THE ACTION ON THE GROWTH OF CROPS OF
SMALL PERCENTAGES OF CERTAIN METALLIC
COMPOUNDS WHEN APPLIED WITH ORDINARY
ARTIFICIAL FERTILISERS.
BY WINIFRED B. BRENCHLEY, D.Sc.
(Rothamsted Experimental Station, Harpenden, Herts.)
(With Eight Text-figures.)
INTRODUCTION.
IN the course of a long series of experiments on plant nutrition, carried
out chiefly by means of water and pot culture tests, a considerable amount
of information has been obtained as to the action on growth of various
elements other than those commonly recognised as nutritive. These
elements have come into notice in various ways, frequently in correlation
with larger investigations upon quite other lines. In some cases this has
led to more specific tests, and copper, manganese, boron, zinc, arsenic,
silicon and iodine have been dealt with in previous publications^, 8,9).
Many of the rarer elements came under review in connection with the
investigation on boron (10), and it is hoped that opportunity will offer in
the future to extend these observations. Meanwhile, in view of the fact
that literature dealing with the effect of many elements on plant growth
is relatively scanty, it may be of value to other workers in the same field
if the results of further work with copper, and certain experiments with
vanadium, lithium, titanium and aluminium are put on record. It must
be emphasised, however, that the material here presented makes no
pretence to be an intensive study of any one of these elements, the aim
being to put forward data which may aid in any further investigation of
the subject.
COPPER.
In view of the known toxicity of copper to plants, and of the widespread use of copper compounds in combating plant disease, the question
of the effect on plant growth of the element when it is present in the soil
has. become one of considerable economic importance. It is recognised
that while copper compounds alone in solution are very poisonous if
supplied to the roots, the harmful action is greatly mitigated if nutrient
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WINIFRED E. BRENCHLEY
705
salts are also present (6). This reduction of toxicity is still more marked if
soil is the substratum, probably owing to the adsorption of much of the
copper compound, whereby it is removed from the soil solution and so is
rendered innocuous to plant roots. It is still a debatable question as to
whether concentrations of copper salts which are too small to be toxic
exert a stimulating action on growth. Results are conflicting, and it is
probable that the interaction of the many environmental factors involved,
together with the species and even the varieties of the plants grown, admit
of stimulation in certain cases and negative action in others.
The suggestion that small quantities of copper salts, if mixed with the
usual artificial fertilisers, might improve the growth and yield of crops,
led to a series of pot culture experiments being instituted at Rothamsted.
Voelcker(5i), working with wheat on the light soil at Woburn, had
already found a slight stimulation from the use of copper, applied as
sulphate or carbonate, ranging from 0-01 to 0-02 per cent, of the quantity
of soil used, larger amounts being definitely toxic. In these experiments
the soil was unmanured, and when they were repeated with a somewhat
richer soil (also unmanured) from another field the degrees of toxicity and
of stimulation were less marked, showing that soil influence is a factor
which cannot be disregarded.
The quantities of copper salts used in these Woburn experiments were
very heavy, 0-01 per cent, copper representing 3-93 gm. copper sulphate
(CuS04. 5H2O) per pot containing 10 kg. of soil, which represents a
dressing heavier than those of some of the regular artificial fertilisers
applied, and as the aim of the Rothamsted tests was to determine if
small additions of copper salts would inexpensively improve the action
of the usual fertilisers no attempt was made to utilise such heavy
amounts.
Experiments were carried out on two soils, one being a light and very
acid soil from Cheshire, deficient in phosphate and calcium, but well
supplied with sulphate, the other a heavy Rothamsted loam, containing
a sufficiency of calcium. Chalk was added to the Cheshire soil to compensate for the acidity and so avoid masking any possible action of the
copper sulphate. Four manurial schemes were adopted, with a basis of
superphosphate and with constant amounts of nitrogen and potassium in
the form of different fertilisers.
Manurial schemes.
1.
2.
3.
4.
5gm. superphosphate + 2-5 gm. ammonium sulphate+ 20 gm. potassium sulphate
5 „
„
+2-5 „
„
+6-06 „ sylvinite
5 „
„
+3-28 „ sodium nitrate
+2-0 ,, potassium sulphate
5 „
„
+3-28 „
„
+606 „ sylvinite
Journ. Agrio. Sci. xxil
46
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706
Action of Certain Metallic Compounds on Crops
Each of the above mixtures was combined with 0-5, 1, 2 and 4 per
cent, of copper sulphate based on the total weight of fertiliser supplied in
scheme 1, and in every case a unit of four similarly treated pots was used.
These represented 0, 0-0475, 0-095, 0-19, 0-38 gm. copper sulphate per
pot containing 10 kg. of soil. The percentages of copper sulphate were
based on the suggestion originally made by the Copper Sulphate Association that 1 per cent, or 2 per cent, might prove beneficial if mixed with
superphosphate or other fertilisers.
Goldthorpe barley was sown March 22, 1927, and harvested on
August 15. During growth no marked differences due to the copper
sulphate dressings were noted, though on a few occasions it appeared as
if the heaviest dose had a slightly detrimental effect which, however, was
temporary and not persistent. The figures relating to the harvested crops
show that the application of copper sulphate in the amounts here tried
were of little value on either the light or heavy loams tested. Some slight
evidence of increase in the yield of grain was obtained on the Cheshire
soil only, with the heavier dressings of copper sulphate, when sodium
nitrate was the nitrogenous manure applied, but this was not the case
with ammonium sulphate. In Table I the figures for both soils are given
for the manurial treatment of superphosphate, sylvinite and sodium
nitrate, as representing the case in which some evidence of effectiveness
of copper sulphate was obtained on the Cheshire soil. With the other
combinations of fertilisers the figures are still more level, and their
publication is unnecessary.
Table I. Barley treated with copper sulphate; superphosphate,
sylvinite and sodium nitrate as fertilisers. Average of four pots.
CuSO,
uSO4 +
5H2O
>er p o t
Dry weight (gm.)
{
(gm.)
Straw
Rothamsted soil:
Nil
3210
0-0475 32-44
0095
32-68
019
33-06
0-38
33-38
Cheshire soil:
29-87
Nil
0-0475 29-32
30-29
0-095
29-89
0-19
31-84
0-38
*
Actual N (gm.)
% N
\ i
•*
\
% dry in
green
Grain
Total
Straw
Grain
Straw
Grain
Total
Straw
Ears
21-49
21-80
20-59
21-58
21-90
53-59
54-24
53-27
54-64
55-28
0-385
0-374
0-408
0-386
0-389
1-74
1-81
1-74
1-66
1-69
01236
0-1213
01333
01276
0-1298
0-3739
0-3946
0-3583
0-3582
0-3701
0-4975
0-5159
0-4916
0-4858
0-4999
34-2
33-6
34-4
33-9
35-3
82-4
821
801
80-8
72-2
2101
22-70
21-58
22-72
24-66
50-88
52-02
51-87
52-61
56-50
0-571
0-595
0-559
0-548
0-557
2-21
2-14
2-19
215
2-00
0-1705
01745
01693
01638
0-1774
0-4643
0-4858
0-4725
0-4884
0-4932
0-6348
0-6603
0-6418
0-6522
0-6706
35-0
37-3
34-4
35-4
35-4
820
81-2
81-9
80-3
79-0
The percentages of nitrogen in the straw and grain show no variation
that can be correlated with the copper sulphate dressings, and the actual
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WINIFRED E. BRENCHLEY
707
amounts of nitrogen present in the harvested crop vary comparatively
little within each manurial treatment. The maturity of the straw, as
indicated by the percentage of dry matter present at harvest, also showed
no influence of the copper sulphate treatment, though it was affected by
the type of manuring.
