240 



Journal of Agricultural Research 



Vol. V, No. 6 



renewed unlimed soil with the usual complete-fertilizer treatment. Crop 

 D was grown on soil which had borne two successive fertilized crops of 

 rape and two successive crops of turnips (Brassica naptis), the last crop 

 of turnips only receiving fertilizer. This clover crop was limed and 

 fertilized. All the crops were allowed to reach the late-blooming stage, 

 but they failed to produce seed. The roots of crops B and C were 

 separated as carefully as possible from the soil and weighed separately 

 from the tops. The yields of air-dried matter are given in Table 11. 



Table II. — Average weights {in grams) of air-dried clover crops 



In the yield of hay there was no doubt about a marked stimulating 

 effect of both sulphates upon growth. Stimulation was equally evident 

 when they were added to the complete-fertilizer treatment and w^hen they 

 were applied alone. In both cases the best results were produced by the 

 less soluble calcium sulphate. Elemental sulphur had a very depressing 

 effect. The average yield from this treatment was but little more than 

 one-third the yield from the control, and in crop D the clover entirely 

 failed to grow where elemental sulphur was applied. Plate XX, figure i, 

 illustrates the influence of sulphates on the growth of clover. 



Root development from the complete-fertilizer treatment was depressed 

 somewhat when sodium sulphat^e was also applied, but was unaffected 

 when the calcium sulphate was added. We are inclined to ascribe this 

 difference to the depressing effect of the more concentrated soil solution 

 where the soluble sulphate was applied. The effect of the sulphates 

 applied alone was very striking. In Plate XXI is shown the remarkable 

 difference of root development from the different fertilizer treatments. 

 From our limited amount of data calcium sulphate appears to be some- 

 what more active than sodium sulphate in producing this effect. In 

 any case it appears that in this soil a sulphate has specific effects on 

 the root development of this species. This may properly explain the 

 oftentimes beneficial effects observed in the application of land plaster 



