504 



THE FARMERS' REGISTER. 



vegetable matter of the soil no connexion with 

 the growth of the trees or herbage 1— does il yield 

 them no regular supplies of nourishment? Does 

 nature every where form a vegetable mould on 

 which her wild flowers may blossom and her 

 primeval Ibrests raise their lofty heads'? Has the 

 agricultural experience of all ages and of all 

 countries led the practical tarmer to imiiate nature 

 in preparing such a soill Does nature work in 

 vain?— is all this experience to be at once reject- 

 ed ? 



While we draw conclusions, legitimate in kind, 

 we must be cautious how, in degree, we extend 

 them beyond our premises. 



Theconsidcniion of one or two facts will show 

 that our general conclusion must either be modi- 

 fied or more cautiously expressed. 



Il is true that plants will, in certain circum- 

 stances, grow in a soil containing no sensible 

 quantity of organic matter— but it is also true, 

 generally, that they do not luxuriate or readily 

 ripen their seed in such a soil. 



his consistent with almost universal observa- 

 tion, that the same soil is more productive when 

 organic matter is present, than when it is wholly 

 absent. 



That if the crop be carried otf a field, less 

 organic matter is left in the soil than it contained 

 when the crop began to grow, and that by con- 

 stant cropping the soil is gradually exhausted of 

 orgnnic mailer. 



Now it must be granted that tillage alone, with- 

 out cropping, would gradually lessen the amount 

 of organic matter in the soil, by continually ex- 

 posing il to the air and hastening its decay and 

 resolution into gaseous substances, which escape 

 into the atmosphere. Bui two years' open fallow, 

 with constant stirring of the land, will not rob it 

 of vegetable matter so effectually as a year of 

 fallow succeeded by a crop ot wheat. Some of 

 the vegetable matter, therefore, which the soil 

 contained when the seed was sown, must be 

 carried off the field in the crop. 



The conclusion, therefore, seems to be reason- 

 able and legitimate, that the crop which we 

 remove from a field has not derived all its carbon 

 directly from the air — but has extracted a portion 

 of it immediately from the soil. It is to supply 

 this supposed loss, that the practical farmer finds 

 it necessary to restore to the land in the Ibrm o( 

 manure — among other substances — the carbon 

 also of which the straw or hay had robbed the 

 soil. 



But how is this reconcileable with our previous 

 conclusion, that the whole of the carbon is derived 

 li-ora the air? The difficulty is of easy solution. 



A seed germinates in a soil in which no vege- 

 table matter exists ; it sprouts vigorously, in- 

 creases then slowly, grows languidly at the ex- 

 pense of the air, and the plant dies stunted or 

 immature. But in dying it imparls vegetable 

 matter to the soil, on which the next seed thrives 

 better — drawing support not only li-om the air, 

 but by its roots Irom the soil also. The death of 

 this second plant enriches the soil further, and 

 thus, while each succeeding plant is partly nou- 

 rished by food from the earth, yet each, when it 

 ceases to live, imparts to the soil all the carbon 

 which during its life it has extracted from the air. 

 Let the quantity which each plant thus returns to 

 the soil, exceed what it has drawn from it by only 



one ten-thousandth of the whole, and — uniesa 

 other causes intervene — the vegetable matter in 

 the soil must increase. 



Thus vi'hile it is strictly true that the carbon 

 contained in all plants has been originally derived 

 from the air — it is noi irue that the whole of what 

 is contained in any one crop we raise, is diredly 

 derived Irom the atmosphere — the proponion it 

 draws from the soil is dependent upon nuaieroua 

 and varied circumstances. 



The history of vegetable growth, therefore — in 

 so far at least as the increase of the carbon ia 

 concerned — may be thus simply slated : — 



A plant grows partly at the expense of the soil, 

 and partly at that of the air. When it reaches 

 maturity, or when winter arrives, ii dies. The 

 dead vegetable matter decays, a part of it ia 

 resolved into gaseous matter and escapes into the 

 air, a part remains and is incorporated with the 

 soil. If that which remains be greater in quan- 

 tity than that which the plant in growing derived 

 from the soil, the vegetable matter will increase ; 

 if less, it will diminish. 



In warm climates the decay of dead vegetable 

 matter is more rapid, and therefore the portion 

 left in the soil will be less than in more temperate 

 regions — in oiher words, the vegetable matter in 

 the soil will increase less rapidly — it may not in- 

 crease at all. 



As we advance into colder countries, the decay 

 and disappearance of dead vegetable matter, in the 

 form of gaseous substances which escape into the 

 atmosphere, become more slow, till at length, 

 between the parallels of 40* and 45°, it begins to 

 accumulate in vast quantities in liivorahle situa- 

 tions, forming peat bogs ol greater or less extent. 

 While the living plant here, as in warm climates, 

 derives carbon both from the earth and from the 

 air, the dead plant, during its slow ami partial 

 decay, restores little to the atmosphere, and 

 therefore adds rapidly to the vegetable matter of 

 the soil. 



Again, in one and the same climate, the decay 

 of vegetable matter, and its conversion into 

 gaseous substances, is more rapid, in proportion 

 to the frequency with which it is disturbed or 

 exposed to the action of ihe sun and air. Hence 

 this decay may be comparatively slow in shady 

 woods and in fields covered by a thick sward of 

 grass ; and in such situations organic matter may 

 accumulate, while ii rapidly diminishes in an un- 

 covered soil, or in fields repeatedly ploughed and 

 subjected to frequent cropping.* 



Being thus fitted, by nature, to draw their 

 sustenance — now (rom the earth, now from the 

 air, and now from both, according as they can 

 most readily obtain it — plants are capable of 

 living, though rarely a robust life, at the 

 expense of either. The proportion of 'heir food 

 which they actually derive from each source, will 

 depend upon many circumstances, — on the nature 

 of the plant itself— on the period of its growth — 

 on the soil in which it is planted — on the abun- 

 dance of food presented to either extremity — on 

 the warmth and moisture of the climate — on the 

 duration and intensity of the sunshine, and other 



* In removing a crop we take away both wfiat 

 the plants have received from the earth and what 

 they have absorbed from the air — the materials, in 

 short intended by nature to restore the loss of vegeta- 

 ble matter arising from the natural decay. 