The differences in yield, maturity and percentage of nitrogen induced
by the various forms of artificial fertilisers were considerable, emphasising the desirability of continuing to carry out any further work with
copper compounds with different combinations of manures as well as on
different soils, as it is quite conceivable that interaction between copper
sulphate and manure might come into play and have some influence,
beneficial or otherwise, on plant growth.
Similar tests were made in the same soils with another variety of
barley (Archer Goldthorpe x Goldthorpe Spratt) in which Bordeaux
mixture containing 32-5 per cent, copper was used instead of copper
sulphate, the heaviest dressings being raised to supply copper equivalent
to double the amount used in the first experiment. The actual manurial
treatment for each soil was as follows:
5 gm. superphosphate, 2-5 gm. potassium sulphate, combined with
Bordeaux mixture
2-5 gm. sulphate of ammonia
3-218 gm. sodium nitrate
gm.
0
0
gm.
0-148
0148
gm.
0-295
0-295
gm.
0-59
0-59
Each treatment was replicated four times and the whole series was
systematically randomised in arrangement to avoid errors arising from
differences in position in the culture house. Observations during growth
and comparison of the yields showed that the addition of Bordeaux
mixture to complete fertilisers had no beneficial effect on the growth of
barley in the two soils tested, the previous suggestion that heavier
dressings might be beneficial not being borne out, at least when the
copper was supplied in this form.
For comparison with the copper sulphate results the figures with
sodium nitrate manuring are given in Table II. Nitrogen determinations
were not made in this case, but average heights and number of ears are
included to show how little they were affected by the copper treatment.
It was considered unwise to attempt to increase the quantity of copper
compounds further, as the heaviest dressing here used corresponds
approximately to 1 cwt. per acre, which is probably approaching the
danger limit in view of the known toxicity of copper compounds.
Parallel experiments to those with barley were conducted in autumn
46-2
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708
Action of Certain Metallic Compounds on Crops
Table II. Barley treated with Bordeaux mixture; superphosphate, potassium
sulphate and sodium nitrate as fertilisers. Average of four pots.
Bordeaux
Av.
mixture height
per pot per pot
(gin.)
(cm.)
Rothamsted soil:
Nil
100-0
0148
1010
0-295
100-5
0-590
101-5
Cheshire soil:
Nil
92-0
0148
93-5
0-295
920
0-590
94-5
Av.
no.
ears
per
plant
Dry weight (gin.)
,
*
,
Straw
Ears
Total
% dry in green
,
*—
Straw
Ears
Total
9-2
9-5
9-8
9-6
3116
34-20
34-01
32-80
33-76
3411
35-45
35-48
64-92
68-31
69-46
68-28
39-47
4311
39-87
38-52
76-22
7505
74-57
74-21
52-68
54-74
52-29
51-35
9-4
8-8
8-8
9-3
28-88
28-58
27-50
2811
30-71
22-73
31-93
32-62
59-59
61-31
59-43
60-73
67-43
72-98
66-49
64-58
88-81
89-87
89-46
89-20
76-99
81-12
77-13
75-82
with mustard, as representing a crop that is cut in the green stage instead
of when it has reached maturity and ripened seed. The results were
identical, as in no case was any beneficial result obtained with copper
sulphate or Bordeaux mixture with any of the manurial combinations
supplied. Nothing would be gained from a detailed account of these
mustard crops, but for comparison the figures of the results are given in
Tables III and IV to correspond with those set out for barley in Tables I
and II.
Table III. Mustard treated with copper sulphate; superphosphate,
sylvinite and sodium nitrate as fertilisers. Average of four pots.
CuSO4 + 5H2O
per pot (gm.)
Bothamsted soil:
Nil
0-0475
0-095
0-19
0-38
Cheshire soil:
Nil
00475
0-095
0-19
0-38
Av. height
per pot (cm.)
Green weight
(gm-)
Dry weight
(gm.)
% dry in
green
67-42
67-96
68-46
67-34
63-88
135-45
136-96
139-26
135-22
13202
13-69
1317
1301
13-83
11-95
1011
9-62
9-34
10-23
906
49-50
58-04
57-33
55-83
45-50
95-57
129-91
124-47
12405
9917
7-20
8-51
9-01
9-62
7-41
7-53
6-55
7-24
7-76
7-47
While these experiments were in progress Allison, Bryan and
Hunter (i) published their startling results on the improvement in growth
effected when very small dressings of copper sulphate were applied to raw
saw-grass peat in the Everglades of Florida. While this land is naturally
so inimical to the growth of most crop plants that they usually fail com-
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WINIFRED E. BRENCHLEY
709
pletely soon after planting, the application of as little as 30 lb. per acre
of copper sulphate was found to encourage good growth and the production of useful crops. The results, as indicated by photographs, are most
striking, and are much more clearly marked with copper than with any
other of the elements, manganese, boron, chromium, arsenic, zinc, etc.,
that were tested simultaneously. Fifty-nine species of plants, well
distributed over nine well-defined groups, were tested, and with all of
them marked stimulation was obtained with copper sulphate. In many
cases heavy fruiting plants were produced when check plants grown
without copper sulphate failed entirely. Tomatoes showed a particularly
good response, and with peas the pods filled out much better. Also,
second crops of corn and sorghum grown on the same soil without further
addition showed a marked residual effect of the copper sulphate. Attention is drawn to the fact that no manure other than the copper salt was
applied to the peat, which is not acid, but has a high lime content, unlike
most peaty deposits.
Table IV. Mustard treated with Bordeaux mixture; superphosphate,
potassium sulphate and sodium nitrate as fertilisers. Average of four pots.
Bordeaux
mixture per
pot (gin.)
Bothamsted soil:
Nil
0148
0-295
0-590
Cheshire soil:
Nil
0148
0-295
0-590
Av. height
per pot (cm.)
Green weight
(gm.)
Dry weight
(gm.)
% dry in
green
80-46
84-65
8608
81-38
133-95
15118
150-65
137-70
20-49
23-43
21-72
20-44
15-30
15-50
14-42
14-84
77-91
79-85
85-23
70-46
160-60
148-30
148-33
137-23
23-20
19-71
22-75
19-43
14-45
13-29
15-34
1416
In view of these American results, tests were carried out on English
peats. Nothing resembling the saw-grass peat is obtainable in this
country, but the work was done with a fenland peat from Suffolk, with a
pK value of 7-75, contrasted with a typical acid peat from Dartmoor of
pH 4-57. Pot culture experiments were made with barley, rye and turnips, copper sulphate at the rate of 0-8 gm. per pot being added to one
half of two series grown with and without artificial fertilisers, the
remainder receiving no copper dressing. Owing to the difference in the
constitution and the water content of the two peats as delivered, each
pot contained 5 lb. of acid Dartmoor peat or 16 lb. Suffolk peat when
filled to the same level. The two peats were utterly different in nature,
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710
Action of Certain Metallic Compounds on Crops
that from Dartmoor being a true fibrous peat, which was broken up and
finely sieved, whereas that from Suffolk was more like a dense black
loam, of a very light nature. The manurial scheme throughout was as
follows:
| Superphosphate 5 gm.
