STIMULATING INFLUEI^CE OF NITHIC ACID AND OF AMMONIA. 167 



We have seen that the quantity of nitrogen contained in a crop raised 

 by the aid of farm-yard manure, is very much greater than that which 

 exists in the manure itself, and the views just exposed serve to indicate 

 the sources from which the excess is derived. But suppose that upon 

 two patches of ground, of equal quality, the one of which is manured 

 and the other not, equal quantities of the same seed be sown, it is 

 consistent with experience — that the crop reaped from the manured 

 poftion will not only contain more nitrogen than that reaped from the 

 unmanured portion, but so much more as shall considerably exceed that 

 contained in the manure itself. Thus suppose the crop raised from the 

 unmanured land to contain lOOlbs. of nitrogen, and that the manure laid 

 on the other portion contained 100 lbs. also, the crop which is reaped 

 from this latter portion, in favourable seasons, will exceed, and probably 

 very far exceed, 200 lbs. Hence the effect of the ammonia, &;c., in the 

 farm-yard manure, is not merely to yield its own nitrogen to the plant, 

 but to enable it, in some way hitherto unexplained, to draw from other 

 sources a larger portion of the same element than it would otherwise do. 

 So also with the nitrates. If two equal portions of the same grass or 

 corn-field, in early spring, be measured off, and one of them be top- 

 dressed with nitrate of soda or with saltpetre, the weight of nitrogen con- 

 tained in the crop of hay or corn reaped from the latter, will generally 

 be found to exceed that contained in the crop from the former, by a 

 quantity much greater than that which was present in the nitrate with 

 which the land was dressed.* In addition, therefore, to the nitrogen di- 



• The following calculations illustrate the statement in the text:— Mr. Gray, of Dilston, 

 [see Journal of Royal English Agricultural Society,] applied nitrate of soda to grjiss land in 

 the proportion of 112 lbs. to the acre. 



The produce without nitrate amounted to 2 tons 81 stones 

 with 112 lbs. of nitrate to 3 tons 146 stones 



Increase, 1 ton 65 stones, or 3150 lbs. 

 And 3150 -i- 112 = 28X lbs. the increase of hay from each pound of nitrate of soda. *^ But al- 

 lowing this hay to contain only one per cent, of nitrogen, 28 lbs. will contain i}4 ounces of ni- 

 trogen, which is nearly double the quantity actually present in the nitrate employed. 



Again, in the case of a crop of grain — Mr. Hyett applied nitrate of soda to a field of wheat, 

 and compared the produce with that from an equal p Ttion to which no top-dressing was 

 applied. 



CORN. STRAW. 



Bush. pks. pts. Cwt. qrs. lbs. 



Nitrated 43 2 11 31 2 3 



Without nitrate . . 33 2 6 23 1 21 



Excess, 10 5 8 10 



Calculating the bushel of com at 60 lbs., the excess of t ">rn amounted to 600 lbs., containing 

 24>4' per cent, or 147 lbs. of gluten and albumen. The nitrogen in these substances, when 

 properly dried, is from 15 to 17 per cent. If we suppose the gluten not to have been quite 

 dry, and allow only 14 per cent, of nitrogen, 147 lbs. would contain 20X lbs. of this element. 

 But the nitrated corn contained 5 per cent, more gluten and albumen than the un-nitrated, 

 which in 33 bushels (2000 lbs.) gives 100 lbs. of gluten in excess, containing 14 lbs. of nitrogen. 

 And 8 cwt. ofstraw(900 lbs.) contained one-third of aper cent, of nitrogen, [Boussingault,] 

 or in all 3 lbs. 



Therefore the quantity of nitrogen present in the nitrated crop above that in the un-nitrated 

 was as follows : 



1°. In 600 lbs of wheat at 24)^ percent, of gluten 20X lbs. Nitrogen. 



2°. In20001bs. of wheat at 5 percent, of gluten contained in excess, 14 lbs. do. 

 3°. In 900 lbs. of straw at one-third per cent 3 lbs. do. 



Total nitrogen =37^ lbs. 



But the nitrogen in 1 cwt. of dry nitrate of soda, as already stated, is only 19 lbs. or little 



[' Dry nitrate of soda contains about J6>^ per cent, of nitrogen, being 19 lbs. to the cwt., 



or two and three-fifth ounces to the pound ; but as it is usually applied, it contains from 5 to 



10 per cent, of water. The nitrogen, therefore, may be estimated at 2}i ounces in the poimd. ] 



