THE SOUTHERN CULTIVATOR. 
83 
MR. FOOTE'S PRIZE ESSAY. 
[Concluded fjfom page 75 .} 
MARL. 
Marl being but a modification of lime, com- 
bined witti variable proportions of divers other 
substances, it may be observed, in general, that 
whatever principles are applicable to lime, (af- 
ter having been deprived of its causticity,) are 
applicable also to the use of luarl, so far as its 
9iature only is regarded. We shall, therelore, 
treat but very brieriy of this substance. Suffice 
it to say, that its value has been highly appreci- 
ated in Europe, and in those portions of our 
own country where it has been most extensive- 
ly employed, and that, wherever it is practicable, 
the strong probability is that the tanner wdll find 
his interest in making a thorough trial of it. 
The most common locality ot marl is low, 
wet swmmps. It is readily distinguished from 
other light soils by its light grey color when w'et, 
and its white, chalky appearance when dry. — 
Its Avhiteness, indeed, w'ill commonly indicate 
pretty nearly its comparative value; since both 
depend on the amount of lime it contains. A 
sure test, however, of the amount of lime pre- 
sent, W'ill be to app]}^ to it a ffiw drops of sharp 
vinegar, if the marl be worth employing as a 
manure, it^w’ill efieiwesce; i, e. small bubbles 
will appear, occasioned by the escape of gas. 
In applying marl to difierent kinds ol soil, 
particular reference sliould be had to tivo cir- 
cumstances: 1st. The amount of its calcareous 
matter. 2d. Its texture. If the proportion of 
its calcareous matter be large, the smaller w’ill 
be the quantity proper to be applied, and vice 
versa. Again, if the marl be of a strong adhe- 
sive texture, containing a large amount of clay, 
its application v/ili be most profitable on loose, 
siiicious soils; if on the other hand, it be ol a 
sandy or shelly character, strong loams and 
clays will be most benefitted by its reception. — 
The common mode of its application is to 
spread it evenly over the surface, and in case of 
cultivated crops never to turn it under till it has 
been thoroughly crumbled down by the action 
of the atmosphere. The reason of this practice 
is thus stated by Chaptai “It is necessary for 
earths, in order to po.ssess great fertilizing pow'- 
ers, to be saturated Avith all the principles which 
they can imbibe from the atmo.sphere. Thus 
those which, by the depth of their beds, haA'e 
been constantly secluded from the action ol the 
air, will require to be exposed to it a longer time 
before becoming fertile. The lime contained in 
marl, as it is taken from the bed, is nermr saturat- 
ed Avith carbonic acid,- but after being exposed 
to the air, it becomes at length saturated Avith 
the acid it receives from it, crumbles and elfer- 
yesees. The decomposition of marl may be 
hastene I by frequently turning it, so as to alloAV 
the air free access to the lime; and this method 
is generally practiced by those who employ 
marl as a manure.” — p. 44. 
The quantity applied per acre may vary, ac- 
cording to circumstances, from five to twenty- 
five or thirty wagon loads. For a full discus- 
sion of this subject, see Hitchcock’s Geology of 
Massachusetts, a copy of which has been lodged 
Avith the town clerk of eA'ery tOAAm in the Com- 
monwealth. 
GYPSOMj OR PLASTER. 
Piaster, first introduced into the United States 
from Paris by Dr. Franklin, has efiected the 
most important improAmment in agriculture per- 
haps that has eA'er been made. Extensive dis- 
tricts in this and other countries, have been ben- 
efitted by its introduction to an extent which, 
considering the comparatiA'ely small amount ol 
the substance employed is truly astonishing. In 
Germany, says Lampodius, one of her own ag- 
ricultural Avriters, “It may Avith certainty be 
stated, that by the use of gypsum, the produce 
of clover, and the consequent amount of live 
stock hatm been increased at least one third.'’ 
“There are, however, some tracts of country 
where the use of plaster has been attempted 
without success. But this arose from its being 
one of the original constituents of the soil, 
which derived no advantage from the addition 
ofancAV quantity. The existence of this salt 
naturally, in. those lands upon which plaster 
produced little or no eflfect, has been proved by 
analysis.” — Chaptal, p. 73. 
