May I, 1884.] 



THE TROPICAL AGRICULTURIST. 



799 



gether cease to be remunerative unless those constituents 

 of the soil which the crops have withdrawn from it be 

 replaced. The object of the agriculturist must therefore be, 

 so to work bis groimd that the soil never becomes exhausted; 

 but that he shall constantly obtain abundant crops, (t)ul ait 

 adeqi'ate interest on his capital^ the soil. 



There are two modes of securing this — (1) by a carefully 

 selected succession of different crops; and (2) by manures." 

 He must of course, in addition, depend (3) on a suitable 

 mechanical working, loosening, and ilraining of the ground. 



In consequence of the ^^ selective poir^r'' of plants^ a suc- 

 cession of a number of crops of alKahne plants causes the 

 soil to become for a time — and at length when all the al- 

 kalies have been consumed — unproductive for plants of this 

 description. But while the alkaline plant has the power of 

 drawing an unusual proportion of alkalies from the soil, it 

 leaves all the other nutrient substances comparatively un- 

 diminished. These substances, therefore, accumulate iu the 

 soil, the ^rnall consumption of them being outweighed by 

 the decomposing influence of the atmosphere, which is 

 constantly reducing to a soluble condition small quantities 

 of soil; and thus rendering their constituents available for 

 nutrition. The substances which are thus made available 

 for the i)lant, are retained hy fertile soils ; and thus their 

 solution by rain, kc, ensured, at least a suthcient time, 

 for the whole of the soil to become saturated by them. 

 It is therefore essential to good farming that the crop 

 of the "alkaUne plant" should be followed by one of 

 another kind, say a "siUceous" or grass-jjlant, and thus 

 a well chosen succes.siou of ditferent crops will remove from 

 the soil one substance after another. This is known as a 

 *' rotation of crops," and the rotation must be continued, 

 until the substances fii'st withdrawn are restored in such 

 proportion and distribution, that the same species of crop 

 may again be grown. 



In former times the influence of the atmosphere on the 

 soil was utilized by cultivating only a portion of the soil, 

 tpe rest being left unfilled, or in naked fallow; but it is 

 now admitted that this mode of agricultiu-e is not economical. 

 When agriculture is made to pay best, no considerable por- 

 tion of land is left fallow, but the object is by a go'i't 

 rotation of- crops to utilize as equally as possible, all the 

 constituents of the soil. Even under the best system of 

 agriculture however the soil must become gi'adually esliaust- 

 ed,and tiiis exhaustion must be artificially coiinteracted. This 

 purpose is effected by a scientific system of manuruig, by 

 which those substances are supplied to the soil of which 

 it has most need. According to circumstances the most 

 various organic and inorganic substances may be employed 

 as manures. If, for example, there is a deficiency of nitro- 

 genous substances, an addition of nitrates, guano aud 

 organic manure. The phi/sical changes on the constitution 

 of the soil, often so advantageous, or even indispensable 

 to vegetation, caused by the rotation of crops, and by manur- 

 ing, opens a field too wide to be entered in this connection. 

 In Sicily and Asia Minor, once the '•granary of Rome," in 

 Compania aud Spain, at one time so fruitful, in the valleys 

 of the Potomac, Rappahannock aud James rivers, we have 

 the most sad and instructi%'e examples of exhaustion of soils 

 once fertile. 



The nutrient substances taken up by plants are, however, 

 by no means adapted in the raw state to take part in 

 the construction of any vegetable structures: they must, 

 on the contrary, undergo important transformations, and 

 become changed into organic compomids, suitable for nutri- 

 tion, [thus carbon must combine with oxygen and hydrogen 

 to form cellulose, starch, sugar, he, and C. H. O. N. S., and 

 Phosphorus must combine in a way to form albumen], known 

 as proximate elements. The process by which these simple 

 elements are combined into proximate elements and tissue 

 elements of the plant is called " ussimilatiou." It is not 

 possible at present to follow step by step the process of 

 assimilation. It seems to depend upon the following forces 

 — (1) the evaporation of the water contained in the nutrient 

 sap by transpiration, (2) the decomposition of carbon 

 dioxide [CO, ] and the fixation of carbon; (3) the formation 

 of albuminoids which are essential for the production of 

 protoplasm and Chlorophyll, (1) the formation of the sub- 

 stances from which cellulose is produced, viz., starch, the 

 different kinds of sugar, oil, and inuline. The chief source 

 of the carbon required for building up the tissues of |)lants 

 is the decomposition of the carbon dioxide [OOj ], contained 



in the atmosphere by the leaves. Only those cells which 

 contain chlorophyll, and then only under the influence of 

 light, have the power of decomposing the carbon cho.vide 

 which they take up, and of producing organic compounds out 

 of its elements, and those of water, with ehmination of an 

 equal vohmie of oxygen. 



