58o 



THE TROPICAL AGRICULTURIST. 



[February i, 1884. 



cecflingly simple manner. Trapa verbanensiSjDe Nota- 

 ris ; Ngai Camphor. — Theepecimea sent by Mr. Frater 

 is uot white, but greenisli grey, which may be due 

 to defective piiri(ication. I can, however, scarcely 

 (loulit that it is identical with Ngai camphor, of which 

 a .'specimen previously existed in the Kew Museum ; 

 this Hanbiiry attributes to Blumm hahamifera, DO. 

 It is interesting to notice that, according to Kurz 

 ('Forest Flora of British Burma,' vol. ii. pp.82, 83), 

 niiimea balsamifera is abundant ia onr Indian posses- 

 sions. He desoribea it as " an evergreen shrub, some- 

 time's growing out into a small tree." He further 

 remarks: — "A most common and tronblesome weed, 

 f re. ly spiinging up in d^'serted touugyas and savan- 

 nahs, along river-sides, &c. all over Burmah, up to 



.'.OOO feet elevation Yields camphor equal to the 



Chiiii'se one." 



DRAINAGE. 



It shews how rarely drainage is practised on In- 

 dian Tea Plantations, tbat an article lu the 'Tea 

 Gazette should comriience thus : — 



Draining is an operation, the less a plantation requires 

 tlif better. As has been justly rem.irked, the tea indus- 

 try must not be handicapped by expensive expedients 

 being necessary to the full developemeut of the plants. 

 Draiiiinij, or the reclaiming of land from too moist 

 a condition, is necessarily a tedious and expensive 

 «ork, requiring no small amount of engineering know- 

 ledge and capital. And that the results amply repay 

 the capital and skill applied to the carrying out of 

 such reclamation in densely populated countries, where 

 money is abundant and arable land scarce, cannot 

 be ddubted. But that tea should not be grown, 

 and will certaiuly uot pny under such circumstances, 

 is cqu;illy certain. 



However, it sometimes unhappily happens, that a 

 portioa of a garden has been planted on marshly 

 land, or in a situation exposed to inundations, either 

 from neighbouring streams or excess of rain water. In 

 such a case, rather than abandon the plot, or allow 

 the plants on it to sicken and die off, it may per- 

 haps he better to attempt some simple expedients to 

 correct thi» initial blunder. 



The conclusiou of the article runs thus :— - 



It -should never be forgotten, that stagnant wafer is 

 one of the dendlkst enemies of the tea plant. Its pr.-sence 

 is inv.iriably indicated by the yellow, stunted, de- 

 bilitated appearance of the bushes and the abnormal 

 abundance of seeds on^ -their branches. 



There is only one alternative to draining a jjlot of 

 tfea,' and that is abandoning it, for it will never give 

 a remunerative yield — even if it does not die out. 



The more an earth weighs, the greater is its power 

 of retaining heat. The darker its color, .and the 

 smaller its power of retaining water, the more quick- 

 ly and strongly will it be heated by the sun's rays. 



The greati^r the power of containing water, the 

 more has it in general the power also of absorbing 

 moisture when in a dry, ■ and oxygen when in a 

 damn, state from the atmosp'&ere. 



When endued with a high degree of consistency, 

 it is slow to become dry. 



The greater the power of containing water, and 

 the greater the consistency of a siil, the eolder and 

 wetter, of course, will that soil be, as well as the 

 stiffer to work, eithir in a wet or dry state. Cold- 

 ness in retentive soils is caused chiefly by the re- 

 moval of the wa*er of drainage by evaporation. That 

 the evaporation of water produces cold is well known : — 

 it cools wine ; in hot climates it produces ice. 



Humid soils are little benefited by summer heats, 

 because water, in a quiescent state, is one of the worst 

 conductors of heat with which we are acquainted. 

 Water warmed at the autfaoe transmits little or no 



heat. The small warmed portion expands, becomes 

 lighter than that below, and consequently retains its 

 position upon the surface, and transmits on heat un- 

 derneatli. When water is heated from helov), the 

 portion first subjected to the heat, rises to the surf- 

 ace, and every portion is successively subjected to 

 the heat, and rises, and each having lost some of 

 the heat at the surface, is in turn displaced. Con- 

 stant motinn is kept up, and a constant approxim- 

 ation to im equ:il tem^ 2r.ature in the whole body. 



Drainage elevates the temper.iture of the soil, be- 

 cause, by removing the water of draiu.age, it prevents 

 that constant evaporation by which the suiface heat 

 is lowered. 



But it also acts in another way ; m.auy experiments 

 have shown that in retentive soils, the temperature 

 two or three ftet below the surface of the w.ater- 

 table is, at no period of the year, higher thnt 46 ° 

 to 40 ° in agricultural Britain. Drains placed two 

 or three feet below the water-table, draw out water 

 of the temperature of 48 °. Every particle of water 

 which they withdrew at this temperature is replaced 

 by an equal bulk of air nt a higher, and frequently 

 at a much higher, temperature. The iiiarmth of the 

 air is carried doien into the earth. The temperature 

 of the soil, to the depth to which th^ water is re- 

 moved, is in course of constant assimilation to the 

 temperature of the air at the surface. 



Lavergne, in his " Kural Economy," says: — "Take 

 this flower-pot :— what is the meaning of this small 

 hole in the bottom ? to renew the water. And why 

 renew the water? because it gives life or death : life, 

 when it is made only to pass through the bed of 

 the earth, for it leaves with the soil its productive 

 principles, and renders soluble the natritive properties 

 destined to nourish the plant. Death, on the other 

 hand, when it remains in the pot, for it soon be- 

 comes putrid, and rots the roots, and also prevents 

 new and nutritive water from penetrating." The 

 theory of drainage is exactly described in thia figure. 

 — Indian Tea Oazeile. 



GEEEN MANURING. 



When land is continuously cropped without restor- 

 ation of the constituents of plants it becomes annually 

 less ftrtile, through the diminution of the substances 

 which enter into the composition of plants — those which 

 exist in forms suitable for absorption by the roots being 

 gradually exhausted; and althou^jh a much larger 

 quantity of the same mvterials exist in the soil, they 

 occur (says Maclvor) "in insoluble and unassimilable 

 conditions, in the form of undecomposed fragments of 

 various rocks, mica, felspar and others, and only be- 

 come useful as nutriment for plants when natu'al 

 agencies at work in the soil have rendered them soluble 

 and therefore available." In order, therefore, to iiti'ord 

 time for these agencies to aet to such an extent as 

 to reduce the insoluble into soluble substances that oan 

 be appropriated by plants, ayear'scroppingisiutermitted, 

 and the ground is rested under whst is termed a fallow, 

 being frequently stirred, the better to expose the 

 particles of soil to the action of meteoric and chemical 

 influences, whereby it is to some extent recuperated 

 and its productive powers restored. The air furnishes 

 ammonia and nitric acid, the two principal sourci s of 

 nitrogen, one of the principal constituents of a fertile 

 soil. It most not be supposed, however, that fallow*ing 

 is a substitute for manuie, for the mineral constituents 

 required by plants are not at all increased, but only 

 a portion of them rendered soluble, and therefore tiie 

 more completely that object is gained the sooner will 

 the land be deprived of them, and its approach to 

 barrenness accelerated. It thus becomes a ipie^tion 

 with the farmer what is the best method to pursue 

 under the circumstance of a gradually lessening yiolJ 



