104 



EXPERIMENTS UPON ROOT-CROPS 



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 super- 

 phosphate only ; the third, that of Plot 6, with potash in 



Ammonium Salts. 



□ NoMinerals. p^Superphosphate. IpSuperphosphate ■ Superphosph 



y^yj [^\2j and Potash. H Magnesia s 



ate. Potash, 

 and Soda. 



Fig. 15. — Mangel Wurzel. EiFect of variou.s Mineral Manures. 

 Produce of Roots per acre, 1876-1902. 



Average 



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 (O) 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 



