New York Agricultural Experiment Station. 251 



grown in the same boxes without renewal of the supply of phos- 

 phates for the second and third crops. In 1903-4 with a more 

 favorable and efficient artificial soil, due to the introduction of 

 sphagnum moss, the experiments were much more successful. 

 The crops used were barley, peas and rape. 



In all cases the plants were allowed to attain the fullest develop- 

 ment that seemed to be possible under the conditions involved, 

 which in the case of barley, peas and rape was quite satisfactory. 



The preceding tables show the yield of dry matter, the quan- 

 tities of Pi0 5 taken up from the acid phosphate and from the 

 raw phosphate of the different degrees of fineness, and the re- 

 lation in quantity of the P 2 5 used to the dry matter produced. 

 In the case of the barley in 1899-1900 the yield was so small, 

 excepting with the acid phosphate, that the content of P 2 5 in 

 the crop was not determined. 



Certain facts revealed in the above figures are worthy of com- 

 ment. 



The results as a whole clearly show that fineness of division has 

 an important influence upon the availability of raw ground 

 phosphate rock. This does not appear in any striking way with 

 the rape of 1899-1900, but in the second season's tests (1903-4), 

 with all three crops used, the P 2 5 assimilated increases quite 

 uniformly with the degree of fineness. In the case of bone, 

 fineness seemed to have small influence on availability, at least 

 within the limits tested. 



The fineness of the ground rock and bone had small influence 

 on the growth of dry matter in the various crops. The plants 

 seem to have secured enough phosphoric acid from even the 

 coarsest materials to satisfy the demands of the maximum growth 

 possible under the conditions established. This means that the 

 proportion of phosphoric acid to dry matter increased with the 

 fineness of division of the ground rock. The amount of phos- 

 phoric acid assimilated from the acid phosphate was notably 

 greater than what was appropriated from the undissolved rock, 

 even though the growth of dry matter was but little, if any, larger. 



