NITRATE OF SODA AND AMMOM r M S A ITS i(»7 



remaining tufts of small loaves, which show no >iLMi> of 

 completing their growth however prolonged the si'ason may he. 



C. Comparison of Nitrate of Soda and Amman} nw-.oilt.-' as 

 sources of Nitrogen. It has already been pointed out that the 

 plots of Series N cross-dressed with nitrate of soda, give 

 better crops than the corresponding plots of Series A. whicli 

 receive the same amount of nitrogen in the form of ammonium 

 sulphate and chloride. This is particularly the case on Plots 

 5 and 8, w^here no potash is added, for the soda of the nitrate 

 of soda seems to supply the alkali needed by the plant, or at 

 any rate enables it to utilise the reserves contained in the 

 soil. The superiority of nitrate of soda is, however, also Ncry 

 evident on the other plots receiving potash or the comijlete 

 alkaline salts. Taking the mean of Plots 1, 2, 4, 6, and 7. and 

 comparing Series N and A, the crop obtained with 80 11 >. of 

 nitrogen in the form of nitrate of soda exceeds the crop of the 

 corresponding plots in the ratio of 100 to 89. On the 

 Rothamsted soil nitrate of soda always gives rather a higher 

 return than ammonium-salts, but not quite to the same extent 

 with other crops as with mangels ; the superiority of nitrate 

 of soda is, however, not so marked as to suggest any specific 

 affinity of mangels for nitrate of soda, lovers of saline matter 

 and of nitrates though they are. 



The cause of the superiority of the nitrate of s(j(la is 

 probably to be found in the different character of the growth it 

 induces ; being freely soluble in water and not retained in any 

 way by the soil, it sinks more readily, with the result that the 

 plant develops a longer and deeper root-system to follow the 

 nutriment. Ammonium-salts, on the contrary, are immediately 

 absorbed by soil of the Kothamsted type, and are retained 

 very close to the smface ; the plant in consequence deveIoj)s a 

 root-system correspondingly near the surface, and does not 

 search the subsoil so thoroughly for either food or water. 



The appearance of the mangel cnjp when it is ready to lift 

 also confirms the opinion expressed al)ove, that the superiority 

 of the nitrate of soda is partly due to the increased I'oot -range 



