FURTHER STUDIES ON RELATION OF SULPHATES TO 

 PLANT GROWTH AND COMPOSITION 



By Harry G. M1L1.ER 

 Chemistry Department, Oregon Agricultural Experiment Station 



This is a continuation of an investigation, part of the results of which 

 were reported in a former pubHcation {4}} As stated in the earher paper, 

 the addition of the different forms of sulphur caused a marked increase 

 in the dry weight of red clover, and beneficial results were obtained with 

 oats and rape. One very noticeable result observed in the former work 

 was the high nitrogen content of the clover grown on soils in the green- 

 house receiving sulphur fertilizer, compared to that of clover receiving 

 only the residual sulphur of the soil. 



This great increase in nitrogen assimilation by the clover where sul- 

 phates were applied, and under the conditions described, led the writer 

 to believe that the sulphates favorably influenced the activity of the 

 legume bacteria. Especially did this appear true where the beaverdam 

 soil was used. This soil contained o. 18 per cent sulphur with appreciable 

 quantities of sulphate sulphur in the soil extract, and no beneficial result 

 from sulphur fertilizer was expected. Oats did not respond to sulphur 

 with this soil, although the sulphur content of oats (j) and the amount of 

 sulphur removed by one crop of oats is as large as with a red clover crop. 

 From present data, the responses of red clover so often obtained with 

 gypsum compared to cereals can not be explained through a difference 

 in sulphur requirement. With alfalfa the amount of sulphur removed is 

 so large compared to the cereals and red clover that the addition of 

 sulphates would apparently function directly as a plant food where in- 

 creased growth results. An example of the latter would be the enormous 

 increases in the yield of alfalfa obtained in southern Oregon (7) where 

 sulphur fertilizers were applied to soils with a very low sulphur content. 

 These authors, however, mention the favorable action that sulphur ferti- 

 lizers had on the root development and nodule production of alfalfa. 

 Duley (2) reports increase nodule production on red clover where sul- 

 phiu- was added to soils. Pitz (5) observed increased nodule production 

 and root development with red clover by applying gypsum to soil cultures. 



As far as the writer can ascertain, no correlation has been shown be- 

 tween nodule production and nitrogen content of the plant, by influencing 

 the development of the former, with ordinary sulphur fertilizer com- 

 pounds. In this paper a study has been made of the effect of different 



' Reference is made by number (italic) to "Literature cited," p. no. 



Journal of Agricultural Research. Vol. XXII, No. 



Washington, D. C. Oct. 8, 1921 



zt Key Na Greg. 7 



(lOI ) 



