1917] SOILS FERTILIZERS. 119 



of the two filtrates, and that the action of the acids set free by adsorption of 

 bases is important in this connection. 



It is concluded best, therefore, to consider an acid soil as one not saturated 

 \vith bases. 



The sulphur content of some typical Kansas soils, and the loss of suiphur 

 due to cultivation, C. O. Swanson and R. W. Miller {Soil Sci., 3 (1917), No. 

 2, pp. 139-1 JfS). — Studies of the sulphur content of eleven samples of typical 

 Kansas soils made at the Kansas Experiment Station are reported. The soils 

 are loams, silt loams, and silty clay loams. Five were from fields in the native 

 sod and six from fields in cultivation for from 30 to 40 years. 



The results " show that the percentage loss of sulphur from cultivated soils 

 is proportionately equal to that of organic matter. It has also been shown 

 that the los.s of sulphur due to the amount taken up by the crop is insignificant 

 as compared with the total amount which has disappeared from the soil. This 

 means that the sulfofication has been in excess of the needs of the crop and the 

 sulphates produced have leached out of the ground. As measured by crop 

 requirements, sulfofication has been much more rapid than nitrification." 



It is further concluded that the loss of sulphur from soil may be a very 

 important factor in the loss of productivity. " Whether or not sulphur is at 

 present a limiting element in the production of crops on Kansas soils, it is 

 apparent that the supply of this essential element is closely related to the 

 supply of organic matter. ... It would seem that sulphur would become a 

 limiting factor sooner than phosphorus unless sulphur is made available more 

 rapidly than phosphorus. This, however, would not affect the ultimate supply." 



Sixteen references to literature bearing on the subject are appended. 



Studies in sulfofication, P. E. Brown and H. W. Johnson (Iowa Sta. Re- 

 search Bui. 34 (1916), pp. 3-24). — Continuing previous work (E. S. R., 34, p. 

 19), experiments on the relative effects of gj'psum, acid phosphate, rock phos- 

 phate alone and with gypsum, and monocalcium phosphate, on sulfofication and 

 on ammonification and the yields of oats in pots are i-eported. The soil used 

 was a black loam, high in organic matter and of basic reaction. 



It was found that " the sulphate content of the soil varied only slightly from 

 one sampling to the next. There were no sudden or striking changes in the 

 amount of sulphates present in soil kept fallow in the greenhouse. The sulphate 

 content of soils in the field is subject to the same influences as the nitrate con- 

 tent, but the effects are probably much less pronounced. 



" Calcium sulphate, monocalcium phosphate, acid phosphate, rock phosphate, 

 and rock phosphate plus gypsum increased the sulfofying power of the soil. 

 The sulphate alone and phosphates alone had greater effects than combinations 

 of the two materials as in acid phosphate. All the materials used increased 

 the ammonifying power of the soil, but the differences between the effects of 

 the various substances were not pronounced. The rock phosphate had less 

 effect, however, than the other materials. The sulfofication tests and ammoni- 

 fication tests did not always run parallel, although very similar effects of the 

 materials used, on the two processes, were noted. The phosphorus fertilizers, 

 except monocalcium phosphate, increased the yield of oats on the soil, the acid 

 phosphate to a greater extent than the rock phosphate. The sulphate had no 

 effect on the crop yield. . . . 



" The crop yields, sulfofication, and ammonification results were not always 

 parallel. In general, it appeared that on this soil increases in sulfofication 

 were not necessarily parallel with increases in yields. The ammonification 

 results were not conclusive but indicate that materials supplying plant food 

 constituents which are lacking in the soil may be of double value because of 



