EXPERIMENT STATION RECORD. 



Vol. XXIII. Abstract Number. No. 4. 



RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICTJLTUEAL CHEMISTRY— AGROTECHNY. 



Contributions to soil analysis, J. H. Pettit {Jour. Landw., 51 (1909), No. 

 S, pp. 237-267, fig. 1; ahs. in Jour. Clieiii. Soc. [London], 98 {1910). No. 567, II, 

 p. 65; Analyst, 35 {1910), No. 409, p. 177). — These experiments were conducted 

 for the purpose of obtaining knowledge as to the plant nutrients extracted by 

 dilute solvents and the relation of these nutrients to the fertility of the soil. 

 Particular effort was made to establish a relationship between the results 

 obtained by the methods of von Sigmond (E. S. R., 19, p. G) and Schloesing 

 (E. S. R.. 15, p. 344). 



From the results obtained with the 6 soils examined it is evident that there 

 is a definite natural limitation of the solubility of soil phosphates. If the 

 basicity of the soil is considered, the uniform active concentrations of the 

 nitric acid lie within certain definite limits, namely, about 400 to SOO mg. N^O^ 

 per liter of the acid soil extract solution. The potassium oxid of the 6 soils 

 with the method employed showed some differences in regard to solubility, some 

 being slightly soluble and others readily soluble. Only in the case of the loam 

 was a uniform effective concentration found. The relation existing between the 

 soil and the total phosphoric acid or the potassium oxid content (soluble in 

 hydrochloric acid of specific gravity 1.15) is not the same as that which is 

 present when these are dissolved out with nitric acid. Shell marl, for instance, 

 although it contains more total phosphoric acid than new red sandstone (bunt- 

 sandstein), has only one-third as much easily soluble phosphoric acid as the 

 latter. Loam contains two and one-half times the quantity of potassium oxid 

 which the new red sandstone contains, but its content of easily soluble potas- 

 sium oxid is only about three-fourths of that of the latter. 



The results of pot experiments with buckwheat, barley, potatoes, and loamy 

 and shell marl soils corresponded closely with those obtained from chemical 

 analysis. The amount of ])otassium oxid and phosphoric acid which was taken 

 up by these plants, with one exception, was not the same as that soluble in 

 dilute nitric acid. Further, there was no general relationship between the 

 phosphoric acid and potassium oxid absorbed by one plant from the 4 soil 

 pots and the readily soluble phosphoric acid and potassium oxid which was 

 originally present in the soils. The various plants exhibited much difference 

 in their capacity for taking up nourishment from the soil. Buckwheat, for 

 instance, absorbed from a loamy soil three and one-half times as much potas- 

 sium oxid and twice as much phosphoric acid as barley, which makes it obvious 



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