1851 
THE CULTIVATOR. 
197 
soil to which gypsum, at the rate of five bushels per 
acre had been applied, yielded a crop equivalent to three 
tons of hay and 105 lbs. of seed per acre. In British 
Husbandry, gypsum is said to have increased crops of 
clover and lucerne, on some soils in Kent, at least three 
fold. In Ayrshire, part of a crop of turneps was nearly 
doubled by the use of gypsum. In the same neighbor¬ 
hood, no perceptible effect was produced on turneps by 
2 cwts. of gypsum ; but the entire crop was excellent— 
a circumstance which should not be lost sight of when 
experimenting with special manures. There is a limit 
to the growth of plants; if a soil is already so rich in 
vegetable food, as to be able to produce a great crop, a 
dressing of any manure to a soil in such a state, would 
be useless. 
There are also many observations on record which 
seem to show that the growth of plants in some instances 
was checked owing to the want of gypsum in the soil, 
and that it acts much more powerfully on some plants 
than on others. Thus, if land is clover-sick; if the young 
plants spring up and die away as summer advances, this 
is considered by many to be an indication of the absence 
of gypsum. A crop of sainfoin which began to decline 
in the 4th year, became as productive as before by an 
application of gypsum. (Brit. Hus.) In the 5th year 
after sowing lucerne, the natural grasses appeared to be 
gaining ground, when a dressing of gypsum produced 
such a smothering crop that the grass could no longer 
make head, till after the third cutting. In another in¬ 
stance, an old grass field became gradually less and less 
productive in spite of all applications, when a quantity 
of peat ashes containing about 2 cwts. of gypsum, was 
afterwards applied, and a similar result followed,—-the 
grass not only grew with greatly increased vigor, but a 
quantity of white clover made its appearance in the part 
dressed, in so marked a manner as to attract the notice 
of the farmer. In both these cases the gypsum had 
evidently a much more powerful effect on the clover and 
lucerne than on the grass. 
So far, then, as my gleaning of facts and opinions ex¬ 
tends, it seems to me that all we can be said to know 
with any degree of certainty regarding the action of 
gypsum on plants is, that it does not depend upon the 
moisture it contains, or is capable of attracting from the 
atmosphere • nor on its supposed power of decomposing 
organic matter. We may also infer that it is most bene¬ 
ficial to clover and other leguminous plants, and that it 
probably acts more powerfully on them in consequence 
of the great proportion of sulphur they contain. If 
this be so, it is easy to understand why in some soils it 
may add to the growth of most plants. If a soil con¬ 
tains all other substances required for the perfect nourish¬ 
ment of plants excepting .sulphur, then a dressing of 
gypsum would have a visible effect on wheat, oats, &c., 
which require a comparatively small supply; and it 
•should follow that if the quantity naturally existing in 
a soil were so small as not to suffice for the wants of 
these plants, that clover, lucerne or sainfoin, which con¬ 
tain much sulphur, could not, previously to the applica¬ 
tion of gypsum, grow in a healthy condition. A difficulty, 
however, arises here; if this were the case, if the ex¬ 
haustion of the sulphur of a soil, were the only reason 
why gypsum is so beneficial on some soils, why clover 
and turneps cannot be repeated at short intervals with 
advantage; why do not these soils produce a similar ef¬ 
fect on the potato and cabbage, for the analyses of the 
ashes of these plants indicate that they require a very 
considerable quantity of sulphuric acid? yet there are 
few or no districts where the potato, at least, is not fre¬ 
quently repeated on the same land, but we do not hear 
of lands being tired of potatoes or potato-sick. 
The points on which more precise information seem 
to be required are the following: 
1. Does analyses show a deficiency of sulphate of lime 
in soils where an application of gypsum is efficient, and 
an abundance in those soils in which it is inert? 
2. Is gypsum on all soils beneficial to plants in pro¬ 
portion to the smallness of the quantity of sulphate of 
lime they contain? 
3. Does gypsum act by different means in different 
soils and on different plants? 
If it should be ultimately proved that the action of 
gypsum is chiefly due to the sulphuric acid which it con¬ 
tains, then a question will arise whether other sulphates 
or sulphuric acid, can be profitably substituted for gyp¬ 
sum on some soils or for some plants, as dilute sulphuric 
acid on chalk and limestone soils, or sulphate of potash 
for wheat, on land with sufficient lime. It would also 
be desirable to ascertain what are the chief causes of the 
difference in the quantity of sulphuric acid in soils— 
whether it is to be traced to a difference in the composi¬ 
tion of different rocks from which soils have been derived , 
and consequently whether a knowledge of the geology 
of a district will enable one, without the aid of analysis 
or experiment, to pronounce whether an application 
of gypsum will be profitable or otherwise. Or, may the 
difference depend partly upon the mode of cropping pur¬ 
sued in different districts—to the presence or otherwise 
of sulphureous springs—or is»gypsum conveyed to the land 
in unequal quantities in different localities in the ordi¬ 
nary dressings of lime? 
The following experiments seem likely to throw some 
light on the main questions. I propose that they should 
be tried in at least three districts. 1. Where gypsum 
is known to be of the greatest benefit. 2. Where it acts 
on certain plants only, as clover. 3. Where it is of lit¬ 
tle or no use to any plants. A field should be selected 
in each district, well drained, nearly level, of uniform 
quality, free from the shade of trees, and which had 
been manured and cropped throughout alike, for three 
or four preceding years. A complete analysis must be 
made of the soil of each field,previously to the commence¬ 
ment of the experiments. The same variety of each plant 
should be grown in the three districts; it is desirable, in¬ 
deed, that all should be supplied from the same sample. 
The culture of each plant must be alike throughout— 
all kept free from weeds—the land accurately measured 
and the entire produce of each patch carefully weighed. 
Notes should also be taken daily, of the state of the 
weather during the trial of these experiments—and, as 
will be seen hereafter, it is especially desirable that the 
time the gypsum remains on the leaves should be care¬ 
fully observed. I propose that a patch of most of our 
arable plants should be grown and top-dressed alike—say 
in the first week of June, with the following substau 
ces: 
