EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



85 



It is evident from the figures given in Table LI that the more finely 

 raw rock phosphate is ground the more effective it becomes. The 

 floats in almost every instance produced appreciably greater yields 

 than the coarser phosphatic material. The same is true, though to 

 a less extent, of bone meal. 



■ In the first experiment (1899-1900) where no organic matter was 

 applied, the pots treated with acid phosphate showed greater yields 

 than those treated with the less soluble phosphates, but in the second 

 experiment where organic matter was added the very finely ground 

 raw rock and floats gave as good and better yields than the acid phos- 

 phate, although it was supplied in quantities far less than phos- 

 phates occur in most soils. 



One other pot experiment to test the fertilizer value of several 

 relatively insoluble phosphates on barley was conducted by the 

 Geneva ^ station in 1912. 



The same artificial soil employed in the previous experiments was 

 used in this test, but the quantity of phosphoric acid added to each 

 pot in the various forms was from two to four times as great. Ade- 

 quate amounts of potash and nitrogen were added to each pot, but 

 no organic matter was employed. Each treatment was run in dupli- 

 cate. 



The average results of this experiment are given in Table LII. 



Table LII. — Yields of barley obtained in a pot experiment' (58.9 pounds of 

 soil) mth various phosphatic fertilizers ; potash and nitrogen supplied to all 

 pots. 



Form of phosphates. 



Amount of 



P2O, 



added 



per pot. 



Yield of 



barley per 



pot. 



MnnnnalmnTn phnsphf^tfi 



Grams. 

 5.82 

 5.82 

 5.82 

 5.82 

 5.82 



Grams. 

 71.0 



Iron ore waste 



44.2 



Basic slag 



68.7 



(rrnnnd Tp.nnp.ssp.fi rnnlr . , , , , , 



55.7 



Bone 



74.7 



Blanks 



38.2 









The monocalcium phosphate, bone, and basic-slag treatments all 

 gave yields of barley greater than the ground Tennessee rock, but 

 apparently this crop was able to utilize to a certain extent the phos- 

 phoric acid of this latter material. 



In view of the fact that barley in previous experiments has not 

 responded readily to the less soluble forms of phosphoric acid when 

 they were present in small quantities, the results of this experiment 

 are not surprising, for while greater amounts of phosphoric acid 



^N. T. Agr. Bxpt. Sta. (Geneva). 

 358, pp. 252-253 (1913). 



Fertilizer Value of An Iron Ore Waste. Bui. No. 



