Maine Agricultural Experiment Station. 1917. 



Ill 



in grain for the 2 preceding- years, and in each year had received 

 500 pounds per acre of a fertihzer carrying 7 per cent potash. 

 On account of the difference in treatment of the preceding 

 crops these 2 series of plots will be considered separately. 



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

 tilizers contained 4 per cent of nitrogen (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 fertil- 

 izer 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 but not in a form available for plant food. The 

 fertilizer for the remaining three plots contained respectively 

 2 per cent, 5 per cent and 8 per cent potash. In each case the 

 fertilizer was applied at the time of planting, at the rate of 

 1500 pounds per acre. Each plot was slightly less than one-half 

 acre in area. The area of each plot was obtained by actual 

 measurement and the yields are based on the weighed potatoes 

 from each plot. Norcross potatoes were used for seed. Other 

 than in respect to potash all plots were treated exactly alike. 

 Series I. The land on which this series of plots was lo- 

 cated was in potatoes in 1912. It had been in grass for 2 years 

 without any fertilizer. The following are the results obtained, 

 expressed in yields per acre. 



Yields per Acre in No Potash Experiment With Potatoes, 



Series I. 





Amount of P -tash 



Merchantable 



Culls 



Plot No, 













Bbls. Bus. 



Bbls. 



Bus. 



436 



Non? 



T"-)/! 287 



4.6 



13 



437 



Ncno + common salt 



nf!.7 321 



3.0 



8 



438 



2 par cent 



154.0 423 



2.0 



6 



439 



5 p"r cent 



7P3,fi 429 



1.7 



5 



450 



8 pn- C5nt 



!-lT,7 401 



3.1 



9 



Series II. The land on which this series of plots was 

 located was in potatoes in 1913. In both 1914 and 1915 this 



