December i, 1891.] 
THE TROPICAL AGRICULTURIST. 
4*3 
siutu sulphate familiar to as as Epsom salt. If in hydro- 
chloric (muriatic) acid, we put some metal, as sodium, in 
place of tlie hydrogen, we have a compound consisting 
of sodium and chlorine, which is the sodium salt of 
hydrochloric acid and is called sodium chloride, 
sonretimes muriato of soda, familiar tousas common 
salt. 
The wol’d “ palt, ’ u-s naed in clieiuiatry, applies to a 
great mimbur of compounds, and many ot the sub* 
stances we haveto deal witli in Rpeaking of fertilizers 
are chemical salts, that is, substanccH formed by put- 
ting some metal in place of the hydrogen of some 
acid. 
CAfiliON. 
Id. IiirouTANCK OK Carbon. — The element, carbon, 
may be called the central element of all animal and 
vegetable flubstancos ; for there is not a living thing, 
from the smallest cell to the giant tree, which does 
not contain carbon as a necessary constituent. That 
all vegetable and animal anhstoncea contain carbon 
can easily be shown by simply heating them sufficiently, 
and thus causing them to blacken or char. When, 
for exaniple, wood is heated, the different elements of 
which it is composed, are driven off in one form or 
another, but tho carbon is the last to go, and remains 
behind as a black substance orcharco^, unless heated 
higher, when it disappears or burns up. 
14. OccuRiiE.vcE OK Caiihon in Nature.— Carbon 
usually occurs in nature’ united into compounds with 
other elements. Thus, most products of plant life 
contain carbon combined with the elements nydrogeu 
and oxygen ; such are starch, sugar and cellulose or 
woody fibre, (’arbon, combined with oxygen, occurs 
in the air in the form of carbon dioxide, commonly 
called carbonic acid gas. Carbon, when combined 
with oxygon and some element such as calcium, occurs 
in the form of carbonates ; for example, marble, lime- 
stone and chalk arc choniically known as calcium 
carbonate or carlionate of lime. 
Carbon by itself or in tho free condition, that is, not 
united witli any other elements, is familiar to us in 
several different forms ; the most common of these 
forms are (1) diamonds; (2) graphite, which is used in 
the manufacture of lead pencils; (3) ordinary wood 
charcoal; (4) lamp-black; (5) animal charcoal; (fi) 
mineral cfial. Excepting diamonds these forma of 
carbon are more or less impure, containing some 
other things mixed with tho carbon. 
15. It is pertinent to make here tho inquiry, “What 
is tlio relation of carbon to fertilizers?" Before we 
can answer tliis question satisfactorily, we must know 
what is meant by a fertilizer and wnat must be re- 
garded as necessary constituents of a fertilizer. We 
mil, therefore, turn aside from our consideration of 
the element carbon and take tho opportunity, at this 
stage, to ^ive some definitions of general and special 
terms winch we shall have occasion to utsB more or 
less frequently. 
PKFINITIONS. 
16 . Fkutiuzer.— A s ordinarily spoken of, a ferti- 
be defined as any substance which, by its 
addition to tho soil, is intended to produce a better 
growth of plants. 
The materials which come under tho head of ferti- 
lizers aro numerous m kind, and differont both inform 
and in the manner in which they act. 
tabulated classification, while not 
strictly accurate m every respect, will serve to give a 
good general idea of the number and relations of tho 
terms used in speaking of fertilizers:— 
W 
f I. Direct^ 
1. Natural 
'Stable manure. 
llefuHC vegetable 
matter. 
Green Ci'ops for 
plowing under. 
Cotton Seed. 
LMuck, marls, etc. 
a. complete o: 
gonoral. 
h. incomptot< 
or special. 
_ f Commercial 
2 Aiaiiical-( Chemical 
II. Ijidirect 
r Ijiine. 
■< Gypsum. 
(Salt, etc. 
