COMMERCIAL FERTILIZER MATERIALS 469 



sulfur from the soil than is indicated by the earlier analyses 

 of plant ash, since considerable sulfur was lost by volatization 

 in the former determination. On the basis of their own 

 methods, they present the data given as to the removal of 

 sulfur trioxide and phosphoric acid from the soil by average 

 crops. (See Table XCVII, page 468.) 



It is to be noted that the amount of sulfur removed by crops 

 is generally about equal to and in some cases much in excess 

 of the phosphoric acid taken from the soil. The fact that 

 soils are generally as low in sulfur as in phosphoric acid lends 

 weight to the argument, that if the latter is a limiting factor 

 in productivity the former should be also. 



To ascertain whether the supply of sulfur in the soil is 

 really depleted by cropping, Hart and Peterson made parallel 

 determinations of sulfur in five virgin soils and in five soils of 

 the same respective types that had been cropped for sixty 

 years. In each type the cropped soil contained less sulfur 

 than the virgin soil, the average for the former being .053 

 per cent. SO3 and for the latter .085 per cent. SO3. 



Considerable sulfur is added to the soil every year in the 

 rain-water, largely in the sulfate form, although near cities 

 appreciable amounts of hydrogen sulfide and sulfur di-oxide 

 are formed. The amount of such sulfur is variable. Miller,^ 

 at the Rothamsted Experiment Station, reports 17.4 pounds 

 of SO3 to the acre, while Crowther and Ruston ^ near Leeds, 

 England, found 161 pounds of SO3 to the acre. Peck ^ found 

 the addition of SO3 to be at the rate of 1 pound to the acre a 

 month at Mt. Vernon, Iowa, while Trieschmann,* over a 



^ Miller, K. H. J., The Amount of Nitrogen, as Ammonia and as 

 Nitria Add, and of Chlorine in the Sam-Water Collected at Eotham" 

 sted; Jour. Agr. Sci., Vol. I, pp. 280-303, 1905. 



^ Crowther, C, and Ruston, A. C, The Nature, Distribution and 

 lEffect Upon Vegetation of Atm^ospherie Impurities In omd Near an 

 Industrial Town; Jour. Agr. Sei., Vol. 4, pp. 25-55, 1911, 



^Peek, E. L., Nitrogen, Chlorine and Sulfates in Bain and Snow; 

 Chem. News., Vol. 116, p. 283, 1917. 



* Trieschmaim, J. E., Nitrogen and other Compounds in Bain and 

 Snow; Chem. News, Vol. 119, p. 49, 1919. 



