June 16, 1919 Sulphates Affecting Plant Growth and Composition 



99 



Soil B responds to sulphur treatment in these pot tests while in the 

 field elemental sulphur caused no increase in production. In the analy- 

 sis of the soils in Table I soil C contains calcium carbonate, while B 

 does not. It may be that the sulphur was oxidized in the field as 

 in these pot tests, but as no base was present to combine with the sul- 

 phuric acid, the latter interfered with the growth. In C, calcium carbo- 

 nate was present which neutralized the acidity and provided sulphates 

 which produced the beneficial effects. Data in Table X show the differ- 

 ence in sulphate content between the soils receiving calcium carbonate and 

 sodium nitrate compared to those receiving the above named compounds 

 plus sulphur. The results show that the elemental sulphur was oxidized 

 to the sulphate form. Furthermore, no weighable quantities of barium 

 sulphate were obtained from, the water extracts of the unsulphured soils, 

 showing a deficiency of sulphate sulphur for immediate plant use. The 

 rate of sulphofication appears to be greater in the beaverdam soil than 

 in the other soils containing less organic material. While soil A has a 

 high sulphur content and also readily oxidizes elemental sulphur, it gave 

 a noticeable response to sulphate teatment when clover was grov/n. 



Table X. — Sulphur as sulphate in the water extract from 40 gm. of soil A and 80 gm. 

 each of B and C after growth of plants 



[Weight in milligrams] 



« Soil A = beaverdam; soil B=Medford loam; soilC=anteIope-clay-adobe. 



It is realized that the experiments conducted here have not been on a 

 large scale and the conditions are not comparable to those in the field. 

 No general conclusions can be made, but what conclusions are drawn 

 apply only to the limits of this experiment and based upon conditions 

 of this work where each individual case can be compared to the other. 

 This work will be repeated on a larger scale and expanded so as to 

 answer some of the questions which have arisen during this experiment. 



SUMMARY 



I . Pot experiments to show the effect of sulphur fertilizers — namely, 

 sodium sulphate, calcium sulphate and sulphur on red clover, rape, and 

 oats were carried with three different soils, including one with a high 

 sulphur content, one that did not respond to elemental sulphur in the 

 field, and one that did. 



