40 



residues of the manure, and thus obtain a maximum result. 

 The annual application of 1,000 Ibs. of rape-cake per acre, 

 with superphosphate, has yielded on an average 40 bushels of 

 barley ; the cake supplied about 49 Ibs. of nitrogen. During 

 the same twenty years, the application of 275 Ibs. of nitrate 

 of soda, with superphosphate, has given an average pro- 

 duce of 42 J bushels ; the nitrate supplied about 43 Ibs. of 

 nitrogen. Approximately, therefore, the comparative value 

 of nitrogen in nitrate of soda and rape- cake for the production 

 of barley is as 100 to 83. 



As cake nitrifies rather slowly, there would be more loss 

 from autumn drainage on the cake plot than on the nitrate ; 

 the two manures should thus be more equal in effect when 

 applied to crops the growth of which extended into the 

 autumn months. This is actually the case, the Eothamsted 

 field experiments with mangel wurzel showing a still better 

 return from cake applied as manure. On an average of 

 twenty years, the annual application of 2,000 Ibs. of rape cake, 

 with manures supplying phosphates, potash, soda, and 

 magnesia, has produced 20 tons 4| cwts. of mangel roots ; 

 while 550 Ibs. of nitrate of soda, with the same manures 

 supplying ash constituents, have yielded 17 tons 11^ cwts. of 

 roots. The weights of these two crops are almost exactly in 

 the same proportion as the quantities of nitrogen which they 

 supply ; according to the figures, therefore, the nitrogen in 

 the two manures had very nearly the same value. We may 

 add, however, that in good seasons the nitrate gives generally 

 the larger crop, while in a dry summer the seed germinates 

 much better on the rape-cake plot. 



The trial of rape-cake at Woburn as a manure for wheat 

 and barley has lasted seven years, and the conditions of the 

 experiment have not been such as to enable the cake to yield 

 its most profitable return. The cake has been applied as a 

 top dressing to the wheat about the end of January, and to 

 the barley just after the corn is up. The dressing has been 

 a large one, supplying 82 Ibs. of nitrogen per acre. No pro- 

 vision has been made for the supply of ash constituents to the 

 crop. The results furnish a striking illustration of the poor 

 return yielded by organic manures under such conditions. 



In the wheat experiments the average crops during seven 