I. Broparod 
.4: 
ioal, I 
These terms are, in general, loosely and indiscrimi- 
nately used, as their meaning is often misunderstood ; 
and so an attempt will be made here to define them 
in accordance with the best usage of the terms. 
18. A direct fertilizer is one that contains elements 
of plant food which aro available at once, that is, 
which can be taken up and used immcdiatly by plants. 
19. The term available is applied to plant food 
which is soluble, tliat is, in snob a condition that 
the roota of the plant can take it up readily in 
solution. 
■20. Plant food is unavailaldo when it is in au 
insoluble from, so that the roots of tho plant fail 
to take up any part of it. A largo proportion of 
E lnnt food present in the soil is unavnilahlo, but, 
y tho action of air, water, carbonic acid, etc., it 
is gradually changed to soluble or available 
forms, which the plant can take up and use. 
As will bo noticed later, phosphoric acid in tho 
form of insoluble calcium phosphate, or phospliato 
of lime, is unavailable as plant food, but when con- 
verted into a super phosphate, or soluble calcium 
phosphate, it becomes available. Duavailahlo plant 
food is potential food or food in reserve. 
21. Au indirect fertilizer is one whioli does not 
furnish to the soil any needed plant food and which 
may not he a plant food at all, but which is 
characterized by tho w ay iu whicli it acta on the matter 
already in tlio soil, changing more or less of it from 
unavailable plant food to an available form. E'er 
example, lime, gypsum, salt, etc., are indirect foitili- 
zers, so far as they have any fertilizing action. 
Eater, some attontion will ho given to the action of 
some of tile most familiar indirect fertilizers. 
22. Natural fertilizers include tho solid and liquid 
excrement of animals, all kinds of vegetable rotuse, 
green crops for plowing under, cotton seed, mucks, 
marls, etc, 
23. Artificial fertilizers are also known by such 
names as commercial fertilizers, chemical fertilizers, 
prepared fertilizers, etc., and are artificial preparations 
or mixtures of fertilizing materials sold under trade 
names. The fertilizing materials used in making 
these mixtures include tho substances found in 
natural deposits and by-products of numerous iu- 
dustries, which are obtainable by farmers only 
tlirongh the channels of trade. Some substances 
which might Ijo classed as natural fertilizers, snch 
as cotton-seed meal and tobacco stems, are also 
included among the materials of artificial fertilizers. 
24. ^ Complete fertilizers, known also as genera^ 
fertilizers,^ are those' which contain nitrogen, plios" 
phoric acid and potash. 
2,'i. Inoomplote fertilizors, also called siieoial fertili- 
zers, ore tlioso which contain only one or two of 
tho tliree constituents, nitrogen, phosphoric acid and 
Iiotash. 
211 . Tliere is a common practice among farmers 
and dealers, of calling all commercial fertilizers “phos- 
phates,' regardless of whether they contain any 
phosphates at all or not. Tho practice is clearly 
objectionable, because a xihosphato is not the only 
fertilizing constituent present in commercial fertili- 
zers — in some cases it may be entirely absent. The 
term “super-phosphates" applies truthfully to many 
oomniercial fertilizers, lint even those cannot he 
correctly spoken of as simply “ phospliates. ” 
Having considered such definitions as we may have 
occasion to use more or leas ftoqueutly, wo can now 
return to 
Tlir. IlELATIONS OF CARRON TO FKRTlLIZIiRS. 
27. We know that carbon must he an important 
element in plant food, since it forms nearly one- 
half of the solid proportions of plants. Notwithstand- 
ing the fact that carbon forma so largo a portion of 
plants, it has no importance as an active food consti- 
tuent of direct fertilizers. This statemeut may appear 
strange and tlio question may he asked, “Why is 
not carbon to bo regarded as an essential constituent 
of direct fertilizers ? ” Tho answer is tlmt tho carbon 
of plants comes from tlio carbon dioxide (carbonic 
acid gas) of tho air, and the air furnishes an in- 
oxhausUblo and available supply of this subataaco.' 