Fertilisers per pot, where applied J Ammonium sulphate 2-5 gm.
{Potassium sulphate 2 gm.
Combination of manures and copper sulphate
A
No CuS04 + 5H2O
No manure
B
WithCuSO4 + 5H2O
No manure
C
No CuSO4 + 5H.O
With manure
D
WithCuSO^ + SHjO
With manure
Barley.
Archer Goldthorpex Goldthorpe Spratt seed was sown on February 29
and germinated satisfactorily in both soils. Throughout development the
plants in the acid peat were the more healthy, and they ripened a fortnight earlier than on the alkaline soil (July 30 on acid, August 13 on
alkaline peat). Nothing comparable to the Florida results was obtained
as regards the failure of this or any other crop to grow in the peat unless
small amounts of copper sulphate were added. Growth was very irregular
on both soils and the variations between duplicate pots were so large that
no reliance can be placed upon the mean figures, which are therefore not
published in case false conclusions should be drawn therefrom. These
variations were unavoidable, as owing to the peculiar water-holding
capacity of the peat, coupled with the ease with which water is lost by
evaporation, especially from the acid peat, the soil tends to "pack"
differently from pot to pot, rendering the experimental conditions much
more irregular than when ordinary loam soil is used for similar experiments. It was, however, evident that though the use of a mixed fertiliser
increased the yield and the amount of nitrogen passed into the crop, the
action of copper sulphate was probably negative, as the variations in
green and dry weight, nitrogen content, etc., in the presence and absence
of copper sulphate were very irregular and varied in either direction. The
height of the unmanured plants was appreciably increased by the use of
copper sulphate, but this effect was masked in the presence of fertilisers.
On the alkaline peat the leaves became yellowish at an early age and
eventually were streaked and spotted with brown, the whole plant becoming increasingly unhealthy in appearance. The whole set inclined to a
"spread-eagled" habit, instead of growing upright as is normal. The
earing shoots were later in appearing than on the acid Dartmoor peat,
and the ears seemed to be smaller and more behindhand in development.
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WINIFRED E. BRENCHLEY
711
Maturation was delayed and the plants were not ready for harvesting
until a fortnight after those on the acid peat.
Copper sulphate had no evident effect upon dry weight yields nor
upon total nitrogen content. The yields were not increased by the
addition of complete fertilisers on this soil, though the nitrogen content
was considerably raised.
Rye.
Garton's seed sown on February 29 was ready for harvesting from
both soils on September 18. Throughout growth the difference in
appearance with the various treatments was not very obvious. The
plants receiving manure tended to be rather stronger than those without,
and the plants on alkaline soil to be taller than those on acid peat
(Figs. 1, 2). On the acid peat the addition of copper sulphate caused
appreciable increase in height in the unmanured plants and a certain
increase, which might possibly be significant, in those receiving fertilisers.
This result with the unmanured plants tallies with that obtained with
barley. On the alkaline soil a slight increase in height occurred with
copper sulphate on unmanured plants, though it is doubtful if it was
sufficiently large to be significant, but no rise occurred in the presence of
fertilisers. The same criticism of the variety of the mean results applies as
with barley, but here again it seemed evident that copper sulphate had
no significant action in improvement of growth.
Turnips.
Carter's "Snowball" was sown on August 23, and harvested on
December 10, the behaviour of the crop in the two peats being radically
different from the outset.
On the acid peat germination was considerably delayed and the
seedlings were yellowish, growing very slowly and poorly at first. A
considerable improvement set in during October, but the plants were still
very small at harvest time. One noticeable feature was the entire
absence of fungus disease on the leaves, whereas those in the alkaline peat
were covered with white patches due to attack.
In the absence of fertilisers an increased yield was obtained with
copper sulphate, but this may have been influenced by the very bad
start made by the plants. Fertilisers induced some yield increase which
is more likely to be a true effect, judging by the appearance and growth
of the plants. The percentage of nitrogen in the whole plant was very
little influenced either by the fertilisers or the copper sulphate, and
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712
Action of Certain Metallic Compounds on Crops
Fig. 1. Eye grown on acid peat. Left to right: no manure, no copper sulphate; no manure,
with copper sulphate; with manure, no copper sulphate; with manure, with copper
sulphate.
\
\
Fig. 2. Rye grown on alkaline peat. Left to right: no manure, no copper sulphate; no
manure, with copper sulphate; with manure, no copper sulphate; with manure, with
copper sulphate.
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713
WINIFRED E. BRENCHLEY
consequently the total nitrogen taken up followed the irregular yields
with the different treatments.
On the alkaline peat germination was rapid and the seedlings grew
well, soon making large plants with dark green leaves, in striking contrast
to those in the acid peat. In this case, the only one in all the experiments
that may exceed experimental error, a heavier yield was obtained by the
addition of copper sulphate to complete fertilisers. The increase was
obtained in both leaves and "bulbs" of the duplicate pots, and it is just
possible that this is a true result, and the figures are therefore given for
reference (Table V). No similar increase was obtained when no manure
was added. In this case the percentage of nitrogen when fertilisers and
copper sulphate were combined was rather lower than with the other
treatments, which all gave parallel results. Even so, the total nitrogen
absorbed was considerably greater owing to the marked increase in yield.
Table V. Turnips, grown with and without copper sulphate and
complete fertilisers. Means of duplicate pots.
Green weight (gm.)
Leaves
Dry weight (gm.)
A
.. .
"Bulbs" Leaves " B u l b s " Total
Acid peat:
No Cu +no manure
Cu+no manure
No Cu + manure
Cu + manure
Alkaline peat:
No Cu+no manure
Cu + no manure
No Cu + manure
Cu + manure
Actual N
% N in in total
total
dry
dry
1 mfiiij i/ci.
matter (g m -)
24-81
37-93
43-82
4001
3-67
4-30
9-26
4-20
2-58
4-24
5-44
4-97
0-41
0-45
0-94
0-47
2-99
4-69
6-38
5-44
5-08
5-16
5-24
518
0-152
0-242
0-334
0-282
104-63
138-84
100-87
16815
5803
40-18
37-75
96-27
15-55
17-96
18-34
24-67
4-20
3-23
315
819
19-75
2119
21-48
32-86
4-54
4-56
4-51
3-73
0-896
0-966
0-969
1-226
Summing up these results it was quite obvious that, in spite of the
general irregularity in growth with all crops, no parallel result was
obtained to that of Allison, Bryan and Hunter (i) by the addition of copper
sulphate to unmanured peat, whether alkaline or acid in reaction. In no
case did the copper sulphate cause any improvement which might exceed
experimental error.
With barley and rye copper sulphate was also of no benefit when added
with a complete fertiliser. With turnips, however, a certain definite increase of crop was obtained which may possibly have been influenced by
the copper sulphate, though this assumption needs confirmation.
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714
Action of Certain Metallic Compounds on Crops
VANADIUM.
. In connection with the use of various types of slag as fertilisers,
investigations were made in 1924 and 1925 on the effect of the degree
of the fineness of grinding of the slags on their value as phosphatic
manures. Theoretically, finer grinding should tend to increase the
manurial value of slag by aiding the availability of the contained
phosphates. Actually, it was found in pot experiments that this was not
always so, but that in some cases the more finely ground slags were less
effective than the coarser grindings.
