Oct. 8,1921 Relation of Sulphates to Plant Growth and Composition 105 



TablS II. — Analytical results with red clover on beaverdam soil 



Treatmeat. 



Control 



CaSOi and NaNOs. 



CaS04 



NaN03 



NasSOi 



Na2S04 and NaNOs 



S 



SandNaNOs 



Crop I. 



Weight 

 of air- 

 dried 

 clover. 



Gm. 

 46 



46 



Total 



N. 



P. a. 



3-28 

 3- SO 

 3-41 

 3-25 

 3-47 

 3- 12 

 3-42 

 3-58 



Total 

 S. 



P.ct. 



Crop II. 



"Weight 

 of air- 

 dried 



clover. 



Gm. 



102 

 91 



80 

 83 



Total 



N. 



P.ct. 



2. 70 

 2. so 

 2. 40 

 2-53 

 2.49 

 2.47 

 2. 56 



Total 

 S. 



P.ct. 



Cropni. 



Weight 

 of air- 

 dried, 

 clover. 



G.m 



69 

 66 



Total 



N. 



Total 



S. 



Sul- 

 phate 

 S. 



P.ct. 



o. 02 



Or- 

 ganic 

 S. 



P.ct. 



O. 12 



•15 

 . 12 

 •13 



Treatment. 



Control 



CaS04and NaNOs.. 



CaS04 



NaNOs 



Na2S04 



Na2S04 and NaNOs. 

 S. 



S and NaNOs. 



Crop IV. 



Weight 

 of air- 

 dried 

 clover. 



Gm. 



Total N. 



Per cent. 



3- 16 



Total S. 



Per cent. 

 18 



Sulphate 

 S. 



Per cent. 

 03 

 15 

 12 

 06 



Organic 

 S. 



Per cent. 

 IS 

 IS 

 IS 

 16 



.16 

 16 

 14 



.16 



Bxammation of the foregoing data shows no result from sulphate 

 application in the first two crops. There is no increase in dry weight 

 in the pots receiving sulphur fertilizers, and in some crops the yield on 

 the control is greater. In the third and fom'th crops, one distinctive 

 difiference appears in the lower nitrogen content of the clover grown on 

 the control soil cultures. The fact that the clover grown under condi- 

 tions supplying more sulphate sulphur has a higher nitrogen content 

 adds to the data already obtained pertaining to the favorable influence 

 that sulphates have upon legume bacteria, the action of which results 

 in a higher nitrogen content of the clover. According to experimental 

 evidence, sulphates do not increase nodule production on all legumes. 

 Wilson (8) reports that certain sulphates depressed nodule formation 

 on the soybean. On the other hand, Prucha (6) mentions magnesium 

 sulphate and calcium sulphate as exerting a beneficial influence on nodule 

 development of the Canada field pea. 



The low nitrogen content did not appear to be due to the absence of 

 sulphates in the plant tissue, thus limiting protein synthesis, as sulphates 

 were present in all samples. However, the percentage of sulphate 

 sulphur was lower in clover grown on the control pots. 



That the presence of available nitrogen or nitrogen assimilation by 

 the plant tends to control or limit the total sulphur assimilation is illus- 

 trated by data in Table III, 



