32 



BROADBALK FIELD 



tion. The yield of the other three plots increases with each addition of 

 nitrogen ; the grain increases from 23 bushels with 43 lb. of nitrogen, 

 to 32 bushels with 86 lb. of nitrogen, and to 36 J bushels with 129 lb. of 



Total Produce 

 per Acre 



6000 lb— 



50OO 



400O 



3000 



Straw per Acre J b. 



Grain per Acre Jb 



Fio. 9. — Comparison of Nitrate of Soda and Ammonium-salts on Wheat. 



Ten years (1893-1902). All Plots receive Minerals alike. 



The figures in the labels indicate bushels of Grain and cwt of Straw. 



nitrogen ; the straw is even more affected by a free supply of nitrogen, 

 rising from 21 J cwt. to 33 and 41 cwt. as the nitrogen is doubled and 

 trebled. 



Comparative Effect of Nitrate of Soda and Ammonium-salts. 

 Plot 6 should be compared with Plot 9, and Plot 7 with Plot 16. 

 Plots 9 and 16 receive nitrate of soda and mineral manures, so that 



