NITRATE VERSUS AMMONIUM- SALTS 45 



return in the crop. Thus Plot 6 with 43 Ib. of nitrogen gives 

 81 bushels more than Plot 5 with no nitrogen, another 43 Ib. 

 of nitrogen on Plot 7 produce a further increase of 8 '9 bushels, 



Total Produce 

 ^ per Acre 

 6000 Ib. 



4OOO 



3000 



Plot 



(Straw per Acre, Ib. 



Gram per Acre, Ib 



FIG. 4. Comparison of Nitrate of Soda and Ammonium-salts on Wheat. 

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



whereas the next addition of 43 Ib. of nitrogen only produces 

 an increase of 4*2 bushels. 



During the first 13 years of the experiment one of the plots 

 received a still further addition of nitrogen, making 172 Ib. in 

 all. The Table (XVII.) shows the yield of grain and straw of 