The experiments were carried out in Rothamsted soil, mixed with
10 per cent, sand to lighten it, with an adequate basal dressing of
nitrogen and potash (as ammonium and potassium sulphate) throughout.
The slags, ground to three degrees of fineness, were used in quantities
supplying phosphate equivalent to that in the superphosphate given to
the control pots, a second set of controls receiving no phosphate at all.
Barley and mustard were each grown for two seasons, the total crop
results being set out in Table VI.
Table VI. Barley and mustard grown with slag ground to three degrees of
fineness. Basal dressing of sulphates of ammonia and potash. Dry
weight (total). Mean offour pots.
Barley (gin.)
Slag passing sieve of mesh 100
120
t>
180
No phosphate
Superphosphate
1924
Oold
\J(\Jl\l.~
thorpe
52-72
52-60
52-73
59-79
60-48
1925
Spratt
Archer
35-81
39-22
38-31
30-77
43-82
Mustard (g m -)
1924
18-51
17-00
17-33
10-73
19-01
1925
15-47
1507
13-70
9-49
18-58
In 1924 the addition of phosphate was superfluous to the Goldthorpe
barley, equal crops being obtained from the two sets of controls. In the
presence of slag, however, the yield was considerably reduced, and as this
could not be attributed to any failure in the phosphate supply, suspicions
were aroused as to the possibility of some toxic agent being present in the
slag. This was corroborated to some degree the following year, and
strengthened by the behaviour of the mustard in which the yield
decreased with the increased fineness of the slag. Similar indications,
though less marked, were obtained with another slag, and as analysis
showed the presence of a certain quantity of vanadium in the slag, steps
were taken to determine the action of this element on growth.
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WINIFRED E. BRENCHLEY
715
Seedlings of Spratt Archer barley were set up in water culture early
in March, in the usual Rothamsted nutrient solution to which vanadium
chloride (VOC12) had been added to give a range of concentrations from
1: 5000 to 1: 15,625,000. The concentrations were planned to decrease
geometrically by £, but a few interpolations were made at possible
critical points.
With 1: 5000 VOC12 the seedlings were seriously checked from the
first, very little growth was made, and within six weeks they were quite
Fig. 3. Barley grown in nutrient solution with vanadium chloride.
Left
Control; no vanadium chloride
Middle 1 : 3,125,000 vanadium chloride
Eight 1 : 25,000
dead. With 1: 25,000 VOC12 signs of injury soon became evident, as root
growth was checked and less roots were produced, though the shoots
developed normally at first. Later on weakness became manifest in the
shoots, less tillers were formed, and though the plants developed in a
normal way a slight depression persisted throughout and was indicated by
a lowered dry weight at harvest (Fig. 3). A similar depression in the shoot,
becoming less marked with decreasing concentration, was shown down
to and including 1: 2,000,000 VOC12, but the dry weight of the next two
sets was probably affected by an unhealthy black affection of the root
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716
Action of Certain Metallic Compounds on Crops
which obscured the true vanadium effect. In the roots no sign of adverse
effect was observed in lower concentrations than 1 : 25,000 VOC12.
The lowest strength of all, 1: 15,625,000 VOC18, gave plants parallel to
the controls, without any indication of stimulation (Fig. 4). •
gm.
I8 r
15
10
Fig. 4. Dry weights of barley grown ia nutrient solution with vanadium chloride, March 9June 12.
o, Control
/, 1 : 1,000,000 vanadium chloride
b, 1 : 15,625,000 vanadium chloride
g, 1 : 625,000
c, 1 : 10,000,000
h, 1 : 125,000
d, 1 : 3,125,000
i, 1 : 25|000
e, 1:2,000,000
j , 1:5,000
The depressing effect on plant growth of minute traces of vanadium
was thus clearly demonstrated, and the water culture results lend considerable support to the assumption that the presence of this element was
responsible for the failure of finely ground slags to give as good manurial
results as superphosphate containing the same amount of phosphate.
Among earlier workers Ramirez (31) found that vanadium can be absorbed
and stored by plants, with resulting anomalies in growth, while Ducloux
and Cobanera (14) working with Pisum sativum indicated that the effect
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WINIFRED E. BRENCHLEY
717
of vanadium on root growth is depressing, often to a considerable extent,
whereas any possible stimulation is slight and is confined to the leaves,
which may show traces of the element as a storage product. This proved
toxicity of vanadium may be of more economic importance than has
hitherto been recognised, as the element is a recognised constituent of
certain soils. Robinson (36) reported from 0-01 to 0-08 per cent, in all of
a number of important American soil types, similar evidence being
furnished by Thomas (46) for Pennsylvanian soils, and doubtless further
analyses would reveal its presence in many soils in other parts of the
world.
LITHIUM.
The presence of lithium in plants has been recognised for many years.
Gaunersdorfer(i7) showed that for some plants this element is a constant
though not necessary constituent, and some years later Tschermak(47)
made a wide search for the element, finding it in forty-five species,
distributed throughout seventeen natural orders, notably Compositae,
Solanaceae and Ranunculaceae. His list of plants examined, but found
to be/ree from lithium, ran into hundreds, indicating that the element is
by no means of universal distribution in the plant kingdom. Robinson,
Steinkoenig and Miller (37) found lithium present in spectroscopic
quantities in all plants in forty-eight species embracing a range of
legumes, vegetables, grasses, trees and bushes.
Gaunersdorfer's work on Cicer arietinum, Viciafaba, Glycine hispida,
Tropaeolum, Salixfragilis, etc., indicated that for most plants lithium is
poisonous in relatively small quantities, but that a measure of protection
is afforded by the fact that the fully grown leaves are affected, and that
the lithium compounds if presented in low concentrations do not enter
the younger leaves or the meristematic tissues. The poisoned older
leaves shrivel and die, thereby removing part of the harmful metal from
the plant and from the soil.
The accumulation of lithium in the older leaves was corroborated by
Petri(30) who worked on olive trees and found that the chlorophyll of
affected leaves was partly destroyed, and the lamina dried out if sulphate
of lithium or certain other toxic compounds was added to the usual water
supply. Gaunersdorfer stated that lithium travels upwards with the
transpiration current and also in a lateral direction by way of the woody
cell walls. Rankin(32) provided further evidence of this by feeding
chestnut trees with solutions of lithium nitrate, when it was found that the
compound penetrated to all parts of the trees where active translocation
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718
Action of Certain Metallic Compounds on Crops
of food materials occurred, i.e. to all parts of the bark and sapwood
both above and below the point of insertion of the lithium nitrate, while
in small trees complete penetration of the heart-wood was obtained.
Attempts were made by Rumbold(38) to utilise this fact for the control of
the devastating chestnut blight (Endothia parasitica) by injecting toxic
salts into the trees. Lithium carbonate and lithium hydroxide were at
first efficacious, as a callus formed between the diseased and the sound
tissues, the former eventually drying out. The lithium, however, was
gradually eliminated from the trees, which thereupon became subject to
reinfection.
Ravenna and Zamorani (34), and later Ravenna and Maugini (33),
investigated the possibility of replacing potassium by lithium as a
nutrient element, and demonstrated the harmful effect of lithium on
Various plants which differed in the degree of injury exhibited, soy beans
being the most, and maize the least susceptible among the plants tested.
