CONVENTION OF AMERICAN AGRICULTURAL COLLEGES. 329 



Under the first subject Dr. C. ( >. Hopkins presented a paper on Soil 



Fertility in Relation to Permanent Agriculture, in which be called 

 attention to the widespread decline of the fertility of farm Lands in the 

 United States, due to exhaustive systems of cropping and export of 

 fertility from the farm. The extension of animal husbandry, involv- 

 ing the feeding of a large proportion of the crops grown to animals <>n 

 the farm, and thus insuring the return of the fertility to the soil, 

 would act as a partial cheek to this exhaustion; hut it was pointed out 

 that about 80 per cent of the fanners of the United State- are giving 

 attention almost exclusively to crop production, and that a Large pro 

 portion of them will probably never take up animal production t<> an 

 extent that will result in an increase of fertility of their farm- in this 

 way. It is therefore necessary for such farmer- to adopt systems of 

 cropping, supplemented by the use of fertilizers, which will enable 

 them to maintain the balance of fertility or turn it in their favor. 



The experiments of the Illinois Station with various systems of 

 cropping and fertilizing on different soil horizons, on representative 

 Illinois soil areas and types, were briefly reviewed, the results of 

 chemical analysis and pot and field experiments usually agreeing in 

 showing that in these soils phosphoric acid is usually the principal 

 requirement and the only one which needs to be applied in commer 

 rial form. The soils are. as :t rule, abundantly supplied with potash, 

 and nitrogen is readily and cheaply obtained by growing Leguminous 

 plants. The cheapest and most efficient means of supplying the phos- 

 phoric acid has been found to be b} T the use of fine-ground rock phos- 

 phate in connection with green manures or other materials supplying 

 abundance of decaying organic matter. The efficiency of such cheap 

 phosphates a- compared with the more expensive acid phosphates has 

 also been demonstrated at the Maryland. Ohio, and Pennsylvania 

 stations. 



In the discussion following this paper, Director C. E. Thorne 

 pointed out the fact that virgin soils and those long under cultivation 

 behave very differently toward the same systems of cropping and 

 manuring; Dr. II. J. Wheeler called attention to the unsuitability 

 of untreated phosphates to exhausted soils and to market -garden crop-: 

 and Prof. \V. P. Brooks stated that a large proportion of the soils of 

 New England are in special need of potash, and that it i-> impossible to 

 determine the fertilizer requirement of a soil apart from the peculiar 

 needs of the particular crop to be grown, a fact which was strongly 

 emphasized by other speakers. 



In a paper by Dr. A. M. Peter on Some Results of an Old Method 

 for Determining Available Plant Food in Soils, read by the secretary 

 of the section, a compilation was given of the results of determina 

 tions, made in L854 by K. Peter, State geologist of Kentucky, of the 



