104 



EXPERIMENTS UPON ROOT-CROPS 



Plots 8, 5, 6, and 4 ; the first column in each group represents 

 the mean crop for twenty-seven years on Plot 8, receiving no 

 mineral manures; the second column represents the crop of 

 Plot 5, receiving superphosphate only; the third, that of 



Series 







With 



No Nitrogenous 

 Manure. 



D 



NoMinerals. 



N 



With 

 Nitrate 

 of Soda. 



771 



^Superphosphate . 



A 



With 



Ammonium 

 Salts. 



^Superphosphate 

 ; : . : -:1 and Potash . 



AC 

 With 



Rape-cake A 

 Ammonium Salts. 



IS u perph osphate , Potash , 

 Magnesia and Soda. 



FIG. 15. Mangolds. Effect of various Mineral Manures. Average 

 Produce of Roots per acre, 1876-1902.* 



Plot 6, with potash in addition to the superphosphate ; and 

 the last column represents the crop of Plot 4, which receives 

 superphosphate and all the alkalies potash, magnesia, and 

 soda. The four plots in each series are grouped together. To 

 the first group (0) no nitrogenous manure is applied ; in the 

 second (N), nitrate of soda ; in the third (A), ammonium- salts ; 

 in the fourth (C), rape cake ; and in the fifth (AC), rape cake 

 and ammonium- salts, are respectively the sources of nitrogen. 

 A first inspection of the diagram shows that superphosphate 



* The averages are practically identical with those of Table XL., 1876-1912. 



