66 



BULLETIN 699, U. S. DEPARTMENT OF AGRICULTURE. 



In order to see at a glance the apparent relative values of the 

 various phosphates used in this experiment, the Maryland station 

 compiled a table in which the yields given in Tables XXXIV and 

 XXXV were reduced to a percentage basis, talring the yield of the 

 Virginia phosphate plot as 100. The results are given in Table 

 XXXVI. It will be noted that the average production of the differ- 

 ent plots after the application of the phosphates was less than before 

 the treatments, but since the greatest decrease in yield was on the 

 check plots, it is assumed that the phosphates had a beneficial effect. 



The figures in the column headed " Relative increase " represent 

 the average relative increases of the various phosphate plots over the 

 check plot. 



Table XXXVI. — Relative yields and average inruence of different forms of 

 phosphoric acid, expressed in percentages. 



Phosphate treatment, 150 pounds PjOs per acre, in 

 the following forms: 



Rate of 

 yield 

 before ex- 

 periment. 



Rate of 

 yield 

 during ex- 

 periment. 



Eifference. 



Relative 

 increase. 



Groimd South Carolina rock 



Dissolved South Carolina rock 



Dissolved South Carolina rock and lime . 



Check (no phosphate) 



Ground Tennessee rock 



Ground Flcirida rock 



Ground Virginia rock 



Precipitated phosphate 



Per cent. 

 83 

 72 



91 

 100 



Per cent. 

 73 

 72 

 74 

 77 

 91 

 98 

 100 

 93 



Per cent. 

 -10 





 -12 

 -20 

 - 6 

 + 7 





 + 5 



Per cent. 



Apparently the greatest effect was produced by the Florida soft 

 phosphate and the precipitated phosphate treatments. The Virginia 

 phosphate (which, it is said, was largely a phosphate of aluminum) 

 and the acid phosphate (without lime) came next with the same rela- 

 tive increase. Contrary to popular belief the application of lime in 

 connection with acid phosphate did not in this experiment appear 

 to be beneficial. 



The Maryland station results as a whole may be said to indicate 

 that applications of the relatively insoluble phosphates in a finely 

 divided or precipitated condition increase crop yields as effectively 

 in some instances as the more soluble phosphates. 



MASSACHUSETTS. 



In 1890 the Massachusetts station undertook an experiment^ to 

 compare the relative fertilizer merits of acid phosphate (dissolved 

 bone black) and some of the less soluble phosphates when the various 

 forms were applied in quantities representing at that time equal 

 money values. 



The field selected for this experiment was quite level and had been 

 used as a meadow up to 1887. The soil was a fair sandy loam, but 



1 Mass. Agr. Expt. Sta., 8th, 9th, 10th, and 11th Ann. Repts. 

 14th Ann. Rept. (1902). 



Hatch Agr. Expt. Sta., 