Much mystery has heretofore enveloped the 
modus operandi* of this manure; but before the 
light ol science the cloud is vanishing away. — 
Many hatm supposed its efficacy to arise from 
the specific food Avhich it furnished to certain 
plants, as to cloAmr, for instance, which seems 
especially benefitted by its application. But 
w'hen we consider that by the application of a 
handful, as it were, of this manure, upon an 
acre of good ground, the product is increased 
from a few hundreds to tons of grass, it is at 
once apparent that, on such a supposition, the 
cause is wholly inadequate to the effect. It was 
reserved for the gifted and honored Liebig to 
lilt the A'cii, and to produce a theory, not only 
plausible in itself, but fully su.stained in all its 
parts by the experience of praclical men. 
His theoiy is this; that the efficacy of plaster 
consists in its arresting, as it rises in exhala- 
tions from the soil, or descends in rain, dew or 
snoAV from the atmosphere, the ammonia Avhich 
is generated by the decay of animal matter and 
appropriating it to the use of the groAving crop. 
We Avill permit him to present his OAvn vieAvs, 
however, in a fcAv extracts from his Organic 
Chemistrj'. 
“Nitrogen exists in eA-ery part of the vegeta- 
ble structure.” — p. 88. “All animal,” [and A'e- 
getable] “bodies, during their decay, yield the 
nitrogen which they contain, to the atmosphere, 
in the form of ammonia.” — p. 72. “The evi- 
dent influence of gypsum depends only upon its 
fixing in the soil the ammonia ol the atmos- 
phere, Avhich AA'ould otheiAvise be A'olatiiized, 
Avith the Avater AA'hich evaporates.” — p. 75. “In 
order to fonn a conception of the effect of gyp- 
sum, it may be sufficient to remark, that IlO 
lbs. of burned gypsum fixes as much ammonia 
in the soil as G250 lbs. of horse’s urine Avould 
yield to iL” — p. 88, “II a field be streAved with 
gypsum, and then with putrified urine, or the 
draining of dung hills, all the carbonic of am- 
monia Avill be conA^erted into the sulphate, 
which Avill remain in the soil.” — p. 184. “If we 
strew the floors of our stables, from time to 
time, with common gypsu n, they will lose all 
their offensiv'e smell, and none of the ammonia 
Avhich forms can be lost, but will be retained in 
a condition serviceable as a manure.” — p. 185. 
“But this is not all. When we give a plant ni- 
ti ogen in considerable quantity, we enable it to 
attract with greater energ}’’ from the atmos- 
phere, the carbon which is necessar}" for its nu- 
trition.” — 138. Now “carbon enters into the 
composition of all plants.” — 3. So that, by 
streAv ing a field Avith gypsum, Ai'e enable plants 
to supply themseh'es from the atmosphere, not 
only Avith nitrogen, on which their most nutri- 
tious principles depenil, but also Avith carbon, 
the chief constituent of ail their frame work. 
This theory is confirmed by several circum- 
stances which haA’^e long attracted the attention 
of the obseiwing farmer. 
1. It has been obserA’ed that plaster acts Avith 
increased efficacy Avhen applied in connection 
Avith manures, or recently manured lands. The 
solution of the phenomena by our theory is easy 
and satisfactory. The ammonia, Avhich would 
otherAvise escape from the decomposing ma- 
nure into the atmosphere, is seized upon by the 
plaster, detained in the soil, and wholly con- 
verted to the use of the groAAung crop. 
2. It has been observed that plaster acts Avith 
greater poAver on soils Avhich have been recent- 
ly stirred, than on those Avhich have lain for a 
long time unmoved. Solution — By stirring the 
soil its porosity is increased; consequently it ab- 
sorbs more freely the dews that fall upon it — 
from which the plaster separates and hoards up 
in the soil, the rich deposits of the atmosphere. 
