1901.] PUBLIC DOCUMENT — No. 33. 105 



bages on the natunil phosphates, the yields have not been 

 what could be considered o'ood. 



3. Between ground South Carolina rock, ]\Iona guano and 

 the phosphatic slag there is no considerable ditterence in the 

 economic result. 



4. The Florida phosphate, though used in amounts fur- 

 nishing much more phosphoric acid than is furnished by 

 either of the others, stands far behind them in yield, and 

 would appear, therefore, to be rendered availal)le only with 

 extreme slowness. 



In conclusion, it may be doubted whether, under the con- 

 ditions prevailing in ordinary farm or garden practice, it 

 would be wise to depend exclusively upon the natural phos- 

 phates. The best practice will probably be found to consist 

 in using one of these in part, and in connection with it a 

 moderate quantity of one of the dissolved phosphates. 



VI. — Comparison of Phosphates on the Basis of Equal 

 Application of Phosphoric Acid. 



The phosphates under comparison on this l^asis include 

 apatite. South Carolina rock phosphate, Florida soft phos- 

 phate, phosphatic slag, Navassa phosphate, dissolved bone- 

 black, raw bone, dissolved bone, steamed bone and acid 

 phosphate. The experiments have been in progress three 

 years, each phosphate being applied yearly to the same plot. 

 There arc three no-phosphate plots, which serve as a basis for 

 comparison. The plots are one-eighth of an acre each in area. 



During the past year two crops have been grown upon 

 this field : oats, which were cut and made into hay ; and 

 Hungarian grass, also made into hay. The yields have been 

 large on all plots, varying from a little less than 4 tons per 

 acre for the two crops on the poorest no-phosphate plot to 

 rather over 5 tons per acre for the two crops on the dissolved 

 bone-black which gave the largest yield. The only points 

 to which it seems desirable to call attention are the follow- 

 ing : — 



1. The phosphatic slag evidently furnished phosphoric 

 acid in an exceedingly available form, the yield this year 

 being almost equal to that on the dissolved bone-black. 



