22 The Bulletin 



N. P. PRATT LABORATORY. 

 Cektificate of Analysis. 



Atlanta, Ga., June 29, 1915. 

 Sample No. 45809. 

 Received June 7, 1915. 



Marked: Acid Phosphate 30 days old, from Old Dominion Guano Company. 

 For N. P. Pratt, Atlanta, Ga. 

 Contains: 



Moisture 10.39 per cent. 



Composition of the water-soluble filtrate expressed in per cents of original 

 sample. 



Total calcium oxide 8.35 



Total aluminum oxide 38 



Total ferric oxide 33 



Total sulphur trioxide 7.22 



Total phosphorus pentoxide 



Equivalent to 18.28 



Sulphur trioxide combined in calcium sulphate 12.28 



P205 combined in monocalcium phosphate 9.60 



P205 combined in aluminum phosphate 66 



P205 combined in ferric phosphate 29 



PZ05 uncombined (free phosphoric acid) 7.73 



Respectfully submitted, 



(Signed) N. P. Pratt Laboratory. 



It has been shown that the net results of the teachin^r of Extension Circu- 

 lar No. 24 concerning the use of caustic lime rather than carbonate lime was 

 to cut off the cheap, native supply of soil nitrogen and force the farmer into 

 the fertilizer market to purchase high-priced ammoniated goods with which 

 to furnish commercial nitrogen to grow his crops. 



It will now be seen that the net results of its teaching, in opposition to the 

 mixing of limestone with acid phosphate, is to force the farmer to purchase 

 many times as much acid phosphate as his crop can get a chance to utilize, 

 and thus increase his fertilizer cost without proportionately increasing the 

 yield. 



On the other hand, the net result of the teachings of Bulletin No. 220 is the 

 building up of the soil humus and the conse(|uent increasing of the native 

 supply of soil nitroaen; the liberation and utilization of a part of the enor- 

 mous supi)ly of nalive potjish, and the increasing of the efficiency of the ap- 

 plications of commercial forms of ]»hosphate. 



The advice in Bulletin No. 220 will decrease the cost and increase the 

 efficiency of fertilizers; the advice in Extension Circular No. 21 will increase 

 the cost and decrease the efiiciency. Bulletin No. 220 will build up the agri- 

 culture of the State and render the farmers independent in their own homes; 

 Extension Circular No. 24 will decrease the prodncUve capacity of the soils 

 and make the farmers slaves to commercial plant foods. 



