156 



TALKS ON MANURES. 



though not entirely, consist, is transformed into gaseous carbonic 

 acid, and what remains behind, becomes richer in nitrogen and 

 mineral matters. A parallel case, showing the dissipation of car- 

 bonaceous matter, and the increase in the percentage of nitrogen 

 and mineral matter in what is left behind, is presented to us in 

 fresh and rotten dung ; in long or fresh dung, the percentage of 

 organic matter, consisting chiefly of very imperfectly decom- 

 posed straw, being larger, and that of nitrogen and mineral 

 matter smaller, than in well-rotted dung. 



" The roots from the field after clover-seed, it will be borne in 

 mind, were dug up in November, whilst those obtained from the 

 land twice mown, were dug up in September; the former, there- 

 fore, may be expected to be in a more advanced state of decay 

 than the latter, and richer in nitrogen. 



" In an acre of soil, after clover seed, we have : 



Lbs. 



Nitrogen in first six inches of soil 4,725 



Nitrogen in roots 51 i 



Nitrogen in second six inches of soil 3,350 



Total amount of nitrogen, per acre, in twelve inches of soil... .JtyjiSJI 



" Equal to ammonia, 9,867 Ibs. : or, in round numbers, 3 tons 

 and 12J cwts. of nitrogen per acre; equal to 4 tons 8 cwts. of 

 ammonia. 



" This is a very much larger amount of nitrogen than occurred in 

 the other soil, and shows plainly that the total amount of nitrogen 

 accumulates especially in the surface-soil, when clover is grown 

 for seed ; thus explaining intelligibly, as it appears to me, why 

 wheat, as stated by many practical men, succeeds better on land 

 where clover is grown for seed, than where it is mown for hay. 



"All the three layers of the soil, after clover-seed, are richer in 

 nitrogen than the same sections of the soil where the clover was 

 twice mown, as will be seen by the following comparative state- 

 ment of results : 



"This difference in the amount of accumulated nitrogen in 

 clover-land, appears still more strikingly on comparing the total 



