RELATION OF YIELD TO NITROGEN SUPPLY 101 



of crop is somewhat dependent on the source of nitrogen 

 employed : thus 1 Ib. of nitrogen as ammonium-salts gives an 

 increase of 0'130 ton, as nitrate of soda the increase is 0143 

 ton for each Ib. of nitrogen, while with rape cake the increase 



WITH COMPLETE MINERALS. 

 (PLOTS 4.) 



WITH DUNG. 

 (PLOTS 1.) 



Series 



N 



AC 



FIG. 14. Mangolds. Effect of increasing amounts of Nitrogen. Average 

 Produce of Roots per acre, 1876-1902. 



O = No Nitrogenous Manure. 



A = 86 Ib. Nitrogen as Ammonium-salts. 



N = 86 Ib. Nitrogen as Nitrate of Soda. 

 C = 98 Ib. Nitrogen as Rape Cake. 



AC = 98 Ib. Nitrogen as Rape Cake, and 86 Ib. Nitrogen as Ammonium-salts. 



is 0197 ton for each Ib. of nitrogen applied. Eape cake, in fact, 

 is not strictly comparable with the other two sources of 

 nitrogen, for not only does it contribute a considerable amount 

 of organic matter to the soil, thus improving its texture and 

 water-retaining power, but it is also a more slowly-acting 

 manure. Some of its residues accumulate from season to 

 season, and little by little become available for the later crops, 

 while we have plenty of evidence that, on the Rothamsted soil, 