In proof ot the extent to Avhich the atmosphere 
is charged with fertilizing matters, Avhich the 
rains and dews are constantly depositing upon 
the surface of the earth, we AAdll here introduce 
the substance of a statement made to the Amer- 
icanjeditorol Liebig, by M-. E. Tults,of Charles- 
town. 
“Eight years since, about three quarters of an 
acre of land, situated on one side of a lane and 
on a declivity, were broken up. About the 
same time, the proprietor of a field on the oppo- 
site side of the lane, and above the land of Mr. 
T., commenced gardening on a large scale, and 
formed an immense bed of compost in the lane. 
This heap was made up of animal and A'egeta- 
ble matters, and from receiA'ing constani addi- 
tions is continually undergoing fermentation, 
and the gases and A'apors emanating from it are 
always perceptible. Four years ago r,Ir. -T. 
observed, that in some inexplicable Avay, his 
land had become so feitile as to induce him to 
dispense Avith the use of manure; he has not 
since used it, and is now fully persuaded that 
its fertility is OAving to certain vapors arising 
from the heap and then descending on bis land. 
None of the soluble matters of the heap are 
earned to Mr. T.’s field, no manure has been 
applied, and its fertility continues unimpaired.” 
— Appendix to Liebig, p. 3G6. 
3. Plaster has been obseiwed to produce but 
slight effects upon old, dry and hide-bound mea- 
doAvs. Says Liebig, (p. 87,) “Water is abso- 
lutely necessar}' to effect the decomposition of 
gypsum, and also to assist in the absorption of 
the sulphate of ammonia by the plant.?: hence 
it happens that g}’psum is not obseiwable on dry 
fields and meadoAvs.” To which may be add- 
ed, that but a small quantity of putrescen; mat- 
ter existing in such cases, the exhalations are 
inconsiderable; and what is deposited from the 
atmosphere by deAA's cannot be absorbed by the 
soil in consequence of its compact, impenetra- 
ble surface. On old, and even dry pasture 
lands, the effect is much greater, there being CA'er 
present on their surface, a portion of manure to 
serA^e as a basis for its action. 
4. It has been universally observed that the 
most striking effect of plaster is on the cloA'er 
crop. Reasoii^“Pied cloA'^er contains double 
the quantity of nitrogen that common hay does.” 
— Gray,p. 158. 
5. It has occurred, in the experience of dif- 
ferent farmers, that AA'here one part of the field 
is soAvn with plaster immediately before a thun- 
der shower, and another directly after the same 
shower, the portion soAA’n first Avas benefited in 
a far higher degree than the other. Reason -- 
“Rain water must, at all times, contain ammo- 
nia, though not always in equal quantity. It 
must be greater in summer than in spring or 
AA'inter, because the interA'als of time between 
the shoAA'ers are greater. The rain ot a thunder 
shoAver after a long protracted drought contains 
the greatest .quantity which is convep'ed to the 
earth at any one time.” — Liebig, p. 73. 
6. Considering the beneficial effects of plas- 
ter at large, it has been obseiAnd that they de- 
pend, in general, not so much on any peculiari- 
ty in the location, or composition of soils, as on 
those physical conditions Avhich render the sur- 
face of the .soil an easy medium for the trans- 
ition of soluble matter: all of which must go to 
corroborate the theory in question. 
From the views thus presented, Ave are led to 
infer — 
1. That the atmosphere is an inexhaustible 
source of food for plants. 2. That the most 
av'ailable agent for .securing the benefit of this 
food to plants is piaster. 3. That vieAAnd in 
this light, the value of plaster in agriculture can 
hardly be over-rated. 4. Then it maybe safely 
recommended for general use on all soils con- 
taining a portion of fermentative matters, and 
not so compact or Avet, as to preA'ent the process 
of exhalation and absorption. 5. That it .should 
always be applied to the surface of the soil, or 
at least Avithin the influence of the atmosphere. 
6. That it should be soAA n at an earl}" date in 
the season, before the period of the most abun- 
dant dews and exhalations has commenced. 7. 
That it should always accompany manures 
used as a top dressing, or only slightly buried 
in the soil: and 8. That it should be liberally 
