68 



BULLETIN 699, U. S. DEPAETMENT OF AGEICULTUEE. 



It will be seen that while dissolved bone black led for the first 

 two years, during the remainder of the experiment several of the 

 relatively insoluble phosphates forged ahead, phosphatic slag being 

 first, South Carolina floats second, and Mona guano third. Florida 

 ground rock phosphate, however, gave relatively poor jdelcls when 

 compared with the plot treated with South Carolina floats. 



In Table XXXVIII the average relative rank of the various 

 plots from the beginning of the experiment, until it was discon- 

 tinued in 1902, are expressed on a percentage basis. 



Table XXXVIII. — Average relative rank of the plots treated with various 

 phosphates ^ (equal money values) during the 12 years ^ of the experiment. 



Treatment. 



Basic (phosphatic) slag 



Ground South Carolina rock. 



Dissolved bone black 



Mona guano 



Florida phosphate rock 



No phosphate (6 years) 



Per cent. 



100.0 

 92.6 

 89.7 

 87.3 

 71.1 

 55.4 



1 No phosphates applied after the third year. 



2 The crop of Swedish turnips grown in 1897 is not included, since it 

 was damaged by disease. 



Whi,le the basic slag and ground South Carolina phosphate plots 

 led all the rest in this experiment, the dissolved bone-black plot was 

 not far behind. 



Brooks ^ considers that the phosphates in this experiment were ap- 

 plied in a very irrational manner and in a way favorable to the rela- 

 tively insoluble varieties, but even under these conditions he con- 

 cludes that the data do not prove that the less soluble were more 

 effective than the readily soluble phosphates since the yields from the 

 Mona guano and Florida phosphate plots (particularly the latter) 

 were materially less than that of the acid phosphate plot. 



While the writers feel that the data obtained are hardly sufficiently 

 consistent to warrant a definite conclusion regarding the relative 

 merits of the various phosphate carriers, nevertheless they are of the 

 opinion that the method of applying phosphates in this experiment 

 was considerably more logical from an economic standpoint than 

 that employed in the subsequent experiment of the Massachusetts 

 station upon which Brooks lays much greater stress. 



In 1897 a second experiment - was undertaken by the Massachu- 

 setts station to test the fertilizer value of various phosphates when 

 they were applied in such amounts as to furnish equal quantities of 

 phosphoric acid to the soil. 



iMass. Agr. Bxpt. Sta., Bui. No. 163, pp. 147-148 (1915). 

 "Hatch Agr. Eipt. Sta., 10th Ann. Eept. (1898). 



