June 26, 1916 Mineral Phosphates and Plant Nutrition 



507 



Table XVI. — Dry matter produced in timothy and red clover by Tennessee brown rock 

 phosphate and crop residues — series 11 



Timothy. 



Pot No. 



41a 



42. 



43- 

 44. 



45- 

 46,, 



47- 

 48., 



49- 

 so- 



Phos- 

 phate 

 added. 



Gm. 



22 

 22 



66 



66 



220 



220 



Organic 

 matter 

 added. 



Gm. 

 O 

 2.9 

 o 



24.4 



o 



32- 7 

 o 



61.6 



o 



67. 2 



Hay 

 yield. 



Gm. 



0. 25 



•05 

 . 02 

 . 20 



•30 



1. 10 

 3- 40 



10. 70 

 8. 70 



11. 70 



Red clover. 



72 

 73 

 74 

 75 

 76 



77 

 78 



Hay 

 yield. 



Gm. 



O. 02 

 . 10 

 .40 

 . 10 



2. 70 



6. 40 



4. 70 

 12.50 



" See series i, Tables II to VI. 



INFLUENCE OF SIZE OF PARTICLES ON THE AVAILABILITY OF PHOS- 

 PHORUS IN MINERAL PHOSPHATES 



The degree of fineness of rock phosphate particles has been held by 

 many irui^estigators to be an important factor in the availability of 

 mineral phosphates. Dr. Jordan, of the New York Experiment Station, 

 showed rather conclusivel}' that plants supplied with very finelv ground 

 rock phosphate contained more phosphorus and produced a greater 

 quantity of dry matter than those supplied with the coarser grades. For 

 the purpose of determining a comparative value of the same rock when 

 ground very fine to that left in particles of a larger size, series 12 (Table 

 XVII) was begun. As a check on the rock which was obtained from the 

 Mount Pleasant mills some lump rock from the same source was secured 

 and ground. These results are reported along with the data on the 

 influence of the size of particles on the availability. 



Table XVII. — Relation of size of phosphate particles to the availability of phosphorus by 

 Sixty-Day oats harvested on fuly 10, IQIS — series 12 



