24 



On Agricultural Chemistry. 



But to return to the Table (V.J ; — a glance will show that in 

 every season the produce was greatly increased by ammoniacal 

 salts only ; and in the last two years even, when the amount of 

 ammonia supplied was increased, so also was there a greater in- 

 crease of produce obtained than in previous years ; and this, not- 

 withstanding there had been taken from the land in the previous 

 rotation a heavy amount of minerals without return, and in the 

 first five experimental crops the minerals, both of corn and of 

 straw, of larger crops than are the average of the county under 

 the ordinary system of rotation and home manuring. 



The comparison afforded in Table VI. is very instructive. It 

 ^ives the results of Plot 10Z>, by the side of the unmanured plot. 

 The manuring of this Plot \0h was, it will be remembered, in 

 1844 precisely the same as that for Plot 10a, last under consi- 

 deration ; but in the succeeding years a different method of 

 treatment was adopted. In this case, instead of giving year after 

 year ammoniacal salts, these have been alternated with no manure, 

 with minerals alone, and with minerals combined with ammo- 

 niacal salts, in order to ascertain how far the characteristic result 

 of each of the conditions, thus successively provided, would in 

 each case be developed, independently of the immediately pre- 

 ceding supply. 



In the first year, the mineral manure gives less than one bushel 

 increase ; — in the second, am.moniacal salts give 8f bushels in- 

 crease ; — in the third season, after a heavy dressing by ammonia, 

 and a heavy produce, the cessation of manuring reduces the pro- 

 duce to a trifle below that of the unmanured plot ; — in the 

 fourth year, ammoniacal salt alone increases the produce by one 

 half; — in the fifth, a complex mineral manure, supplying nearly 

 every mineral constituent of the crop in excess, and this combined 

 with ammonia, gives an acreage produce even rather less than was 

 obtained in the previous year without the minerals, and the pro- 

 portion of increase over the unmanured plot is very little greater. 

 In the sixth season we have, with a larger supply of nitrogen than 

 usual, namely, with 200 lbs. of sulphate and 200 lbs. of muriate 

 of ammonia per acre, an increase of 13i bushels, or more than 

 two-thirds over the unmanured plot. And in the seventh and 

 last completed experimental season, this very heavy dressing of 

 nitrogen is succeeded by a very liberal supply of minerals, which 

 minerals however raise the produce only two bushels above the 

 yield of the unmanured plot. Nothing can be more striking and 

 conclusive than the evidence afforded by the fluctuations in the 

 produce of this Plot 10^, as showing that it would be much 

 nearer the truth to say that the crop has risen and fallen in 

 proportion to the diminution or increase of the ammonia supplied 

 to it in manure, than of the mineral substances, as would be 