Experiments with tobacco, supplied with varying amounts and proportions of potassium and lithium salts, gave some indication that this plant
may be able to utilise certain small proportions of lithium salts. On the
other hand, Hahn(i8) reported that lithium compounds in the presence of
potassium compounds do not influence the growth of wheat in water
cultures during the first period of vegetation, whereas in the later period
the growth of the plants is rather retarded and the formation of grain
prevented.
The most detailed work as to the action of lithium on wheat and
barley was carried out by Voelcker(50) at Woburn from 1900 to 1912 in
connection with the Hills Pot Culture Experiments. Several compounds
were tested, the general results being that all concentrations above
0-0018 per cent, of lithium in the soil were increasingly toxic, retarding
germination and reducing yield. Smaller quantities of lithium given in
the form of phosphate, carbonate and especially nitrate appeared to have
some stimulating action, improving growth and increasing yield, 0-001
per cent, lithium being the effective amount. At the same time that
Voelcker was demonstrating the possible stimulating effect of lithium
compounds when added to soil, water culture experiments were being
carried on at Rothamsted to determine the action of lithium chloride
when the factor of absorption of the toxic compound, such as occurs in
soil, was eliminated. Barley was grown in a complete nutrient solution1
(Rothamsted^-yH 3-6) with the addition of 1: 10,000 to 1: 20,000,000
1
KN0 3 , lgm.; MgSO4, 0-5 gm.; KHjPO,, 0-5 gm.; NaCl, 0-5 gm.; CaSO4, 0-5 gm.;
Fe2Cl6, 0-04 gm.; distilled water to make up 1 litre.
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WINIFRED E. BRENCHLEY
719
parts of lithium chloride. No change of solution was made during growth,
and the plants were harvested after 43 and 53 days respectively in spring
and summer tests (March 8-April 20, May 7-June 29).
In the spring test the growth of the shoots did not appear to be much
affected by any concentration of lithium chloride, and the dry weights
showed no differences that could be regarded as significant. With
1: 10,000 lithium chloride the roots were adversely affected, being
thickened, short and bunchy, tending to remain at the surface of the
nutrient solution instead of entering it freely. Nevertheless, they were
among the heaviest in dry weight of the whole series. Improvement in
type of root development occurred with decrease in lithium chloride
concentration, those in 1: 100,000 lithium chloride being quite normal.
The difference in the total dry weights in the various concentrations did
not follow any regular sequence, and it was not possible to attribute any
toxic or stimulant action to the lithium chloride, though the higher
figures with some of the greater dilutions may be referred to on account
of later results (see Fig. 5). Similar stunting and thickening of the roots
of barley had previously been recorded by Voelcker(49) for plants grown
in water culture containing 1: 5000 and 1: 10,000 parts of oxide or iodide
of lithium, the injurious effect being more marked with the latter, which
introduced a second harmful factor in the iodine present.
In the summer test at Eothamsted the thickening and bunchiness of
the roots with the stronger lithium chloride concentrations were not
noticeable, but with 1 : 10,000 the tips of the lower leaves were much
discoloured, becoming yellowish brown, suggestive of typical injury by
poisoning. The general growth and the dry weight showed no definite
response to any concentration except 1: 10,000,000 lithium chloride. In
this case the plants were much above average strength, with sturdy
shoots and well-developed roots. So much growth had been made that
the plants were nearing the end of their nutritive resources in the
unchanged solutions, as was evidenced by a tendency to redness in the
stem colour, which in barley is a typical sign of shortage of some essential
nutrient, as nitrogen or phosphorus. The dry weight of both root and
shoot was more than double that obtained with any other strength of
lithium chloride or in the controls without lithium (Table VII, Fig. 5).
The increased dry weight was proportionally greater in the root than in
the shoot, and is clearly indicated by the reduction in the shoot/root ratio
as compared with that in other concentrations.
The tolerance of barley for lithium chloride in the presence of
nutritive salts is therefore considerable. This is shown still more clearly
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Table VII. Barley grown with lithium chloride (mean of five
plants). May 1-June 29.
Dry weight (gm.)
Shoot
0-793
0-857
0-752
0-684
0-751
0-632
0-829
1-861
0-771
Control; no LiCl
1: 10,000
LiCl
1 : 50,000
1 : 100,000
,
1: 500,000
,
1: 1,000,000 ,
1 : 5,000,000 ,
1 : 10,000,000 ,
1: 20,000,000 ,
gm.
0-977
0-863
0-795
0-851
0-710
0-944
2-214
0-867
Shoot/root
ratio
7-48
714
6-77
616
7-51
8-10
7-21
5-27
803
SPRING , March-April
1-0 -
I
Total
0-899
Boot
0106
0120
0111
0111
0-100
0-078
0115
0-353
0096
Totnl
S
__^,«•"
•5
— x — '.
X
x—— x — » _
SUMMER, May-June
Fie 5 Dry weights of barley grown in nutrient solution with lithium chloride, March 8'
April 20, May 4-June 24.
a, Control
'
/. 1 : 500,000 lithium chloride
ft' 1 :20,000,000 lithium chloride
g, 1 : 100,000
„
c, 1 : 10,000,000
„
K 1 :50,000
d, 1:5,000,000
„
«. 1 : 10,000
e, 1 : 1,000,000
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721
WINIFRED E. BRENCHLEY
by comparison with plants grown in similar solutions with a stronger
poison such as copper sulphate.
Concentration
1 : 10,000
Lithium chloride
Growth not affected
1 : 5,000,000
Growth not affected
Copper sulpliale
Plants killed outright, no development of seedlings
Much depressed. Dry weight
less than half that of control
plants
Buckwheat, grown in similar solutions from May 4 to June 4, was,
however, severely injured by 1: 10,000 lithium chloride, the shoots being
killed or very weakly, all the lower leaves being dead, while the roots
were extremely poor and undeveloped (Fig. 6). The appearance of the
gm.
•6
•5
•4
•3
•2
•1
0
Pig. 6. Total dry weights of buckwheat, grown with lithium chloride, May 4-June 4. Same
concentrations as for barley, Fig. 5.
dead leaves suggested a deposit of poisonous salts therein, but with
weaker strengths from 1: 50,000 lithium chloride downwards, no signs of
similar injury were manifested. No suggestion of stimulation, as occurred
with 1: 10,000,000 concentration in the summer barley tests was
obtained, the dry weights varying considerably among themselves, with
no regular sequence.
TITANIUM.
Titanium appears to be one of the most generally distributed of the
rarer elements in plants. Robinson, Steinkoenig and Miller (37) determined its presence in very small amounts in every species they examined,
forty-eight in all, covering a great variety of types. Bertrand and Spirt (5)
carried out more comprehensive analyses, their results leading them to
suggest that titanium occurs in all phanerogamic plants, largely in the
leaves and green parts. Some seeds are very rich in titanium, which is
almost entirely localised in the integuments, parenchyma tissues usually
Journ. Agric. Sci. XXIT
-47
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722
Action of Certain Metallic Compounds on Crops
being poorly supplied. In some cases relatively large quantities are
present, the most notable instances being:
Mate, leaf and stem
Strawberry, fruiting receptacle
Theobroma Cacao, seed
...
Maize, grain
...
