196 
THE CULTIVATOR, 
June, 
supposed power of decomposing organic matter, altering 
the physical constitution of the soil, or of affording water 
to plants. 
Sir Humphry Davy and others, have proved that the 
decay of animal substances was not hastened by being 
mixed with gypsum; if it had possessed this property, 
and by this alone it was useful to plants, then it should 
prove most efficient on soils rich in organic matter, and 
add to the luxuriance of all plants. 
The quantity usually applied, from two cwts. to four 
cwts. per acre, is obviously too small to exercise much 
influence on the physical constitution of a soil; besides 
its beneficial effects have been observed on soils varying 
in texture from sand to clay. 
Yegetable mould, clay, and other substances in the 
soil, are known to have a much greater capacity for ab¬ 
sorbing moisture from the air, than gypsum. In two 
cwts. unburned, about 47 lbs only of water, are added to 
the soil, and supposing roots had the power of abstract¬ 
ing the water of combination, and that this could be con¬ 
tinually replaced, then if the supply of moisture afford¬ 
ed by gypsum was the chief cause of its influence, its 
effects should be most observable on the driest soils, and 
it should be of great benefit to all crops on most soils in 
dry seasons; but the facts at present known do not war¬ 
rant any such conclusion. A crop has been doubled by 
the use of gypsum, on the western coast of Scotland, 
where much rain falls, as well as on the sands of Holk- 
ham, in Norfolk, where the climate is comparatively dry. 
Liebig has stated that the influence of gypsum on the 
growth of grasses, depends on its fixing in the soil the 
ammonia of the atmosphere. There can be no question 
that gypsum has the power of fixing ammonia, or that 
the sulphate of ammonia produced by the mutual de¬ 
composition of gypsum and carbonate of ammonia, -is 
readily soluble in water, and a valuable food for plants. 
Before, however, it can be admitted that this is the sole, 
or even the chief cause of its influence, it should be 
proved to have the most decided effect on soils which 
contain least of other matters capable of combining with, 
or condensing ammonia, and that on these soils, a dress¬ 
ing of charcoal, or chloride of calcium, or substances 
containing ammonia, are equally efficient. 
Sir Robert Kane considered that the peculiar action 
of gypsum consists in its supplying lime for the rapid 
growth of clover, and other leguminous plants, which 
its moderate solubility in water enabled it to effect bet¬ 
ter than any other compound of that earth. It is pro¬ 
bable that gypsum may, in some cases, act chiefly by 
means of its lime, when sulphuric acid and an abun¬ 
dance of other matters required for the growth of plants, 
excepting lime, are present in the soil. But it seems 
somewhat paradoxical, that the rapidity of the growth 
of a plant should be in proportion to the slowness of the 
supply of one of its chief constituents. If lime, in the 
state in which it is usually applied, were so easily solu¬ 
ble as to be washed out of the land, or beyond the reach 
of the roots, before the plants had completed their 
growth, then a compound affording a more lasting, 
though limited supply of lime, might in the end prove 
more useful; but a dressing of ordinary lime is seen not 
only to carry through one crop, but to exercise an influ¬ 
ence on crops for years after; and if the action of gyp¬ 
sum depended solely upon its lime, then it should follow 
that it would be an useless application to calcareous soils, 
where this material already abounds. The reverse of 
this, however, seems to be the case, for some of the most 
decided instances of the beneficial action of gypsum, 
have been observed in chalk. In “ British Husbandry,” 
it is said “ experience has proved gypsum to be benefi¬ 
cial when laid upon limestone soils, or upon land which 
had been dressed with chalk or lime. It is used exten¬ 
sively for clover, sainfoin, &c., on the chalk formations 
in Kent, Hampshire and Berkshire. At Tanstall, near 
Sittingbourne, in Kent, situated, I believe, upon the 
chalk, a portion of clover was dressed with gypsum, at 
the rate of four cwts. per acre, and the aggregate pro¬ 
duce was three times as great as the other portion of the 
field, to which no gypsum was applied. It can hardly be 
conceded, then, that the lime supplied by gypsum is the 
sole or main cause of its fertilizing power. 
Sir Humphry Davy concluded that gypsum is an es¬ 
sential constituent of some plants, as it was always most 
beneficial to those which afforded it on analysis, and he 
considered that it might naturally exist in some soils in 
quantities sufficient for the wants of plants; consequent¬ 
ly a special application of gypsum to these soils, would be 
attended with little or no benefit. Other writers, as 
Russel, Johnson, &c., coincide in the opinion of Sir 
Humphry Davy that the benefit to be derived from an 
application of gypsum, will not only depend upon the kind 
of plant, but on the abundance or scarcity of gypsum 
or other sulphates in the soil. That sulphur contributes 
to the growth of plants, seems to be proved by the fact 
that sulphuric acid alone has in many instances proved 
beneficial. Vegetation has been observed to be luxuriant 
in the neighborhood of sulphureous springs. Natural or 
artificial waters which have a sulphureous taste, are said 
to give birth to a peculiarly luxuriant vegetation when 
they are employed in the irrigation of meadows. (John¬ 
ston.) In France sulphuric acid has proved to be a 
good manure when poured upon land after the removal 
of the crop. (Liebig.) Sulphur has been applied with 
advantage in Germany, as a top-dressing for clover and 
other crops, to which gypsum, in that country. is usually 
applied. (Cuthbert Johnson.) In experiments made 
on two fields by a Scotch farmer, sulphuric acid afforded 
a greater increase of hay than gypsum and an excellent 
crop of turneps has been raised by means of sulphuric 
acid in Fifeshire. 
Again, the experience of farmers generally favors the 
conclusion that gypsum acts most energetically on sain 
foin, clover, lucerne, and turneps, all of which contain a 
considerable proportion of sulphate of lime. Thus at Holk- 
ham .an application of 4 bushels per acre on sainfoin layers, 
is said to have doubled the crop. On a clayey soil in 
Hampshire, 2^ cwts. per acre were strewn on two year 
old sainfoin; the extra produce of hay at the first cutting 
Avas one ton per acre; in October the gypsumed part af¬ 
forded lif ton of hay, yet there was scarcely any on the 
rest of the land. In the next year the former was twice 
mown, vdiile in the latter, it is said there was nothing to 
moAV. On clover the influence of gypsum seems in some 
instances to be very decided. In an experiment made 
at Highstead, the simple soil produced one ton of clover 
hay and 20 lbs. of seed per acre ;< a portion of the same 
