304 Agricultural Chemistry. 



1844 had yiekled a produce higher by 8684 lbs. than that of the 

 field manured with sulphate of ammonia alone, yielded, in 1846, 

 3592 lbs. of hay. The field manured with sulphate of ammonia 

 alone yielded, in 1846, 3726 lbs. of hay ; that is, 124: lbs. more than 

 the other. The same manures which in 1844 had produced an 

 enormous increase, and to which the unscientific and ignorant 

 farmer would certainly, on account of this result, have attributed 

 a preponderating value, lost, in 1846, their effect, although applied 

 in the same quantity, and in the same proportions, to the same 

 soil ; and they lost their effect in the subsequent years, in the 

 same degree as they had at first produced a favourable result. 

 The increased produce of the first year determined the diminished 

 produce in the second and third years.* 



We see from these facts that the effect of each individual 

 manure, or the produce obtained by it, is dependant on fixed 

 and immutable natural laws, which must not be disobeyed nor 

 neglected, if the farmer wishes to secure the continuance or dura- 

 tion of his crops. By the use of ammoniacal salts alone we can 

 increase the produce of a field in a given time, but not on the 

 whole. The quantity of corn and cattle which a given surface 

 can yield stands in a fixed relation of dependance, which can only 

 he modified in regard to the time over xohich the action extends, to 

 the sum of the mineral constituents which the soil contains, and 

 which it can yield to the plant. 



If Kuhlmann had continued his experiments for ten or fifteen 

 years, it is as certain as any mathematical truth is, that with all 

 his expenditure of manure (ammoniacal salts) he would not have 

 obtained in that time 1 cwt. of hay more than his meadow would 

 have yielded without any manure whatever. The effect of any 

 special manure, for one year, does not enable us to draw any con- 

 clusion as to its effect in a second year ; and if such a manure 

 should produce a favourable result during five successive years, 

 it is certain that it will not have the same effect during ten years. 



No one can rationally suppose that there exist, for the legumi- 



* "Thus we have shown, that after supplying to the soil twice or thrice as 

 much nitrogen as was obtained in the increase yielded, there was, in the succeeding 

 year, no increase whatever due to the nitrogen not recovered in the year of the 

 application ; or that such increase, if any, was not only exti-emely small, but that 

 it occurred only when the application of the previous year had been obviously 

 very excessive." — Journal, vol. xvi. p. 475. 



" The instances given in Table V. prove the fact that a moderate supply of 

 ammoniacal salts to the wheat-crop did not leave any efficient residue for the 

 succeeding season." — Ih. p. 478, 



According to Mr. Lawes, a moderate supply is from 224 lbs. to 336 lbs. of 

 ammoniacal salts. This is from three to five times as much as is required for the 

 increase in a crop of wheat, calculated on its percentage of nitrogen. In scientific 

 language, Mr. Lawes, instead of saying that the instances prove the fact, ought to 

 have said, " The instances given in Table V. show that there was, in the suc- 

 ceeding year, no increase whatever." 