Carrot, leaf
2332-0 mg. in 1 kg. ash
967-0
„
878-0
„
109-0
„
200-0
And for comparison:
Carrot, root
Wheat, grain
Oats, grain
Barley, grain
...
...
...
75-0
„
45-0
35-5
33-6
„
„
„
Askew (2), after determining the titanium content of New Zealand
soils and plants, found that soils reputed to give rise to bush sickness in
cattle contained a very low proportion of titanium, and suggested that
some association may exist between the presence of this element and the
production of pasture suitable for healthy animal development.
In view of certain suggestions that small quantities of titanium compounds, if added to the ordinary combination of artificial fertilisers,
might increase their efficiency and result in increased crop yield, pot
culture experiments with mustard were carried out in 1930 on two soils.
These were the same as were used in the experiments with copper (see
p. 705) and the general treatment was similar. Ground titanite (B) and
a compound titanium fertiliser (A) of similar composition1 were tested,
both alone and in conjunction with other artificial manures, applied at
the rate of
1-2 gm. per pot of titanium compound,
3-0 „ superphosphate,
2-5 „ potassium sulphate,
2-5 ,, sodium nitrate.
(
As the Cheshire soil is very deficient in lime, some pots were put up
without lime to determine whether the hme in the titanium compound was
beneficial, though this was known to be unlikely on account of the smallness of the dressing. Mustard was sown on May 22 and harvested July 18.
On the light Cheshire soil the plants grown without lime were hope1
Lime, 28-3 per cent.; silica, 30-3 per cent.; titanium oxide, 40-4 per oent.j manganese
peroxide, 1-0 per cent.; total, 1000 per cent.
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723
WINIFRED E. BRENCHLEY
lessly small and stunted, and the addition of titanium fertiliser had no
effect. Liming, without manure, caused a certain improvement, which
was much augmented by dressings of artificials, but here again no increased benefit was obtained from the use of titanium fertilisers. This
was the case as regards the dry weight percentage and actual quantity of
nitrogen taken up, and in the ratio between the dry and green weights of
the plants at harvest time.
Where the plants were abnormally small, as when no lime was given,
more plants were left per pot to give every possible opportunity for the
titanium fertiliser to show its action on growth. For a strict comparison
with better grown plants, therefore, thefiguresin these cases are probably
higher than they should be, but as the discrepancy was already so great
this is of no account. A consideration of the figures in Table VIII show
that in this soil mustard received no benefit from the use of either of the
titanium fertilisers.
Table VIII. Cheshire soil. Average results from t•hre'e
Av.
height Green
per pot weight
(cm.)
(gm-)
i<i u m i l e •
Titanium fertiliser, A
Titanite, B
No manure
Full artificials
A + full artificials
B + full artificials
With lime:
No manure
Full artificials
A + full artificials
B + full artificials
13-9
8-3
23-2
20-2
22-7
19-7
1-80
1-27
100
4-45
3-28
0-288
0-186
0152
0-701
0-689
0-566
40-9
731
67-8
76-9
28-90
87-00
92-60
87-30
4-270
16-910
17-960
16-760
405
Table IX. Rothamsted soil.
Titanium fertiliser, A
Titanite, B
No manure
Full artificials
A + full artificials
B + full artificials
Dry
weight
(gm.)
Av.
height Green
per pot weight
(cm.)
(gm.)
79-4
98-5
85-2
74-6
95-2
78-7
77-6
91-7
98-5
88-3
68-9
860
pots.
Actual
N
(g m -)
%dry
%N
in green in dry
1600
14-60
15-20
15-75
Not determined
JJ
1700
*!
17-30
14-78
19-44
19-39
19-20
}»
3-50
2-44
2-44
2-43
0-150
0-413
0-438
0-407
Average of three pots.
Dry
weight
(gm-)
15-41
1502
15-63
17-41
17-97
17-32
Actual
%cU7
%N
N
in green
19-41
2013
19-86
18-99
18-24
20-14
in dry
1-99
200
2-10
2-73
2-56
2-53
(gm-)
0-307
0-300
0-328
0-475
0-459
0-438
On the heavier Rothamsted soil the plants were strong and well
developed, those not receiving a dressing of full artificials being somewhat
smaller than the rest. At no stage was any benefit apparent from the use
47-2
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724
Action of Certain Metallic Compounds on Crops
of either titanium fertiliser, and this was borne out by the figures obtained after harvesting, as shown in Table IX.
The dry weights of plants receiving only titanium fertilisers A or B
were practically the same as where no manure of any sort was applied,
and this also occurred where complete artificials were added to the
titanium fertilisers. The proportion of dry matter in green, the percentage
of nitrogen and the total nitrogen present all remained unaffected by thf
titanium fertilisers, both in the presence and absence of other artificials.
There was thus an entire lack of response to the added titanium on the
two soils tested with mustard, and no further opportunity has arisen of
testing other soils and crops with a wider range of dressings with titanium
compounds.
ALUMINIUM.
Aluminium has of recent years attracted a great deal of attention
because of its relation to problems of soil acidity, and much has been
written on the subject. It is not proposed to discuss this matter, but
attention must be drawn to the work of Hardy (19), Line (24), Magistad(28)
and others in this connection.
From the physiological point of view the interest lies in the part
aluminium may play in plant nutrition, and in its possible toxic or
stimulating action upon growth. It is not surprising that an element so
abundant in all soils should prove to be a frequent constituent of plant
tissues. Towards the end of last century many workers were active in
determining the presence of aluminium in various plant species.
Church(12) noted the occurrence of aluminium in certain cryptogams, as
much as 33-5 per cent, being found in the ash of Lycopodium alpinum.
Dunnington(i5) determined its presence in various weeds, including
Verbascum thapsus with 1-15 per cent., and Rumex obtusifolius with
045 per cent. A12O3 in the ash. Ricciardi (35), after estimating the
aluminium content of various plants, concluded that the assimilation of
alumina does not depend upon the percentage in the soil, and that
generally speaking it is most abundant in the trunk and branches, less
plentiful in the seeds and least abundant in the leaves. He expressed his
belief that alumina occurs in the most assimilable condition in soils that
are not very calcareous, such as clay soils, whereas on chalky soils it is in
a less available state. Ricciardi's record as to the distribution of
aluminium in plant tissues was corroborated later by Berthelot and
Andre(4), who reported that alumina is present in considerable quantity
in plants with extensive root systems (alfalfa roots 0-127-05 per cent.,
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WINIFRED E. BRENCHLEY
725
convolvulus roots 0-0596-0-4 per cent., Bermuda grass 0-011-0-12 per
cent.), but that it remains largely in the roots and is found only in
minute quantities in the leaves (lupin leaves 0-013-0-037 per cent.,
linden leaves 0-0012-0-0025 per cent.).
Many of the earlier records of the occurrence of aluminium in plants
were summarised by Langworthy and Austen (23), who gave a list of
authors and their chief results. The majority of plants contain only small
amounts of aluminium, usually below 1 per cent, of ash, with certain
noteworthy exceptions. Sayre(39) reported 11-13 per cent, of ash in the
root of Taraxacum, 18-07 per cent, of this being A12O3. Smith (41) found
abnormal quantities in Orites excelsa R.Br. (Proteaceae), in which
aluminium appears to be an inorganic constituent necessary for growth,
any excess being deposited in the cavities and naturalfissuresof the wood
as basic aluminium succinate. Normal specimens of the tree contain
35-45 per cent. A12O3 in the ash, but the tendency is for still more to be
absorbed, up to 80 per cent, on occasions when conditions are suitable for
• the deposition of aluminium succinate.
