USE OF PHOSPHORUS IN DIFFERENT FORMS 271 



As an average, the raw calcium phosphate produced more than 90 

 per cent as much increase as the common acid phosphate in the 

 various crops grown in 1901 on the unlimed land. 



The value of the increase produced by the raw calcium phosphate 

 in the hay crops alone is twice the cost of all the phosphorus ap- 

 plied in this form during the eight years. 



The value of the lime in the slag phosphate is indicated espe- 

 cially in the increase in hay on the unlimed land. The aluminum 

 phosphates (which also contain some iron phosphate) gave much 

 poorer results than the raw calcium phosphate; but no final con- 

 clusions should be drawn regarding this, because the aluminum 

 phosphate may not have been as finely ground as the common 

 rock phosphate, which in these experiments was applied as " floats," 

 the dust that collects about phosphate mills. There is evidently 

 no advantage from roasting the aluminum-iron phosphate (Re- 

 dondite). 



The somewhat poorer results obtained with the double super- 

 phosphate, as compared with the other three acidulated phosphates, 

 is probably due to the manufactured land-plaster (calcium sulfate), 

 which is a powerful soil stimulant, and which as already explained 

 constitutes about 50 per cent of ordinary acid phosphate. 



It will be noted that the lime itself more than doubled the yield 

 of hay as an average of all plots, and also increased the yield of 

 corn. This Rhode Island soil is acid, and for most crops is markedly 

 improved by liming. 



In commenting upon these experiments, Director Wheeler says 

 (Rhode Island Bulletin 114): 



"With the pea, oat, summer squash, crimson clover, Japanese millet (on 

 the unlimed land), golden millet, white-podded Adzuki bean, soy bean, and 

 potato (on the unlimed land), floats (raw calcium phosphates) gave very good 

 results; but with the flat turnip, table beet, and cabbage they were relatively 

 very inefficient." 



"The use of fine-ground bone, basic slag meal, and floats has tended con- 

 tinually to make the unlimed land more favorable to clover, as is well shown 

 by its appearance only upon those plots of the unlimed series where these 

 phosphates had been used, while it was absolutely lacking where the raw 

 and roasted Redondite and the soluble phosphates had been applied. Upon 

 the limed land, clover has been uniformly common upon all the plots." 



"Floats can probably be used to best advantage on moist soil, rich in decay- 



