USE OF PHOSPHORUS IN DIFFERENT FORMS 295 



Coming down to our country, we find that experiments with RAW ROCK 

 PHOSPHATE with scarcely any exception have proven unsatisfactory. 

 Experiments conducted by the Maine Experiment Station, covering several 

 years on various crops, designed to show the relative availability of phosphoric 

 acid as supplied in acid phosphate, floats (raw rock phosphate), and redonda 

 phosphate, were summarized as follows : 



"In every case the acid rock (Acid Phosphate) gave the best returns. The 

 gain was especially marked with the family Gramineae, three members of which 

 (barley, corn, and oats) yielded nearly double the amount produced by the 

 Floats or Redonda. The effect upon sunflowers and buckwheat was equally 

 marked. If we compare the amount of dry matter produced by the acid rock 

 with that produced by the Floats for all crops grown, we find the balance in 

 favor of the acid rock to be FIFTY-TWO PER CENT. In other words, the effect of 

 the available phosphoric acid as compared with the insoluble phosphate was to 

 increase the product MORE THAN ONE HALF." l 



The Georgia Experiment Station, commenting in Bulletin No. 2, concern- 

 ing field experiments with phosphates and kainit applied to cotton, states: 

 "Of phosphates, Acid Phosphate appears to lead, slag conies next, and the 



FLOATS ARE LAST." 2 



A later Georgia Bulletin (No. 31), in reviewing a comparison of superphos- 

 phate with Tennessee soft phosphate, states : "Superphosphate in a complete 

 fertilizer was compared with one, one and a half and two times the same amount 

 of Tennessee soft phosphate. The latter (Tennessee soft phosphate) was ap- 

 plied in each case at a loss." 2 



In the Annual Massachusetts Experiment Station Report for 1902, concern- 

 ing an experiment with various kinds of phosphates which were applied in 

 equal amounts of phosphoric acid, there is the following regarding raw rock 

 phosphate : "Tennessee phosphate and Florida soft phosphate gave results very 

 much inferior to all the others." This was an experiment on onions. 



In the Massachusetts Annual Report for the following year (1903), concern- 

 ing the same experiment continued on cabbages, the previous year's results are 

 confirmed: "That Tennessee phosphate and Florida soft phosphate proved 

 very much inferior to all others." 3 



1 This quotation is taken from page 72 of the 1898 Report of the Maine Experi- 

 ment Station; while on page 57 of the 1900 Report occur the following statements: 

 " For the first year the largest increase of crop was produced by soluble phosphoric 

 acid. For the second and third years, without further addition of fertilizers, better 

 results were obtained from the plots where stable manure and insoluble phosphates 

 were used. " C. G. H. 



2 These are single-year tests. The following quotation might also be made from 

 page 161 of Georgia Bulletin No. 25 : "Florida Soft Phosphate appears to be equally 

 as valuable as Acid Phosphate, the difference, if any, being rather in its favor. " 

 C. G. H. 



3 On the other hand, the South Carolina raw rock phosphate produced a much 

 larger yield than acid phosphate, especially of marketable cabbage, as shown in 

 Table 49. C.G. H. 



