124 EXPEKIMEXT STATION EECOKD. 



tnking up of food from the soil by plants is thought to be effected by an ex- 

 change of ions. 



The employment of dialysis and the determination of the power of oxi- 

 dation as a convenient method for the judgment of soils, J. Konig (Fest- 

 schrift 84- Versamml. Deut. Xaturf. u. Arzte von der Med. Naturw. Gesell. 

 Minister, 1912, pp. 57-77, ph 1, fig. 1). — See also the article noted above. 



The soil solution, and the mineral constituents of the soil, A. D. Hall, 

 Winifred E. Beenchley, and Lilian M. Underwood {Phil. Trans. Roy. Soc. 

 London, Ser. B, 204 (1913), No. 307, pp. 179-200, figs, g).— Wheat and barley 

 were grown in solutions made from soils on which wheat and barley had been 

 grown for 60 years. The growth in the solutions was parallel to that on the plats 

 and the composition of the solutions as regards phosphoric acid and potash 

 corresponded to the past manurial treatment and present analysis of the plats. 

 Growth in the solutions from imperfectly manured plats was brought to the 

 level of that in solutions of completely manured plats by the addition of suitable 

 salts. "Wheat ^ew as well as barley in the solutions of the wheat soils and 

 vice versa. In a similar set of solutions from the same soil the growth of buck- 

 wheat, white lupines, and sunflowers corresponded with that of wheat and bar- 

 ley. Boiling effected no alteration in the nutritive value of the soil solutions." 



" In nutritive solutions of various degrees of dilution the growth of plants 

 varied directly, but not proportionally with the concentration of the solution, 

 though the total plant food present in the solution was in excess of the require- 

 ments of the plant. When the nutrient solution was diffused as a film over 

 sand or soil particles, as in nature, there was no retardation of growth due to 

 the slowness of the diffusion of the nutrients to the points in the liquid film 

 which had been exhausted by contact with the roots. Growth in such nutrient 

 solutions forming a film over sand particles was much superior to the growth 

 in a water culture of equal concentration, but the growth in the water culture 

 was similarly increased if a continuous current of air was kept passing 

 through it." 



" From the results obtained it is generally concluded : (1) The composition of 

 the natural soil solution as regards phosphoric acid and potash is not constant, 

 but varies significantly in accord with the composition of the soil and its past 

 manurial history. 



"(2) Within wide limits the rate of growth of a plant A^aries with the con- 

 centration of the nutritive solution, irrespective of the total amount of plant 

 food available. 



"(3) When other conditions, such as the supply of nitrogen, water, and air 

 are equal, the growth of the crop will be determined by the concentration of the 

 soil solution in phosphoric acid and potash which, in its turn, is determined by 

 the amount of these substances in the soil, their state of combination, and the 

 fertilizer supplied. 



"(4) On normal cultivated soils the growth of crops like wheat and barley, 

 even when repeated for 60 years in succession, does not leave behind in the 

 soil specific toxic substances which have an injurious effect upon the growth 

 of the same or other plants in that soil." 



The net result of these investigations is thought to uphold the theory of the 

 direct nutrition of the plant by fertilizers. 



Results of ten years' comparative field experiments on the action of fal- 

 low, manure, and clover, A. Koch (In Festschrift zum sieb.^igsten Gehurtstage 

 von Jacob Esser. Berlin, 1913, pp. 57-93, figs. 3; Jour. Landw., 61 (1913), 

 No. 3, pp. 245-281, figs. 3). — ^Three systems of soil treatment were followed in 

 the experiments reported in this article. These compared unfertilized black 

 fallow, manure (on potatoes or beets), and clover in a rotation of three cereals 



\ 