Methods for the microchemical detection of aluminium in plant
tissues were revised by Kratzmann(2i), who examined 130 plants,
corroborating the wider distribution of the element in the plant kingdom.
Many cryptogams show accumulation of alumina in the sporophylls,
while it tends to be concentrated in the blossoms of phanerogams.
Stoklasa(45) also put together much of the available information as to the
distribution and function of aluminium in the plant world.
It is outside the scope of the present paper to attempt to summarise
the work done on the harmful effect of aluminium compounds on plants
growing under ordinary soil conditions, but attention may be drawn to a
few references which indicate the type of results obtained (ii, 20,25). It is
desired rather to follow up the idea that aluminium may also be a
stimulating agent or even an essential nutritive element.
Stoklasa (44) indicated that generally speaking very small amounts of
aluminium salts benefit seed germination, larger amounts being toxic.
The action appears to vary with the species, as Varvaro (48) found that
aluminium oxide has a retarding effect upon the germination of beans
but acts as an accelerator of this process in maize. This is of interest in
that a few years later Maz6 (29) claimed that small quantities of aluminium
were necessary for the optimum development of maize, in common with
such elements as boron, fluorine and iodine. The same species, as well as
Viciafaba, Lens esculenta and Helianthus annuus, was improved by salts
of aluminium of 0-0001 per cent, concentration, though growth was
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726
Action of Certain Metallic Compounds on Crops
hindered by 0-005 per cent. (Kratzmann (22)). Sommer(42) suggests that
aluminium may be essential to millet, as in controlled experiments
growth was markedly improved in its presence, peas also showing a small
increase in total dry weight and a certain improvement in seed production. The question of the toxicity of aluminium is complicated by its
correlation with the acidity of the nutrient medium. Increasing concentrations of aluminium salts added to culture solutions tend to bring about
slight but progressive increases in the H-ion concentrations of the
solutions, due to hydrolysis of the aluminium salts. In any particular
case, therefore, it is necessary to be aware of the effect of varying H-ion
concentrations before estimating the effect of aluminium on growth. The
general consensus of opinion appears to be that aluminium exerts a toxic
influence on its own account, quite apart from its effect upon the acidity
of the nutrient solutions. Barnette(3) claimed that 0-5 mg. or more per litre
of aluminium supplied as nitrate, sulphate or chloride, was harmful to the
growth of wheat seedlings, causing decrease in dry weight, and that little,
if any, of the deleterious action was due to increased H-ion concentration.
Similar conclusions were reached by Conner and Sears (13), with barley,
who also found that the poisoning effect was reduced if much phosphate
was present. They attributed the toxicity of acid soils for many plants to
the presence of easily soluble aluminium salts. A parallel problem was
attacked later by McLean and Gilbert (26,27) who again demonstrated the
harmful action of aluminium when in contact with barley roots, even
when presented in a non-diffusible colloidal form. The lower toxic limit
was about 16 parts aluminium per million, but soluble phosphate in
equivalent concentrations completely counteracted the toxicity, while
from 3 to 13 parts of aluminium per million acted as a stimulant to
growth.
Pineapples appear to be less susceptible to aluminium poisoning
(Sideris(40)), being uninjured by nutrient solutions containing 25 parts
per million of the element, larger amounts being tolerated in soil, since
when soluble aluminium salts are added to soil the greater part of the
aluminium is removed from the solution. Spencer (43) studied the relation
between aluminium and acidity in sand cultures with Rhododendron
ponticum L., young seedlings potted in white quartz sand being supplied
with constantly renewed nutrient solution, and he found that in general
the toxic action of aluminium decreased as the acidity of the solution
increased. At JJH 5-5 aluminium was toxic even at a concentration of
1 part per million, whereas at j?H 3-0 a very noticeable stimulating effect
occurred with 3 parts per million.
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WINIFRED E. BRENCHLEY
727
Little information is available as to the physiological action underlying the toxicity or stimulation of aluminium. With Aspergillus niger
and Penicillium glaucum Zehl(52) found that the poisonous effect of many
compounds, including aluminium sulphate, increased with rise of temperature, the toxicity rising much more rapidly than the temperature.
No definite cause for this action was ascertained, as Zehl did not think it
was wholly explained by the increased ionisation of the salts at the higher
temperatures. Water plants as Spirogyra, Elodea and Lemna exhibited
reduction of starch in the presence of aluminium compounds, assimilation
being checked but not entirely inhibited, a certain amount of plasmolysis
occurring as well. Fluxi (16) believed that the aluminium salts act on the
diastases, thus partly accounting for the reduction in starch, and that
if grape sugar or glycerin is added to culture containing aluminium
compounds, the injurious action of the latter is prevented.
At Rothamsted, aluminium was one of a series of elements examined
for their possible stimulating action on plants grown in water cultures,
barley, peas and maize being grown.
Barley.
Preliminary tests (March 6-April 21), were made with potash alum
(AL,(SO4)3 + K2SO4 + 24H2O), which proved definitely toxic in concentrations from 1:1000 to 1:100,000, but showed no indications of
benefiting growth in lesser quantities down to 1:100,000,000. This was
inconclusive, owing to the second variable of potash in the alum, and
later tests were made with aluminium sulphate, providing aluminium to
correspond in quantity to that in the potash alum test. This provided a
set of cultures with aluminium sulphate ranging from 0-733:1000 to
0-733 : 100,000,000. The first trial, from March 19 to May 11, gave results
corresponding to those with potash alum, though the plants were larger,
owing to the more favourable growing season. The strongest concentration, 0-733 :1000, was again fatal to development, and was omitted from
the main series set up later.
Three sets of Plumage barley were started on April 23, in one of which
the nutrient solution remained unchanged throughout the experiment,
which concluded on June 16. In the two other sets the solution was
renewed every two and three weeks respectively for the same period. All
the experimental plants were taken from the same batch of seedlings,
sown April 14, the seeds being graded between 0-05 and 0-06 gm. During
the eight weeks of the experiment the differences between corresponding
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728
Action of Certain Metallic Compounds on Crops
plants in the three sets were not usually very marked, except that in the
unchanged series etiolation became evident and had to be rectified to the
provision of additional ferric chloride. The controls were all satisfactory,
the strongest being those in solutions with a three-weekly change, and the
weakest with a fortnightly change (Fig. 7).
gm
7
IS
\
6
5
i
i -
V.
3
2 -
I
\
\
1_
ti
1
h
1
c
i
d
1
e
i
f
Fig. 7. Total dry weights of barley grown in nutrient solutions with aluminium sulphate,
Solutions never changed;
solutions changed every 2 weeks.
April 23-June 16.
solutions changed every three weeks.
a, Control; no aluminium sulphate
b, 0-733: 100,000,000 aluminium sulphate
c, 0-733 : 10,000,000
d, 0-733 : 1,000,000
e, 0-733 : 100,000
/, 0-733:10,000
With 0-733 : 10,000 aluminium sulphate roots and shoots were badly
checked, the shoots remaining small and much etiolated throughout,
while the roots were short and bunchy, remaining above the surface of
the solution for some time and then pushing out some longer, thick
rootlets differing in type from the normal roots. The damage was
obviously more severe where the solution had been renewed, doubtless
owing to the additional supply of fresh toxic material brought into contact with the roots. This was further shown by the dry weights, which were
considerably reduced by change of solution. With lower concentrations
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WINIFRED E. BRENCHLEY
729
of aluminium sulphate the general impression was that most of the
plants were better than the controls, especially as regards the shoots.
