of Soil Investigations, pointed out the conflicting conclusions 

 reached by various investigators, particularly with reference to the value of chemical 

 methods of studying the fertility of soils. He illustrated the valuable service that 

 chemical analysis may render in this connection by citing the results of his ow^n 

 studies on various typical Illinois soils, and suggested that discordant views might be 

 harmonized and the work promoted ])y keeping clearly in mind the fact that functions 

 of soils are of two kinds: ( 1 ) to furnish favorable physical conditions for plant growth, 

 and (2) to supply the necessary plant food; i. e., they are both physical and chem- 

 ical, and one is as indispensal)le to the successful growth of crops as the other. The 

 use and value of leguininous crops and fertilizers and manures in rotation for main- 

 taining and increasing soil fertility were illustrated from results of field experiments. 



Milton Whitney, of the Bureau of Soils, in a discussion of Methods for the 

 Extension and Practical Application of Soil Surveys, summarized the work of his 

 Bureau during the past year in surveying and mapping typical soils in different parts 

 of the United States. The main portion of his address, however, was devoted to a 

 discussion of the work of the Bureau on the chemistry of soils as related to crop 

 production, and a preliminary statement w'as made regarding investigations in 

 progress in continuation and extension of those which were made the basis of 

 Bulletin 22 of the Bureau. These include a further study of the physical properties 

 of soils with reference to the movement of the soil water, which has shown little 

 or no difference in the movement of water in widely different soils; studies of the 

 behavior of the soil water as the drought limit is approached, which differs in a 

 marked degree from that of the water of saturated soils or water in mass; experi- 

 ments on the growth of plants in soil extracts, which gave results similar to those 

 obtained in experiments with the original soils, and studies of transpiration as 

 related to the functional activity of plants grown in good and poor soils and in the 

 extracts of the same. 



Transpiration- was less active in the poor soils and their extracts than in good 

 soils, and was influenced by the kind of salts present, but not by the amount. The 

 effect of certain salts in retarding root action and of others in accelerating it was 

 suggested as a possible explanation of the apparent influence of the use of fertilizers. 

 The effect of aeration in correcting the poor results obtained with poor soils or their 

 extracts was noted, and was thought to confirm the position taken in Bulletin 22 

 that the use of fertilizers appears to have the same effect as good cultivation. "It 

 appears now that if we have perfect aeration . . . fertile and poor soils grow plants 

 of equal vigor and feeding capacity." The speaker proi)hesied the development of 

 a method, to be used in the field, in studying the conditions of the soil as related to 

 the growth and functional activity of the plant, and the possible determination of 

 h(jw far these conditions may be changed by aeration or physical treatment. 

 "Certainly I think it is going to be possible for us to determine what fertilizers can 

 be used to correct these difficulties under the conditions of our experiment, which 

 is a long way ahead of anything that we have at the present time." 



A paper by E. W. Hilgard, of California, on The Chemistry of Soils as Related to 

 Crop Production was read in his absence. This paper was an analysis of Bulletin 22 



« U. S. Dept. Agr., Bureau of Soils Bui. 22. 