OrUy firing chlorophyll has the power of decomposing the 

 carbon dioxide, and in general both sides of the leaf take 

 part in the process, but with different energy. Light and 

 heat are absolutely necessary for it. A small deficiency of 

 heat may be compensated by more intense light, but there 

 are limits which cannot be passed. Plants which do not 

 contain chlorophyll have no power of decomposing carbon 

 dioxide and hence of assimilating They must therefore 

 obtain their nutriment from substances ah-eady assimilated, 

 and hence grow either on, or in animals or other plants as 

 parasites, and obtain their nutriment from them; or live 

 [as saprophytes] on organic substances actu^y undergoing 

 decomposition and absorb their organic constituents before 

 they are completely decomposed, [e.g. mushrooms]. As I 

 have said before the mode of formation of the albimainoids 

 is still unknown. — Jno. E. Paue. — Southern Planter. 



AGKICULTDEE ON THE CONTINENT OF EUROPE. 



{Special Lette)'.) 



Pabis, March 22nd. 



It is not more than a century since France had only one 

 kind of meadow, the natural, and only one way for rearing 

 stock, pasturage iu summer and hay in winter. Thanks 

 to the cultivation of artificial grasses and rotation of crops, 

 the power of the laud has been tripled. All abandoned 

 lands become natural meadow, and will continue indefiuit^^ly 

 so if not broken up. Ai-tificial meadow is laid down for 

 a fixed number of years, or one year even, and sown with 

 selected seeds. A natural meadow demands less care aud 

 exacts less capital than artificial grass land, but the pro- 

 duce wiU be less. Certain grasses would die out as the 

 mineral matters they preferred became less, aud other 

 species would in due coui'se succeed. In laying lands down 

 to meadow, not only the soil but the climate should be 

 studied. A moderate temperature and a fair dose of humid- 

 ity are requisite for the success of meadows. Where these 

 conditions do not exist, luceru and sainfoin may succeed. 

 As the condition of soil, climate and humidity vary, so 

 will the grasses or ttor;e ; there are species suited for high, 

 medium and low lands. For the higher, the grasses like 

 a pure bracing air ; aromatic plants will abound there, and 

 so sheep and goats will thrive ; for medium altitudes, the 

 land wUl be less dry, and the plants more abundant ; such 

 pasture is excellent for horses ; whUe the thirds, if not 

 marshy, will suit black cattle. In marshy land the yield 

 will be good, but the ipiality deficient. The best meadows 

 are situated iu valleys, below the arable soil ; they will thus 

 enjoy the drainage of such land, thereby acquiring food 

 and humidity. Of course land lying on the borders of 

 rivers and liable to be inundated must remain under grass. 



In meadow lands the aim is to extirpate bad grasses, 

 keep land clean, irrigate at the right season, and carry off 

 all superabundant water. Ourches says that ordinary mead- 

 ows contain forty-two specimens of forage plants ; of these, 

 seventeen are useful, the remainder worthless or injurious. 

 On elevated pasturages there are thu'ty-eight species of 

 grasses, of which only eight are useful ; in low meadows 

 twenty -five species, and but four useful. From experimcnfs 

 made in Bretagne, it results, that, in the case of natural 

 meadows, there would be on high lands three-fourths loss, 

 and in low meadows six-seventh's, if cattle refused to con- 

 sume all the grasses that were useless and injurious. 



For natural meadows study the grasses peculiar to (he 

 locality. It the laud be duty, break up and crop it for 

 a few years, aud then lay down, sowing after corn suit- 

 able seeds — not the sweepings of hay lofts ; caution ought 

 to be used respecting the introduction of new varieties, 

 chiefly because they are new, though they may be natural. 

 Endeavour to have grasses that will come into flower at 

 the same time. Not a few farmers allow the cattle to feed 

 down the afterneath of the first crop : it is better to allow 

 the laud to get firm. In winter long manure is spread on 

 the grass and scattered by a light harrow in spring. Mow 

 the first crop of grass before coming into flower; roU 



