30 Maine Agricultural Experiment Station. 1919. 



Watson farm Houlton a number of years ago in which home 

 mixed fertilizers were compared with standard commercial 

 brands of about the same analysis indicated very clearly that 

 not more than half of the nitrogen in a fertilizer should be de- 

 rived from the organic sources unless it was in a very easily 

 broken down material. Even good tankage when used in larger 

 amounts had a tendency to prolong the top growth until too 

 late for the short growing season of Aroostook County to al- 

 low time to develop the desired tuber growth. The formula 

 used by the Station in its potato growing is a fairly good one 

 • for general use in the County. In this formula one-third of the 

 nitrogen is from nitrate, one-third from sulphate of ammonia, 

 and one-third from high grade organic sources. 



EFFECT OF OMITTING POTASH FERTILIZATION 

 UPON THE POTATO CROP 



Since the introduction of potash in commercial fertilizers 

 in the early seventies of the last century, many experiments 

 have been made and many treatises written showing the value 

 of potash in crop growing. The experimental data on growing 

 crops without potash are very few. 



Potatoes are the chief cash crop grown in Maine. Fore- 

 seeing the possibility that, with the continuance of the war, 

 very little potash would be available for fertilizers, the Maine 

 Agricultural Experiment Station began in 19 15, at Aroostook 

 Farm, a series of experiments to determine the effect of dif- 

 ferent amounts of potash. The results obtained in 191 5 were 

 published in Bulletin 246; those for 1916 were published in 

 Bulletin 260, and those for 1917 in Bulletin 269. 



Five different mixtures were used. In each case the fer- 

 tilizers contained 5 per cent of ammonia of which one-third 

 was in the form of nitrate of soda, and 8 per cent of available 

 phosphoric acid. The potash varied as follows : On one plot 

 there was no potash. The next plot also had no potash but 

 common salt was mixed with the fertilizer at the rate of 300 

 pounds of salt per acre. The salt was used to see whether this 

 would aid in freeing potash already in the soil and not in a 

 form available for plant food. The fertilizer for the remaining 

 3 plots contained respectively 3 per cent, 5 per cent and 8 per 



