Nu. 6. 



DEPARTMENT OF AGRICULTURE. 



SS3 



The results obtained by the tests of both the ]\I;iine an*! Cornell 

 Experiment Stations are valuable in that they show the relative 

 ability of plants of various kinds to feed upon the different forms 

 of jjhosphoric acid. These results also show that upon soils which 

 are deficient in organic matter it is decidedly best with most crops 

 to use lome phosphate furnishing soluble phosphoric acid. Never- 

 theless, these results seem to point out that the insoluble phosphates 

 miglit be used on quite barren soils to grow such crops as turnips 

 or rape for soil renovation or green manure purposes. 



Again, these results, when considered in connection with the 

 results of field experiments made uj)on soil which contained a fair 

 amount of organic or vegetable matter, would seem to give addi- 

 tional evidence as to the necessity of having lands full of organic 

 matter in order to obtain good results from applications of insoluble 

 phosphates. 



SOME FOREIGN EXPERIMENTS WITH PHOSPHATES. 



Numerous experiments have been made from time to time upon 

 different phases of points effecting the availability of phosphates 

 and forms of phosphoric acid. To give an abstract from all of these 

 tests would not be possible in a work of this kind, yet it might be 

 interesting to note briefly a few which have been repeated recently 

 and which would seem to be closely related to the tests made in this 

 country. 



Experiments on the relative value of different phosphates, by Dim- 

 itry Prianischnihoff (Vol. 56 (1901), pp. 107-146, Landw. Versuchs- 

 Stationen). 



This was also a test of the relative ability of various crops to 

 use sparingly soluble phosphates. The tests were made by pot 

 culture in sand. The following numbers indicate the relative 

 amounts of phosphoric acid assimilated as shov/u by the results 

 up to the time of making the report: 



o 



Ph 

 W 



Cereals 



Buckwheat, lupens, etc. 



0-10 

 60 



40 

 90 



60-70 

 100 



100 

 100 



The summary makes the following statements: 



