TRANSACTIONS OF THE SECTIONS. 53 
illustrate, by reference to direct experiment, that which had been before only assumed, 
regarding the yickl of. nitrogen.in our different crops. To this end the annual pro- 
duce of nitrogen per acre had been determined, in the case of various crops, which 
were respectively grown for many years consecutively on the same land; namely, 
wheat, fourteen years; barley, six years; meadow hay, three years; clover, three 
years out of four; beans, eleven years; and turnips, eight years. In the majority of 
the instances referred to, the yield of nitrogen had been estimated, both for the crop 
grown without manure of any kind, and for that with purely mineral manure, that 
is, excluding any artificial supply of nitrogen. It was the object of the present com- 
munication to give a summary view of some of the facts thus brought to light. 
Beans and clover were shown to yield several times as much nitrogen per acre as 
wheat or barley. Yet the growth of the leguminous crops, carrying off so much ni- 
trogen as they did, was still one of the best preparations for the growth of wheat; 
whilst fallow (an important effect of which was the accumulation within the soil of the 
available nitrogen of two years into one), and adding nitrogenous manures, had each 
much the same effect in increasing the produce of the cereal crops. 
Other experimental results were adduced, which illustrated the fact, that four years 
of wheat, alternated with fallow, had given as much nitrogen in the eight years as 
eight crops of wheat grown consecutively. Again, four crops of wheat, grown in alter- 
nation with beans, had given nearly the same amount of nitrogen per acre as the four 
crops grown in alternation with fallow; consequently, also much about the same as 
the eight crops of wheat grown consecutively. In the case of the alternation with 
beans, therefore, the whole of the nitrogen obtained in the beans themselves, was over 
and above that which was obtained, during the same series of years, in wheat alone, 
—whether the latter was grown consecutively, or in alternation with fallow. 
Interesting questions arose, therefore, as to the varying sources, or powers of accu- 
mulation, of nitrogen, in the case of crops so characteristically differing from one an- 
other as those above referred to. 
It had been found that the leguminous crops, which yielded in their produce such 
a comparatively large amount of nitrogen over a given area of land, were not spe- 
cially benefited by the direct application of the more purely nitrogenous manures. 
The cereal crops, on the other hand, whose acreage yield of nitrogen under equal 
circumstances was comparatively so small, were very much increased by the use of 
direct nitrogenous manures, But it was found that, over a series of years, only about 
four-tenths of the nitrogen annually supplied in manure for wheat or barley (in the 
form of ammonia salts or nitrates), were recovered in the immediate increase of crop. 
Was any considerable proportion of the unrecovered amount drained away and lost? 
Was the supplied nitrogenous compound transformed in the soil, and nitrogen in 
some form evaporated? Did a portion remain in some fixed and unavailable state of 
combination in the soil? Was ammonia, or free nitrogen, given off during the growth 
of the plant? Or, how far was there an unfavourable distribution, and state of com- 
bination, within the soil, of the nitrogenous matters applied directly for the cereal 
crops,—those, such as the leguminous crops, which assimilated so much more, gather- 
ing with greater facility, and from different ranges of soil, and leaving a sufficient 
available nitrogenous residue within the range of collection of a succeeding cereal 
crop? These questions, among others, which their solution more or less involved, 
required further elucidation before some of the most prominent of agricultural facts 
could be satisfactorily explained. 
Comparing the amount of nitrogen yielded in the different crops, when grown 
without nitrogenous manure as above referred to, with the amount falling in the mea- 
sured aqueous deposits, as ammonia and nitric acid, it appeared, taking the average 
result of the analyses of three years’ rain, that all the crops yielded considerably more, 
and some very much more, than so came down to the soil. The same was the case 
when several of the crops had been grown in an ordinary rotation with one another, 
but without manure, through two or three successive courses. Was this observed 
excess of amount in the yield over that in the yet measured sources, at all materially 
due merely to the extraction by the crops, of nitrogenous compounds previously ac- 
cumulated within the soil? Was it probably attributable chiefly to the absorption of 
ammonia or nitric acid, from the air, by the plant itself, or by the soil? Was there 
any notable formation of ammonia or nitric acid, from the free nitrogen of the at- 
