EFFECT OF EXCESS OF NITKOGEN 103 



Uromyces belce, and to a Torula, which is abundantly developed 

 on the mangolds on the plots receiving an excess of nitrogen 

 but is not present elsewhere in the field. 



Thus, towards the end of October the plots receiving the 

 excess of nitrogen present a very unhealthy appearance; a 

 large proportion of the plants seem scorched and withered as 

 regards the outer leaves, and only show a cluster of small dark 

 green active leaves at the heart. 



The above appearances are not confined to the plots 

 receiving very large amounts of nitrogen ; it is rather a 

 question of the relative excess of nitrogen as compared with 

 the quantity of available alkalies, especially of potash. Thus 

 the plants on Plot 1 AC are particularly bad, as they receive 

 the maximum amount of active nitrogen in addition to the 

 dung, whereas the plants on Plot 2 AC, which receive the 

 same nitrogen but also sulphate of potash, are comparatively 

 healthy. The plants receiving nitrate of soda as a source of 

 nitrogen show less damage than those receiving an equivalent 

 amount of nitrogen in the shape of ammonium-salts. Super- 

 phosphate, in the absence of alkaline salts, seems to increase 

 rather than diminish the injurious effects. 



B. Effect of Mineral Manures. The effect of the different 

 mineral constituents of a manure upon the mangold crop can 

 be seen by an examination of the results yielded by Plots 4, 

 5, and 6. Plots 5 receive superphosphate only at the rate of 

 392 Ib. per acre, Plots 6 receive 500 Ib. per acre of sulphate 

 of potash in addition to the superphosphate, while on Plots 4 

 the other alkalies which are taken up by the plant are added 

 in the shape of 200 Ib. of sulphate of magnesia and 200 Ib. of 

 common salt per acre. In the cross-dressings of nitrogenous 

 manures it should be noticed that all the plots in Series N 

 receive soda through the use of nitrate of soda, whereas the 

 other nitrogenous dressings, being either ammonium-salts or 

 rape cake, provide no appreciable amount of alkaline salts. 



Table XL. gives the results to 1912, and the following 

 diagram (15) shows these results set out in a graphic form, for 



