! 



686 



KEPORT — 1884. 



The total combined nitrogen brought to the earth annually in measured 

 nqueous deposits — snow, rain, Szc. — luis been found to bo only C'12 kilcs per 

 liiectare. 



An acid solution and a moist, acid, porous soil liave been found to absorb, for the 

 period of these experiments (seventy-two days in April, May, and June), combined 

 jiitrofron at tlie rate of some 10 kilos per hectare. The amount of nitropreu acfiuiiv(i 

 from the atmosphere in the one of these experiments, in wliich the conditions were 

 most nearly normal, was at the rate of in? kilos per hectare, twice as mucli as tlic 

 total nitrogen contained in grain i\ni straw of a wlu-at crop oi tliirty bushels, and 

 more than the total nitrogen of three tons of clover iiay. 



4. On some iioiitfs in the GnmpnsitinH- nf SoiJx, irifh results ilhistrnthh/ the 

 Somxes of Fertiliti/ of Mmnfoha Fr.airie Snih. By Sir John B. Lawe< 

 Bart., FJi.S., and Dr. J. H. GiMifEKT, F.E.S. 



This paptr was ontinuatiou of one given by the authors at the meeting of 

 (lit! American Association, lield at [Montreal two years previously, cntitlfd: 

 ' Determinations of nitrogen in the soils of some of the experimental fit-Ids at 

 liothamstt'd, and the Ijcaving of the results on the question of the sources of the 

 nitrogen of our crops.' The first part nf the present paper consisted of a resume 

 of the previous one. 



It was shown tluit when crojis were grown year after year on the same land 

 ■without nitrogenous manure, the produce, and the yield of nitrogen, declined in a 

 very marked degree. This was the ciise even wOuui a full mineral mmuiro was 

 applied; and it was the case not only with cort-als and with root-crops, but also 

 ■with Leguminoscc. Further, -with this great dt>cline in the annual yield of nitrogen 

 of these veiy various descriptions of ])lant, when gntwii without artificial nitrogenous 

 supply, there was also a marked decline in the stock of nitrogen in the soil. Thus a 

 soil-source, of at any rate some, of the nitrogen of the crops was indicated. Other 

 ■evidence was also adduced clearly pointing to the same conclusion. 



Next, determinations of the amounts of nitrogen as nitric acid, in soils of 

 known history as to manuring and cropping, ami to a considerable dejitli, showed 

 that the amount of nitrogen in the soil in that form was much less after the 

 grmvth of a crop than under corresponding conditions without a crop. It was 

 hence concluded that nitrogen had been taken up by the plant as nitric acid. In 

 the case of gramineous crops, and some others, the evidence pointed to the conclu- 

 sion that most, if not the whole, of the nitrogen was so taken up from the soil. It 

 was also clear that some, at any rate, of the nitrogen of Li'i/iimi'noHiv, liad the 

 same source, and the results were in favour of tlie supposition that in some of the 

 cases the whole of it might ))e so accounted for. iStill it was admitted that, in 

 some cases, this seemed very doubtful. 



The conditions and the results of a large numl)er of new experiments were 

 next described. It was found that there was very much more nitrogen as nitric 

 acid, in soils ami sub-soils, down to the depth of 108 inches, where leguniiuous 

 than where gramineous plants had grown. The results pointed to thi> cimclusion 

 that under tht^ influence of leguminous growth and crop-residue, especially in tiie 

 case of strong ami deep-rooted plants, the conditions were more fa\ourabie ftir the 

 development and distrilmtion of the nitrifying organism ; and, if this xiew were 

 confirmed, an important step would be gained towards the more comidete explana- 

 tion of the sources of the nitrogen of the Lci/niiiin is(r which assimilatti a verv larpe 

 quantity of lutroT-en, inducing, as above supjioseil, the nitrification of tin; nitrogen 

 of the su))Soil, which may thus become the sounnj of the nitrogen <)( .sneh crops. 

 An nlti'rnative obviously was, that the plants might still take up nitrogt^n from tiie 

 subsoil, but as organic nitrogen, and not as nitric acid. There was, however, no 

 direct expiM'imentnl eviilcnci! in favour of such a \iew. whilst some ])hysiologic'ai 

 consiih'ratioiis, wliicli were iliscussed, seiMiicil to lie against it. Ai;':iin, results 

 showed that the siiil ,nnd suhsoil contaiiit'ii less nitrogen as nitric acid MJ'ter the 

 growth of good crt)iis of /•/'•/'/ ■•^it/ini, than where the more shallow-i'ooted trifoliim 

 rcpeii'^ had faileil to grow. This was further evidence that tlie Lcr/uininoiics took up 



