74 MAINE AGRICULTURAL EXPERIMENT STATION. 



It will be noticed that in this work only the immediate effect 

 of the phosphates has been taken into consideration, no mention 

 having been made of the unused phosphoric acid remaining in 

 the soil at the close of the experiment. In actual field work the 

 good effect of the ground rock would, of course, be far more 

 lasting than that of the acid rock. 



Box experiments were made at the New Hampshire Experi- 

 ment Station in 1893 with winter rye, the phosphoric acid being 

 supplied by roasted Redonda, ground bone, and basic slag. The 

 result showed that the rye gave nearly as good returns with the 

 roasted Redonda as with the other phosphates. This result con- 

 firms the work here reported. It will be seen by reference to 

 the diagram here given that the corn, barley, oats and timothy 

 (plants closely related to rye) gave better results with the 

 Redonda phosphate than with the finely ground Florida rock. 



SUMMARY. 



1. Plants differ in their ability to feed upon crude phosphates. 



2. Turnips, ruta-bagas, cauliflowers and kohl-rabi gave 

 nearly as good returns with the Florida rock as with the acid 

 rock. 



3. In every other case the good eff'ect of the acid rock was 

 very marked. 



4. In most cases the crude Florida rock yielded better returns 

 than the Redonda. 



5. Barley, corn and oats seem to require an acid phosphate. 



6. When early maturity is desired, the acid rock can profit- 

 ably be used. 



7. The largely increased production obtained b}' the use of 

 the acid rock will often determine the success of the crop. 



8. The solubility of a phosphate in ammonium citrate is not 

 always the correct measure of its actual value to the plant. 



