166 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



Tlio following is tlio summary and conclusions which they have just 

 published in ii long article on " Some points in the composition of soils," 

 in the June number of the Journal of the Chemical Society for this year, 

 p. 420 : 



(1) The annual yield of nitrogen per acre in various crops, grown for many years 

 in succession on the eamo land without nitrogenous manure, Avas found to ije" very 

 much greater than the amount of combined nitrogen annually coming down in rain 

 and the minor measural)le aqueous deposits. 



(2) So far as the evidence at command euuLles us to judge, other supplies of com- 

 bined nitrogen from the atmosphere, either to the soil or to the plant itself, are quite 

 inadequate to make up the deticienoy. 



(3) The experimental evidence as to whether plants assimilate the free nitrogen of 

 the atmosi^here is very conflicting ; but the balance is decidedly against the supposi- 

 tion that they so derive any portion of their nitrogen. 



(4) When crops are grown year after year on the same land, for many years in suc- 

 cession without nitrogenous manure, both the amount of produce per acre and the 

 amount of nitrogen in it, decline in a very marked degree. This is the case even 

 when a full mineral manure is applied, and it is the case not only with cereals and 

 with root crops, but also with Leguminoscs. 



(5) Determinations of nitrogen in the soils show that, coincideutally with the de- 

 cline in the annual yield of nitrogen i^er acre of these very various descriptions of plants, 

 grown without nitrogenous manure, there is also a decline in the stock of nitrogen iu 

 the soil. Thus a soil source, of at any rate some, of the nitrogen of the crops is in- 

 dicated. Other evidence pointed in the same direction. 



(G) Determinations of the nitrogen as nitric acid, in soils of knov?n history as to 

 manuring and cropi)ing, and to a considerable depth, showed that the amount of nitro- 

 gen in the soil in that form was much less after the growth of a crop than under cor- 

 responding conditions without a crop. This was the case not only with the gramin- 

 eous but witli leguminous crops. It was hence concluded that nitrogen had been 

 taken up as nitric acid by the growing crops. 



(7) In the case of gramineous crop soils, the evidence pointed to the conclusion that 

 most, if not the whole, of the nitrogen of the crops was taken up as nitric acid from 

 the soil. 



(8) In the experiments with leguminous croj) soils, it was clear that some at any 

 rate of the nitrogen had been taken up as nitric acid. In some cases the evidence was 

 in favor of the supposition that the whole of the nitrogen had been so taken up. Iu 

 others this seemed doubtful, 



(9) Although in the growth of leguminoas crops year after year on the same land 

 without nitrogenous manure, the crop, the yield of "the nitrogen in it. and the total 

 nitrogen iu the surface soil greatly declined, yet, on the substitution of another plant 

 of the same family, with diJlereut root-habits and root-range, large crops, containing 

 large amounts of nitrogen, may be grown. Further, iu the case of the occasional 

 growth of a legumiuous crop, red clover for example, after a number of cereal and 

 other crops manured in the ordinary way, not only may there be a very large amount 

 of nitrogen iu the crop, presumably derived from the subsoil, but the surface soil be- 

 comes determinably richer in nitrogen, due to crop residue. 



(10) It was found that, under otherwise parallel conditions, there was very much 

 more nitrogen as nitric acid, iu soils and subsoils down to a depth of 108 inches, where 

 leguminous than where gramineous crops had grown. The results pointed to the con- 

 clusion that, under the iuliuence of leguminous growth and croii-residue, the comli- 

 tious were more favorable for the development of the nitrifying organism and, espe- 

 cially in the case of deep-rooting plants, of their distribution, thus favoring the nitri- 

 fication of the nitrogen of the subsoil, which so becomes a soiirco of the nitrogeu of 

 such crops. 



(11) An alternative was that the plants might take up at any rate part of the nitro- 

 gen from the soil and subsoil us organic nitrogen. Direct experimental evidence loads 

 to the conclusion that fungi take up both organic nitrogen and organic carliou, but 

 there is at present no direct experimental evidence in favor of the view that green- 

 leaved plants take up either nitrogen or carbon in that form from llio soil; while 

 there aro physiological considerations which seem to luilitate against such a view. 



(12) In the cast; of pilots where TrifoUum repetia [white clover] and llcia salica 

 [tares or vetches] had been sown, each for several years in succession, on soil lo 

 which no nitrogenous manure had been applied for thirty years, and the surface soil 

 had become very poor in nitrogen, both the soil andaub.soil contained much less nitro- 

 gen as nitric acid where good crops of Fityia Haiiva had grown than where the more 

 shallow-rooted Tr\foliu>n repena had failed to grow ; and the deficiency of nitric nitro- 

 gen in the soils and subsoils of the Vicia aativa plots, compared with the amount iu 



