82 MAINE STATE COLLEGE 



In table A are given the results obtained from the first tier of 

 plots. These furnish data on the comparative value of soluble 

 phosphoric acid in Dissolved Bone black and the insoluble phos- 

 phoric acid in fine ground bone and fine ground South Carolina 

 rock, also on the comparative value of commercial fertilizers and 

 stable manure. 



Both of these points are of great practical importance. The 

 phosphoric acid of dissolved Bone black is soluble but more 

 expensive than the insoluble phosphoric acid of fine ground bone 

 and South Carolina rock. It is believed that a large portion of 

 the soluble phosphoric acid becomes insoluble in water soon after 

 application to the soil On the other hand, it is believed that 

 there are agencies at work in the soil which make the phosphoric 

 acid of the mineral phosphate more available for plants as time 

 goes on. 



The question naturally arises whether manuring continuously 

 with insoluble mineral phosphate might not from a financial 

 standpoint prove more advantageous. 



It often happens that a farmer finds it desirable to cultivate 

 more land than he can manure well with the farm manures he has 

 at hand, and the question arises whether it will be better to pur- 

 chase stable manure at a neighboring village, or to make up the 

 deficiency with commercial fertilizers. 



