36 Maine Agricultural Experiment Station. 1918. 



It is evident as discussed above that ammonia is the limit- 

 ing factor on the soil test experiment field of the Station at 

 Aroostook Farm. Not only does ammonia give a higher result 

 than either phosphoric acid or potash but it gives a yield equal 

 to that obtained with a complete fertilizer. The yields from 

 the different plots N show potash as the limiting factor but with 

 some response from phosphoric acid and ammonia. The yields 

 obtained with potash equal those from the complete fertilizer 

 plots. With S potash gives increased yields while ammonia 

 and phosphoric acid do not. But the yields from the 3 potash 

 plots are much lower than from the complete plots. The yields 

 obtained by Y are not helped by ammonia, are helped some by 

 potash and markedly by phosphoric acid. But the complete 

 outyields the phosphoric acid. 



These 4 fields all with Caribou loam and situated near 

 each other in the Aroostook Valley indicate different values for 

 each of the fields. On A ammonia is the essential. On N it 

 is Potash that is needed. On S potash is the valuable constitu- 

 ent but it needs a complete fertilizer to bring the maximum 

 yield. While on Y phosphoric acid doubles the yield, ammonia 

 does not affect the yield and potash adds 50 per cent to the 

 yield. From this evidence on A one would expect ammonia to 

 be profitable. On N potash will be needed for results. On S 

 potash pays but the complete fertilizer gives the maximum 

 yields. On Y both potash and phosphoric acid are needed to 

 produce the maximum yields and ammonia has no effect. 



It is needless to say that no definite conclusions can be 

 drawn from these results. They are only one year's results and 

 as explained on page 18, it is planned to continue this work 

 through a long period of years. 



