22 



CULINARY OR KITCHEN GARDEN. 



leaves are constantly absorbing carbonic 

 acid from the air, and giving off oxygen 

 gas ; that is to say, they are continually 

 appropriating carbon from the air. When 

 night comes this process is reversed, and 

 they begin to absorb oxygen, and give off 

 carbonic acid. But the latter process 

 does not go on so rapidly as the former j 

 so that, on the whole, plants when grow- 

 ing gain a large portion of carbon from 

 the air. The actual quantity, however, 

 varies with the season, with the chmate, 

 and with the kind of plant. The propor- 

 tion of its carbon which has been derived 

 from the air is greatly modified, also, by 

 the quality of the soil in which the plant 

 grows, and by the comparative abundance 

 of liquid food which happens to be within 

 reach of its roots. It has been ascertained, 

 however, that in our climate, on an ave- 

 rage, not less than from one-third to four- 

 fifths of the entire quantity of carbon 

 contained in the crops we reap from land 

 of average fertility is really obtained from 

 the air." — J. F. W. Johnston, in Agricul- 

 tural Chemistry and Geology, p. 40. And 

 without quoting other authorities — of 

 which there are many — we refer to the 

 recent experiments made by M. Barral, 

 given above, in which he shows that 227 

 lb. of the six elements of fertilisation are 

 returned to the soil, per acre, per annum, 

 by the rains which fall alone ; while ac- 

 cording to data, given above, by agricul- 

 tural chemists, 76.22 lb. are all that is 

 required per acre to re-establish the soil 

 to its former condition, after a crop of 

 wheat has been taken from it, so far as 

 these mineral ingredients are concerned. 

 Nitrogen is required in great abundance 

 in most plants, in some more than in 

 others ; and to obtain this from the 

 atmosphere, the agency of saline sub- 

 stances may be necessary; for of such 

 importance is their influence in this re- 

 spect, that crops have been grown on soils 

 destitute of organic matter, but contain- 

 ing saline substances, which procured 

 sufficient nitrogen from the atmosphere 

 to cause the plants to flower, fruit, and 

 yield ripe seed, notwithstanding they 

 were only supplied with distilled water, 

 which, of course, could convey to the 

 plants none of those fertilising elements 

 discovered by M. Barral in rain-water. 

 Mr Stephens, in summing up the evidence 

 he has so carefully collected, concludes 



by observing, in " Book of the Farm," vol. 

 ii. p. 456 — " Upon the whole subject of 

 special manures, the rationale of their 

 application may be based upon the cer- 

 tainty of the fact, that a large produce 

 will be obtained, if we only return to the 

 soil the mineral constituents of the crops 

 we cultivate, in combination with nitro- 

 genous substances, and the materials 

 should be in a state to become fit for 

 assimilation by plants." We are far from 

 despising the use of special manures, but 

 we would employ them as auxiliaries 

 only, and advise the cultivator to con- 

 sider as his sheet-anchor the contents 

 of a well-managed dung-yard, which 

 contain nitrogen in great abundance, 

 which is known to excite the growth of 

 vegetables, and also to render their pro- 

 ducts more valuable as food for man. It 

 also contains much carbon, which, enter- 

 ing into their structure, imparts to 

 them firmness of texture, and strength 

 to maintain themselves in an upright 

 position — the only position in which they 

 could be placed, to derive the necessary 

 advantages of atmospheric influence. 



We look upon mineral or special 

 manures, applied as restoratives in the 

 routine of rotation, in the light of make- 

 shifts ; and whilst we admit their great 

 value in agriculture, where, as things are 

 managed, a sufficient quantity of stable- 

 yard manure cannot or is not to be had — 

 and also their importance in elevated 

 situations, to which it would be too ex- 

 pensive to transport it — still we would 

 not have cultivators to place their depen- 

 dence on them alone. Besides, there is 

 more than mere mauurial applications 

 required. The soil must be prepared for 

 their reception, so that the process of 

 free and copious evaporation may go on ; 

 and this cannot be expected to be com- 

 pletely realised, unless that soil be wrought 

 to a considerable depth, and thoroughly 

 amalgamated with those additions, what- 

 ever they may be, to insure a gaseous 

 supply of food through the leaves, in 

 addition to what is absorbed by the roots. 

 Notwithstanding all this, and admitting 

 that one species of crop may be grown 

 for several continuous years on the same 

 ground, it is, nevertheless (whether the 

 cause rests in the exhaustion or excre- 

 mentitious theory), wrong to crop the 

 same ground, unless under peculiar cir- 



