No. 6. DEPARTMENT OF AGRICULTURE. 865 



variance with the principles commonly taught and practice gener- 

 ally followed in the matter of fertilization. With these considera- 

 tions it would be well for those persons who desire to apply these 

 results or use any different source or form of phosphoric acid from 

 that which has been successfully and satisfactorily used in the 

 past, to do so on a limited scale in order to be satislied that these 

 results will hold under the new and different conditions which 

 may surround each particular case. 



The average total results, as given by the figures in Table 19, page 

 62, show that insoluble phosphoric acid, that is phosphates which 

 have not been treated or dissolved in sulphuric acid (oil of vitriol), 

 have more pounds of crop, both straw and marketable grain, than 

 the phosphoric acid in the soluble and reverted forms; that is, in 

 phosphates which have been dissolved iu sulphuric acid. Not only 

 has the yield produced by the insoluble phosphoric acid been greater 

 than that produced by the soluble phosphoric acid, but the cost 

 has been only about one-half as much. 



The results obtained show that crops are able to use the insoluble 

 phosphoric of South Carolina rock, notwithstanding the preaching 

 and contention of most fertilizing manufacturers. 



The results show that slag phosphate (which is mostly a tetra- 

 phosphate of lime, classed by some as available to crops, yet classed 

 by the American Official Methods of Analysis as mostly insoluble 

 phosphoric acid), gives a greater total yield than any of the other 

 insoluble phosphates. The yield of corn (grain), though not quite 

 as much with slag phosphate as with bone meal, yet was greater 

 with wheat and grass. All yields were produced at a less cost with 

 slag phosphates than with bone meal. 



Bone meal was the best form of insoluble phosphate for corn, 

 but its accumulative and supposed lasting effects did not show on 

 the wheat and grass. Bone meal has also had an advantage over the 

 other phosphates in furnishing some nitrogen. 



The results obtained show crimson clover to be the best crop to 

 use for obtaining organic matter in the soil in order to procure the 

 best results with the insoluble phosphates. 



SUMMARY OF PRINCIPAL, RESULTS OBTAINED FROM THE MARYLAND 



STATION EXPERIMENTS. 



1. All forms of phosphoric acid produced an increase of crop. 



2. The average total yield of the crops fertilized with insoluble 

 phosphoric acid was greater than those with the soluble and re- 

 verted forms of phosphoric acid. 



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