June 1, 1904.] 
THE TROPICAL AGRICULTURIST. 
817 
slakis:g. 
Quicklime. Waler. Slaking lime. 
Oa02 H.0 = CaH202 
56 18 = 74 
RE CARBO.VATING. 
Slaked lime. Carbonic acid. Mid lime. Water. 
Cam 02 C02 —- CaCOi H2O 
As recaibonating goes on simultaneously wiili 
slaking when Quicklime is merely exposed to tbe 
air, slaked lime usually consists of a mixtuie of 
mild carbonate of lime and hydrate of lime, repre- 
sented by the formula, 
CaCOl CaH20'. 
Lime, either as carbonate or quicklime, has many 
uses in agriculture, its effect on soils being both 
mechanical atid chemical : it also acts to some 
extent as a plant food. 
THE FORM IN WHICH IT SHOULD BE EMPLOYED 
depends on both the physical and chemical com- 
position of the soil. For light, free, sandy soils 
poor in humus, carbonate of lime is preferable ; 
while for stiff clayey soils, or soils rich in organic 
matter with an undue amount of acidity, quick- 
lime is better. On free soils lime acts as a 
cementing material to bind the loose particles 
together, this effect bsing produced by the solution 
of the lime as bi-carboiiace in the soil water and 
its deposition over the particles, as the excess of 
carbonic acid holding it in solution, evaporates. 
On clay soils, however, it has a contrary effect, 
especially when applied as quicklime, which dis- 
solves in water to form an alkaline hydrate and 
which has the property of coagulating clayey 
particles and forming small aggregates of the finer 
particles, between which moisture and air can 
readily pass. On peaty soils, the lime immediately 
combines with any of the free humic acids, form- 
ing neutral humates and thus renders the soil 
more suitable for plant growth and bacterial 
development. 
ONE OF THE M03T IMPORTANT USES 07 LIME IN SOILS. 
is to supply a base iu connection with the nitri- 
fication of the reserve organic nitrogen in the 
soil, or of the various forms of organic nitrogen 
supplied in manure?. Tnis nitrification is brought 
about entirely through the agency of certain soil 
bacteria which require a neutral or slightly alka- 
line reaction in the surrounding soil. Most Ceylon 
tea soils are somewhat deficient in lime and con- 
sequently show a slightly acid reaction in which 
case nitrification can only take place slowly, if at 
all : consequently the necessity for an application 
of lime is indicated ; fir^t to neutralise the free 
humic acids in the soil, and secondly to supply a 
base to combine with and neutralise the nitrons 
and nitric acids as they are produced. It is in 
the form of nitrate of lime, which is a very soluble 
salt, that almost all the nitrogen required passes 
into the plant ; hence the necessity of lime in 
the soil, if continuous flushes are to be obtained, 
is obvious. Lime also acts as a base for the double 
decomposition which occurs when sulphates of 
ammonia or potash are applied to the soil — 
the lime combining with the sulphuric acid 
of the salts to form sulphate of lime, 
thus liberating the bases, ammonia and potash, 
which are retained by some of the constituents 
of the soil for the use of the plant. It also has 
a very marked effect on the liberation of the 
insoluble mineral constituents of the soil especially 
potash. This potash occurs in Ceylon soils iu com- 
bination as double silicates of alumina and potash 
and these are decomposed by the lime with the 
liberation of the potash. 
As lime itself supplies no additional food to the 
I Iml, but only sets in action the dormant constitn- 
ents of the soil, its continued application in large 
quantities without manuring would soon result in 
exhaustion of tl>e land, at least as ret^ardsita 
fairly easily available plant food. But the applica- 
tions recoran.ended in Ceylon, of 2 to 3 cwts per 
acre every second or third year after pruning, aie 
no- likely to do harm in this respect, especially 
as the additional food that would be liberated for 
the tea bu^h by its usejis more than replaced by 
the manuring that follows the liming process. In 
temperate climates the usual application of lime 
is from 2 to 4 tons per acre every 8 or 10 years, 
but in Ceylon heavier applications than * to 5 
cwts per acre are rarely necessary. As a rule lime 
has usually been 
APPLIED TO BURIED PRUNINGS TO HASTEN THEIR 
DECOMPOSITION 
and destroy any fungus growth ; but now broad- 
casting over the stems of the pruned bushes to 
destroy lichen, and over the surrounding soil, is 
becoming more general, as the lime is better 
distributed through the soil for nitrification pur- 
poses. Experiments in other countries have shown 
that where lime is used in conjunction with 
artificial manures, the effect of the latter is in- 
creased by 10 to 20 per cent. One drawback to the 
application of quicklime or slaked lime is its effect 
on the coolies' hands and feet, especially when 
the weather is wet; or the bushes damp with dew. 
A suitable hand-machine for broadcasting lime 
would be of much service. The effect of the lime 
on the skin can be minimised by rubbing with 
coconut oil after the day's work. 
Finely-ground Coral or stale slaked lime has the 
advantage over quicklime in that it does not 
injure the hand*:, but its slower action on most 
soils renders its use limited. It is also of no use. 
for broadc isting over the stems of bushes to destroy 
lichen and mosses, but on some very light soils poor 
in humus it might be employed with advantage. 
Ceylon Limestones or Dolomites— As men^ 
tioned before, these are mainly mixtures of 
carbonates of lime and magnesia with varying 
quantities of qarlz. As a rule they are not 
generally regarded as suitable for manurial purpo- 
ses, and in some cases they have proved injurious 
rather than beneficial, this being probably due to 
the magnesia present, as it has been found that 
many plants require a much larger proportion of 
lime in the soil than magnesia. For cocoa, however, 
which doey well in the soils containing a good 
proportion of dolomitic lime stone, its application 
might be of service. From numerous analyses of 
Ceylon soils that have been under cultivation for 
varying periods, it wouldappear that the available 
lime originally present in the virgin soils has more 
or less dissppeared, v.'I.ich is only to be expected 
as lime is the chief base removed in the drainage 
water. It is possible that this may losijme extent 
account for the loss in the quality of the tea, 
which is said to be taking place in Ceylon, and 
would be a farther argument in favour of an 
occasional application of lima to the soil. Analy- 
ses of the asii of tea leaves and pmuiiigs show that 
lime is present in considerable quantities, so that 
there is undoubted proof that a certain amount of/ 
it is necessary for healthy growth, and it is shown 
in practice by the healthy appearance of the 
bushes grown under grevilleas, which bring up large 
quantities of lime from the subsoil and leave it 
on the surface on the fall of their leaves. 
