3<^0 



THE FARMER'S MAGAZINE. 



very various kinds, the conclusion has been arrived at, 

 that full crops of barley cannot be grown unless there 

 be, by some moaus, available nitrogen provided within 

 the soil. In practice it is frequently convenient to in- 

 crease the produce of the barley crop by the direct 

 application of i)ortable nitrogenous manures. It is very 

 desirable, therefore, both in a practical and scientific 

 point of view, to have some means of judging what is 

 the probable proportion of the nitrogen so supplied in 

 manure which will, on the average, or under given cir- 

 cumstances, be recovered in the immediate or successive 

 increase of crop obtained. The experimental evidence 

 which has been collected bearing upon this point also 

 throws some light upon the influence of season and 

 manuring on the per-centage of nitrogen in the barley 

 crop, and upon the amount of nitrogen obtained an- 

 nually from a given area without manure. 



Before speaking of the direct evidence which analysis 

 has supplied in the case of the experiments on the 

 growth of barley without and with nitrogenous manures, 

 the evidence and reasoning of others as to the proportion 

 of the nitrogen supplied in manure, which is recovered 

 in the increase of produce obtained by its use, may be 

 first briefly noticed. In his paper in the Journal of the 

 Royal Agricultural Society of England, before referred 

 to (vol. xvii. part 1), Baron Liebig deduces from Kuhl- 

 mann's experiments on hay, that when ammoniacal salts 

 were used alone, there was an apparent loss of four- 

 fifths or three-fourths of the nitrogen employed ; but 

 that, when mineral constituents were also added, there 

 was no such loss, but a gain from natural sources. To 

 show this gain, the instance is quoted in which Kuhl- 

 mann used about fifteen parts of nitrogen to a given 

 area in the form of guano. Adopting the same mode of 

 calculation, however, there would be a deficiency, in- 

 stead of a gain of nitrogen in the increase of produce, 

 where Kuhlmann applied it in the form of the very same 

 guano, but in just double the quantity to a given area, 

 as in the former instance. In another of Kuhlmann's 

 experiments, too, where a still larger proportion of 

 nitrogen was employed to a given area of land in the 

 form of sal-ammoniac, but mixed with phosphates, 

 there would be, still adopting Baron Liebig's mode of 

 calculation, a loss of more than 56 per cent, of the sup- 

 plied nitrogen. In fact, so far as the evidence and argu- 

 ments adduced bore upon the question, it appeared that 

 to attain the result of no deficiency of the supplied 

 nitrogen in the increase, but a gain over that supplied 

 in the manure, the farmer must employ it in quantity 

 which, in a practical point of view, was quite insignifi- 

 cant. The real bearing of the evidence which Kuhlmann's 

 experiments supply is not the question here. It is, too, 

 hardly necessary to reiterate an assent as to the essen- 

 tialness of a liberal supply of the necessary mineral con- 

 stituents of our crops. It has been frequently shown in 

 former papers, what, under an ordinary course of prac- 

 tical agriculture, with rotation, as it is, are the usual 

 circumstances of the removal and return of the mineral 

 constituents, and what the requirements for their direct 

 supply. 



The experiments of Kuhlmann above alluded to were 

 made upon grass. The direct results to be now noticed 

 have reference, as already intimated, to the experiments 

 in which barley was grown for six consecutive years on 

 the same land, by different manures, of which the same 

 description was applied to the same plot throughout the 

 six seasons. More than one hundred nitrogen determi- 

 nations were made on the barley corn or straw, grown 

 respectively with and without nitrogenous manures. 



Referring briefly to the influence of varying season 

 and manuring, upon the per-centage of nitrogen in the 

 produce of barley, it appeared from the results of the 

 few seasons over which the experiments extended, that. 



so far as the crops grown without nitrogenous manure 

 were concerned (that is, those which ripened best), the 

 tendency was to give the lower per-centage of nitrogen, 

 the higher the character of the crop, and vice versa. 

 The same has been found to be the case with wheat ; 

 but, as with the latter, so with barley, the rule is not 

 without exception ; it seems only to apply, on the ave- 

 rage, as our seasons go. 



When comparing the produce of the different seasons, 

 grown by nitrogenous manure, the rule just indicated 

 is not 80 clearly borne out ; but, as the influence of 

 even tiie smaller amounts of the nitrogenous manures 

 which were employed, was to produce over-luxuriance, 

 and depreciate the proportion and the quality of the 

 grain, that is, to be unfavourable to perfect maturation, 

 the apparent exception was rather a confirmation of the 

 assumption, that high maturation and low per-centage 

 of nitrogen were generally, with the average of our sea- 

 sons, coincident. 



" That we should get the higher qualities of crop in- 

 dicated with the lowest amounts of produce per acre, is 

 perfectly cousistent with the practically admitted fact, 

 that the sample, particularly of barley, is, on the ave- 

 rage, the better the smaller the amount of crop. This 

 smaller amount of crop is coincident with the relative 

 deficiency of available nitrogen within the soil ; and, 

 with this higher quality of sample obtained with a low 

 relative provision of nitrogen in the soil, we have a ten- 

 dency to low per-centage of nitrogen in the most 

 valuable descriptions of the grain. But quality cannot 

 in practice be bought at so great a sacrifice of quantity. 

 And it is seen that, when we increase the quantity of 

 crop by increasing the relative amount of available 

 nitrogen in the soil, it is generally depreciated in the ad- 

 mitted characters of quality ; and at the same time the 

 per-centage of nitrogen is increased. Further, the ten- 

 dency to diminished quality and increased per-centage of 

 nitrogen on the one hand, with increased amount of crop 

 on the other, would appear to be the greater, the more 

 excessive the supply of nitrogen beyond that which in 

 the average of seasons can yield a well-conditioned and 

 healthily-ripened crop. Barley indeed, from its com- 

 paratively limited hold on the soil, and its small and 

 weakly straw in proportion to the weight of corn it has 

 to carry, is, so far as favourable ripening and good 

 sample are concerned, more sensitive to vicissitudes of 

 season and to high manuring than wheat ; and it is with 

 the greater variation in degree of maturation in the 

 former than in the latter, in one and the same season, 

 with different proportions of available nitrogen provided 

 within the soil, that we have, at the same time, a greater 

 variation in the per-centage of nitrogen in the produce 

 depending on the manure employed." It would appear, 

 too, that we cannot, keeping within the limit of healthily- 

 matured full crops, increase the per-centage of nitrogen 

 in our barley grain much above a comparatively low 

 amount, as our seasons go. 



_ The next point of interest is, as to the amount of 

 nitrogen annually taken from the land in the produce, 

 where none was supplied in manure. " The highest 

 amount of nitrogen thus stored up from the unaided 

 soil and season lesources was in 1854 — namely, 32ilbs. 

 per acre ; the lowest amount was 17ilbs., in 1856 ; and 

 the average annual yield, taking the mean of the six 

 years, was about 28ilbs. It may be mentioned, that this 

 latter amount is more than that annually deposited in 

 rain and other aqueous depositions, in the forms of am- 

 monia and nitric acid. Investigation — of which there 

 is at the present time much going on in reference to this 

 subject — has still to determine the source or sources of 

 this annual excess of assimilated nitrogen, beyond that 

 supplied in the combined form, in the measured and 

 analyzed aqueous depositions. Whether it be due to 



