520 Oil the Growth of Barley hj different Manures, ^'c. 



to the estimate already given at pp. 488-9, most probably average 

 below 5 per cent, of nitrogen. In the Table XVIII. the result is 

 given both on the assumption of the above amount as a maximum, 

 and of 4"1 per cent, as a minimum ; rather above the mean 

 between the two, would probably be very near the truth. It may 

 be stated, however, that with the smaller percentage of nitrogen in 

 the rape-cake, the 2000 lbs. of the manure employed per acre, 

 would supply the same amount of nitrogen as the 400 lbs. of ammo- 

 niacal salts, and the 550 lbs. of nitrate of soda, used by its side. 



In making the selection of the specimens of the produce to be 

 analysed, the question arose — whether the results would bear a 

 more general application it that of certain characteristic in- 

 dividual manures were taken? — or whether, omitting points of 

 minor distinction, it would be better to endeavour to get the 

 mean composition of the produce of %c]iole series of plots, for 

 each of the six years separately over which the experiments were 

 continued? After consideration of the advantages and disad- 

 vantages of either partial course, the latter was adopted. The 

 samples prepared for analysis were therefore as follows : — 



1st. For each of the six years separately, a mixture of equal 

 weights of the corn (and also the same of tlie straws), from each 

 of the plots without nitrogenous manure. These comprised 

 the uninanured plot, and those with respectively, the "Mixed 

 Alkalies," the superphosphate of lime, and the mixed alkalies 

 and superphosphate of lime together. The composition of these 

 mixed samples, fjroion icithout nitrogenous manure, is taken to 

 represent that of the produce yielded by the unaided soil and 

 season resources of nitrogen in the several years. 



2nd. For each year, a mixture of the produce (corn and straw 

 separately), of each of the four plots where 200 lbs. of ammoniacal 

 salts were employed per acre. Tliat is, where this amount of 

 ammoniacal salt was employed alone, or in addition to each of 

 the three mineral manure conditions above referred to. 



3rd. For each year, a mixture (corn and straw separately), from 

 each of the four plots, with the otherwise unmanured or the same 

 mineral manure conditions, where 400 lbs. of the ammoniacal 

 salts per acre were used. 



4th. For each year, a mixture (of corn and straw separately), 

 from the produce where, in addition to the four above-mentioned 

 standard non-nitrogenised conditions, 2000 lbs. per acre of rape- 

 cake were employed. 



5th. An equal mixture, for the five years together (corn and 

 straw separately), of the produce during five consecutive years, 

 by 275 lbs. of nitrate of soda per acre per annum. 



6th. An equal mixture, also for the five years together (corn 

 and straw separately), from the plots where double the amount, or 

 550 lbs. per acre per annum, of nitrate of soda were used. 



