298 SYSTEMS OF PERMANENT AGRICULTURE 



"The samples of this material which have reached this laboratory have al- 

 most invariably exhibited a poor mechanical condition, the particles being 

 coarse and irregular in size. As the fineness of division of this phosphate has a 

 most important influence upon its availability to the plant, purchasers of this 

 material have been advised to only use the rock which has been pulverized to a 

 state of practical impalpability, the material in this condition being commonly 

 designated by the name of 'floats.' 



"A typical analysis of the raw phosphate rock sent to this laboratory this 

 season is given herewith : 



Citrate-soluble phosphoric acid 0.68 per cent 



Acid-soluble phosphoric acid 2 3-55 P er cen t 



Total phosphoric acid 24.23 per cent 



"It will be noted that nearly all of the phosphoric acid in this phosphate is in 

 an insoluble or acid-soluble condition, and there is SCARCELY A TRACE OF WATER 



SOLUBLE PHOSPHORIC ACID TO BE FOUND IN THIS RAW PHOSPHATE. 



"With regard to the comparative availability of raw phosphate rock, it might 

 be stated that the Experiment Station at Auburn has, during the past few years, 

 carried out under its supervision more than one hundred cooperative soil and 

 crop tests in a great many different localities in the State with a view to deter- 

 mining the comparative efficiency of raw phosphate and acid phosphate for fer- 

 tilizing purposes. These tests have been carried out upon quite a variety of 

 soils, and upon most soils the RAW PHOSPHATE HAS FAILED TO GIVE ANYTHING 



LIKE AS GOOD RESULTS AS THE ACID PHOSPHATE. 



"In the case of acid phosphate, the ready solubility of most of the phos- 

 phoric acid contained therein promotes its rapid and thorough distribution 

 through the top layer of the soil, and hence the plant food is so well dissemi- 

 nated that it is brought within easy reach of the root system of the plant, 

 whereas in the case of the crude insoluble phosphate the diffusion and dis- 

 tribution of the phosphoric acid is necessarily slow, and much of the phos- 

 phate is left unutilized at the end of the season in which it is applied. 



"For the above reasons IT is DEEMED INADVISABLE TO EMPLOY THE CRUDE 

 PHOSPHATE to any great extent upon any given soil until comparative tests of 

 the crude rock and acid phosphate have been made upon that soil, and, even 

 under these conditions, it will- probably be found necessary to use much larger 

 amounts of phosphate rock than are ordinarily employed to secure a satis- 

 factory return from its application." 



While the experience of the German Experiment Stations, combined with a 

 majority in this country, show emphatically that raw rock phosphate has 

 little or no fertilizing value, in addition the method of applying followed by 

 users of this material in this country is MOST EXTRAVAGANT AND WASTEFUL. 

 The method followed would soon exhaust the known or visible supply of 

 phosphate rock. Further, the enormous quantities necessary to apply per acre, 

 instead of being scattered over and benefiting millions of acres, would be wasted 

 on comparatively few. 



