142 



MAINE STATE COLLEGE 



The pLosphates used in the pot experiments were of the same 

 kind and composition as those used in the field experiments. 



The tables below show the kinds and amounts of fertilizers 

 supplied to each pot and the amount of grain and straw product : 



Khid and quantity of fertilizers. 



o 



O 



6 





03 



S s 



bX)g 



3 grams muriate of potash, ) 



16 

 20 

 24 



2 



6 



10 



3 



7 

 11 



22.88 

 18.85 

 24.37 



3.19 

 1.72 



2.74 



5 60 

 6.75 

 6.98 



67 



10 ■' nitrate of soda, > 



72 



10 " acid S. C. rock. J 



65 



3 fframs muriate of potash, ) 



12 ■ 



10 " nitrate of soda, > 



5 



5.5 " S. C. rock. j 



10 



3 grams muriate of potasli, ) 



15 



10 " nitrate of soda, V 



17 



4 " Caribbean Sea guano, j 



15 







The average yield of oats in pots 16, 20 and 24 was at the rate 

 of 128 bushels^ per acre, showing that these pots received plant 

 food of all kinds in quantities sufficient to produce a good crop. 



Pots 2, 6 and 10 received the same amounts of potash and 

 nitrogen and twice as much insoluble phosphoric acid as 16, 20 

 and 24 had of soluble phosphoric acid. The average yield of 

 grain however was only at the rate of about 15 bushels per acre. 



Pots 3, 7 and 11 were treated the same as 2, 6 and 10 with the 

 exception that the same quantity of phosphoric acid was furnished 

 in Caribbean Sea guano instead of South Carolina rock. The 

 average yield of grain was at the rate of 37.8 bushels per acre. 

 The depression of the yield caused by the substitution of the 

 crude phosphates for acid South Carolina rock may have been in 

 part due to the fact that the acid phosphate contained a consider- 

 able portion of sulphate of lime which the crude rock could have 

 carried only to a slight degree. The principal cause of the 

 depression, however, is believed to be due to the inability of the 

 plants to obtain a sufficient amount of phosphoric acid to produce 

 a maximum crop from the materials presented. Let the cause of 

 the depression be what it may the experiment leaves little room to 

 doubt that a considerable amount of phosphoric acid was obtained 



