79 
SCIENTIFIC SUMMARY. 
AGRICULTURE. 
rUIIE Accumulation of the Nitrogen of Manures in Soils . — A paper on this ex- 
A tremely important subject has been prepared by Messrs. Lawes and 
Gilbert, in wbicb the authors have described the various conditions favourable 
and unfavourable to the retention of nitrogen by the soil. The more striking 
general result of these researches was that, although a considerable amount of 
the nitrogen of the supplied manure which had not been recovered as increase 
of crop was shown to remain in the soil, still a larger amount was as yet 
unaccounted for. Initiative results indicated that some existed as nitric 
acid in the soil, but it was believed that the amount so existing would prove 
to be but small. In fact, it was concluded that a considerably larger portion 
would remain entirely unaccounted for in the soil than was there traceable, 
and the probability was that at any rate much of this had passed off into the 
drains, or into the lower strata of the soil. Finally, it was shown, by refer- 
ence to field results, that there was not more than one or two bushels of 
increase in the wheat crop per acre per annum due to the large accumulated 
residue of nitrogen in the soil, notwithstanding its amount was many times 
greater than that which would yield an increase of twenty bushels or more 
if applied afresh to soil otherwise in the same condition. On the other hand, 
it was shown that the effect of an accumulated residue of certain mineral 
constituents was not only very considerable in degree but very lasting. 
Effects of Irrigation with Development of Certain Plants . — In a series of 
papers in the Artisan on the effects of irrigation on plants, the following 
statements are made, and deserve attention. It is said that a marked effect of 
liberal sewage irrigation on the mixed herbage of grass land is greatly to de- 
velop the grasses, to diminish the Leguminosse, and to reduce the prevalence 
of miscellaneous or weedy plants, but much to encourage individual species. 
Among the grasses, according to locality or other circumstances, the rough 
meadow-grass ( Poa trivialis ), couch-grass ( Triticum repens), rough cock’s 
foot ( Dactylus glomerata), woolly soft grass (Ilolcus lanatus), and perennial 
rye-grass ( Lolium perenne ) have been observed to become very prominent ; 
two or three only remaining in any considerable proportion after some years 
of liberal sewage application. But sewaged produce being generally cut or 
grazed comparatively young, the tendency which the great luxuriance of a 
few very free-growing grasses has to give a coarse and stemmy later growth 
is not an objection, as in the case of meadows left for hay. — Vide The Ar- 
tisan, October, November, December, 186G. 