This, however, was not borne out by the dry weights, which were in some
cases definitely lower than those of the controls, especially in the unchanged set. Statistical examination of the results by analysis of variance
showed no evidence of stimulation by any concentration of aluminium
sulphate, even when due allowance was made for a somewhat improved
growth of the controls owing to reduction of competition by their position
alongside small, badly poisoned plants. Toxic action was very evident
with 0-733:100,000 in the unchanged set, was less marked when the
solutions were changed every three weeks, and was hardly manifest with
a fortnightly change. The best general growth, however, was obtained with
a three-weekly change.
The result with the weakest concentration in the unchanged set was
inexplicably low, otherwise the results from all three series fall into line
when the standard error is taken into consideration, showing reduction
of toxicity to a neutral concentration varying with the frequency of
change of solution, but with no evidence of stimulation by any concentration down to 0-733 :100,000,000 aluminium sulphate.
Peas.
Sutton's Harbinger, from seeds graded 0-3-0-35 gm. was grown from
May 15 to June 28 in concentrations parallel to those of the barley
described above, only the unchanged series being tested. In this case
the strong 0-733 :1000 solution was interpolated, but the roots were most
seriously injured within three days, becoming white and flabby, and
gm.
2
1\
a
»
b
i
i
c
d
1
e
.
f
\
a
Kg. 8. Total dry weights of peas grown in nutrient solution with aluminium sulphate,
May 15-June 28. Solutions never changed.
a, Control; no aluminium sulphate
b, 0-733 :100,000,000 aluminium sulphate
c, 0-733 :10,000,000
d, 0-733: 1,000,000
e, 0-733: 100,000
/, 0-733:10,000
g, 0-733 : 1000
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730
Action of Certain Metallic Compounds on Crops
although a few abortive attempts were made to put out laterals above the
surface of the solution the plants were quite dead and shrivelled long
before the end of the experiment. In spite of the marked toxicity in this
case, however, the next concentration (one-tenth as strong) had no
adverse effect whatsoever, for although the plants looked as if they might
be a trifle weaker than the controls, the dry weights were fully as good.
Comparing this with barley under similar conditions it appears that peas
are less sensitive to the poisoning action of aluminium, as they are
unaffected by 0*733:10,000 aluminium sulphate, whereas barley is most
seriously checked by this and is also somewhat depressed by one-tenth
the concentration. With peas, also, there was not the slightest indication
of stimulation during the early vegetative phase of growth, the dry
weights being remarkably level for all concentrations tested (Fig. 8).
Maize.
The question arose as to whether the composition of the nutrient
solution would influence the effect of aluminium sulphate on growth.
Three solutions were therefore tested in parallel, the supply of nitrogen
being the same in all solutions to avoid the second limiting factor which
Table X. Total dry weights of maize after eight weeks' growth.
Solution
Control
0-733 : 100,000,000
0-733 : 10,000,000
0-733 : 1,000,000
0-733 : 100,000
0-733 : 10,000
0-733 : 1000
A (gm.)
3-92
4-08
3-45
412
316
1-24
0-32
B (gm.)
3-97
310
2-85
317
2-58
2-68
0-29
C (gm.)
3-83
3-34
3-79
401
4-31
1-87
0-29
might be introduced by deficiency of this essential element. The same
concentrations of aluminium sulphate were used as with peas and barley.
Maize was used as the test plant grown from seed, and the solutions were
changed once, for every solution, at the end of four weeks' growth. The
experiment was concluded when the plants were two months old.
Solution
Sodium nitrate
Potassium nitrate
Magnesium sulphate
Sodium chloride
Potassium di-hydrogen phosphate
Calcium sulphate
Ferric chloride
Distilled water to make up 1 litre
pE.
A (gm.)
—
10
0-5
0-5
0-5
0-5
004
B (gm.)
0-5
0-2
01
01
01
01
004
C (gm.)
—
10
0-25
0-04
0-25
0-25
0-04
3-5
31
3-5
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WINIFRED E. BRENCHLEY
731
In spite of the acidity of the solutions the plants grew well, except in
the strongest aluminium sulphate. 0-733 :1000 allowed practically no
growth, 0-733 :10,000 was markedly toxic in all three solutions, but the
toxicity of lower concentrations was doubtful, as the individual plant
varied so much in development (Table X). The hydrogen-ion concentration of the solutions were as follows:
Aluminium sulphate. Nutrient solution
Control
0-733 : 100,000,000
0-733 : 10,000,000
0-733 : 1,000,000
0-733 : 100,000
0-733 : 10,000
0-733 : 1000
A
3-5
3-5
3-5
3-5
3-3
31
pH below 3 1
B
30
30
30
30
30
30
below 3 0
C
3-5
3-5
3-5
3-5
3-5
31
below 3-1*
* Most acid of all solutions.
The very toxic action of the strong aluminium sulphate would not
appear to be associated with increased acidity, as in solution B controls
grew well in a solution as acid as those which killed the plants in the
presence of strong aluminium sulphate. It was rather surprising too that
as good growth of the controls was obtained in the acid solution B as in
the less acid A and C. With maize, as with peas and barley, no evidence
of stimulation was found with any concentration of aluminium sulphate
tested.
SUMMARY.
1. No beneficial effect on the growth of barley or mustard on two
types of soil was obtained by the addition of quantities of copper sulphate
ranging up to 4 per cent, of the total artificial fertilisers applied.
Experiments on English acid and alkaline peats with barley, rye and
turnips failed to show the striking results obtained by American workers
on saw-grass peat in the Everglades of Florida.
2. Increased fineness of grinding of basic slag in some cases brings
about a certain reduction of crop. This may be due to the presence of
vanadium in such slags, as experiments show that this element is
definitely toxic to plant growth.
3. Lithium compounds are much less toxic than copper to the growth
of barley. In some water culture experiments a suggestion of stimulation
was obtained with very dilute concentrations of lithium chloride in the
presence of nutrient salts, paralleling Voelcker's results with other
lithium compounds in soil. Buckwheat is much more sensitive to the
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732
Action of Certain Metallic Compounds on Crops
toxic action of lithium, and also shows no stimulation with any concentration.
4. Small proportions of titanium compounds, added to the usual
artificial fertilisers, failed to improve the growth of mustard on two very
different soils. The amount of lime present in the titanium compounds
was insufficient to act beneficially on that soil for which dressings of lime
were requisite in the ordinary course of cultivation.
5. Barley proved to be very sensitive to the toxic action of aluminium
sulphate, the harmful effect becoming more evident when the nutrient
solutions were renewed, so that fresh supplies of poison were brought into
contact with the roots. Peas were much less affected, remaining quite
healthy in concentrations which killed barley. The toxic action did not
appear to be associated with increased acidity, as maize grew well in a
control solution as acid as those which killed the plant in the presence of
strong aluminium sulphate. No evidence of stimulation was obtained
with either barley, peas or maize with any strength of aluminium sulphate, however dilute.
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