82 BTTLLETIN 699, U. S. DEPARTMENT OF AGRICULTUKE. 



largest yields, closely followed, however, (and in one case equaled) 

 by the basic-slag pots. The raw rock phosphate pots produced an 

 appreciable increase in yield over the no-phosphate pots, but far less 

 than any of the other treated pots except those receiving sodium 

 phosphate. This latter compound, it is said, seemed to have a toxic 

 effect. 



In experiment No. 2, where a soil was employed, the raw-rock pots 

 gave little or no increase over the checks, while those treated with 

 basic slag produced in most instances greater yields than the acid 

 phosphate pots. 



The data obtained in these pot experiments, however, are of such 

 limited value (owing to their short duration, and also to the fact 

 that only a single crop was tested) that the writers have hesitated to 

 present them, but as far as they go they indicate that liberal appli- 

 cations of phosphoric acid in the form of acid phosphate and basic 

 slag were superior to twice the quantity in the form of raw rock 

 phosphate. 



NEW YORK. 



The first three experiments ^ conducted by the New York Experi- 

 ment Station with raw rock phosphate as a fertilizer were of such 

 short duration and the data presented are so limited that they are 

 not considered in detail in this bulletin. 



In some pot or greenhouse experiments conducted by the Geneva 

 station from 1896 to 1900 sufficient data are given to warrant a repe- 

 tition of the figures and a discussion of some of the details. 



The soils in which the plants were grown in the several experi- 

 ments were as follows: 



In 1896-97 a natural sandy pine land soil, supposedly poor, was 

 used (110 pounds per box). In 1898-99 quartz sand containing from 

 99.5 to 99.7 per cent SiOa was employed (46 pounds per box with 12 

 pounds of coarse material for drainage). In 1899-1900 for some 

 crops the same sand which had been used during the previous year 

 after removing roots and organic matter and for some crops an equal 

 quantity (46 pounds) of fresh sand. 



Adequate quantities of readily available nitrogen and potash car- 

 riers were added in each case and the same amount of phosphoric 

 acid was a^ded to each can or box in the forms given in the table. 

 The effect of these phosphates on the yield of several orders of plants 

 was studied by running each treatment in duplicate. 



IN. Y. Agr. Expt. Sta., 7tli Ann. Rept., pp. 356-363 (1889) ; 8th Ann. Kept, pp. 

 256-258 (1890) ; Cornell Buls. Nos. 143 (1898) ; 166 (1899) ; 182 (1900) ; 201 (1902). 



