28 a 



EXPERIMENT STATION, 



[Jan. 



Comparison of Different Phosphates. 



This experiment was begun in 1897, and has for its object a 

 comparison of ten different materials that may be used as 

 sources of phosphoric acid. The data for the first eighteen years 

 of the experiment were published in Experiment Station Bulle- 

 tin No. 162. 



The materials furnishing phosphoric acid are applied in suffi- 

 cient quantity' to supply 96 pounds per acre of actual phosphoric 

 acid. Each plot receives an annual application of the following 

 mixture furnishing nitrogen and potash: — 



Pounds 

 per Acre. 



High-grade sulfate of potash, 160 



Nitrate of soda, 364 



Sulfate of ammonia, 100 



Hoof meal,i 102 



The crop this year was Medium Green soy beans. Owing to 

 an early frost the crop did not yield as well as usual. The fol- 

 lowing table gives the results obtained : — 



(Soy Beans (Yields per Acre). 



Plot. 



Phosph.\te. 



Beans 

 (Bushels). 



Straw 

 (Pounds). 



No phosphate, 

 Arkansas rock phosphate, 

 South Carolina rock, 

 Florida soft rock, . 



Slag 



Tennessee rock, 

 No phosphate. 

 Dissolved boneblack, 

 Raw bone. 



Dissolved bone meal. 

 Steamed bone. 

 Acid phosphate, 

 No phosphate. 



16.66 

 16.86 

 13.00 

 15.34 

 18.48 

 15.17 

 17.86 

 18.97 

 18.55 

 18.93 

 17.69 

 19.00 

 18.58 



4,234 

 4,222 

 3,526 

 3,750 

 6,848 

 3,640 

 5,044 

 5,060 

 5,444 

 5.062 

 4,974 

 4,498 

 3,322 



1 Plots 9, 10 and 11, which receive phosphoric acid in some form of bone, receive only enough 

 hoof meal to equalize the organic nitrogen. 



