Organic Farming | 2016 | Volume 2 | Issue 1 | Pages 17–20
DOI: 10.12924/of2016.02010017
ISSN: 2297–6485
Organic
Farming
Research Article
An Experimental Test of a Biodynamic Method of Weed
Suppression: The Biodynamic Seed Peppers
Bruce K. Kirchoff
Department of Biology, University of North Carolina at Greensboro Greensboro, NC, USA. E-Mail: [email protected];
Tel.: +1 3363344953; Fax: +1 3363345839
Submitted: 16 February 2016 | In revised form: 14 April 2016 | Accepted: 15 April 2016 |
Published: 27 April 2016
Abstract:
An experimental test of a biodynamic agriculture method of weed suppression was carried out in
growth chambers to establish the feasibility of the method as a preliminary to field trials. Four generations
of Brassica rapa plants were used in a randomized block design. Treated flats received ashed seeds
prepared according to biodynamic indications. Seed weight and counts were measured at the end of
each generation, and germination of the control and experimental seed was investigated at the end of
generation four. The biodynamic seed peppers, created and applied as described here, had no effect on
seed production or viability, and did not effectively inhibit reproduction of the targeted species over the
course of four consecutive treatments.
Keywords: Biodynamics; biodynamic agriculture; weeds; invasive plants
1. Introduction
Invasive plants (weeds) create serious ecological problems
in both agricultural and natural systems. With each introduc-
tion the risks of detrimental effects increase. The intruders
usually lack natural enemies to control their proliferation,
often grow quickly, and can become major pests [
1
]. These
conditions have necessitated the development of methods
for removing or controlling the invasive plant. Unfortunately,
invasive species control is costly, often involves the use of
chemicals, and is often not appropriate for use in natural
areas [
2
,
3
]. Under these conditions it is worthwhile to inves-
tigate alternative methods of invasive plant control, even if
they are unconventional.
There are five currently accepted methods of weed con-
trol [
3
]: mechanical removal or destruction; prescribed fire;
grazing; biological control; and the use of herbicides. These
methods can be used alone or in combination, and are
intended to produce a maximum effect on a targeted weed
while minimizing harmful effects to the landscape. All but
the last of these are acceptable organic practices. Unfortu-
nately, all five approaches contain some risk of damaging
habitats in which they are used, and all lack complete effi-
cacy.
The damage caused by invasive species is massive.
The annual damage has been estimated at U$33 billion,
out of a total crop agricultural production of approximately
U$267 billion in the United States [
4
]. Clearly, safe, efficient
and cost effective methods for controlling or eradicating
invasive species are badly needed.
In 1924 the founder of the first organic system of agri-
culture, Rudolf Steiner, proposed a method of weed control
as part of his system of biodynamic agriculture [
5
]. This
method uses an ash prepared from the seeds of the weed
that is to be controlled, a “pepper”, that is spread over the
affected area. Steiner asserted that this treatment, when
properly prepared to take advantage of the forces of the
moon, will eradicate the treated species after four years
c
2016 by the authors; licensee Librello, Switzerland. This open access article was published
under a Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
librello
of applications. Although there are numerous anecdotal
reports on the efficacy of this method [
6
] (Grant Lyon, Jon
Lyerly, Hugh Courtney, personal communications), there
have been no peer-reviewed tests of its efficacy.
Steiner’s method for controlling a weed infestation is
relatively simple. One collects the seeds of the weed and
burns them over a wood fire at the proper moon phase.
The resulting ash is then scattered over the affected area.
Steiner claims that after two years of treatments there will
be a noticeable reduction in the population of the weed.
After four years of treatments the weed will cease to inhabit
the treated area [
5
]. In order to test these claims we inves-
tigated Steiner’s method of weed control under controlled
growth chamber conditions, and measured its effects on
seed production and seed viability over four generations.
2. Methods and Materials
Four generations of Brassica rapa L. plants [
7
] were grown
under continuous light at 22
◦
C in controlled environmen-
tal chambers (Environmental Growth Chambers, model:
GCW15) at the University of North Carolina at Greensboro.
Brassica rapa was chosen because it has a life cycle of
approximately 45 days under continuous light, and because
its seeds are retained within the fruit at maturity. Many
weeds spontaneously release their seeds making it difficult
or impossible to determine the reproductive output of the
plant. Seeds were obtained from Carolina Biological Supply
Company (Wisconsin Fast Plants, standard rapid cycling),
and the Rapid Cycling Brassica Collection in Maddison,
WI (www.fastplants.org; standard rapid cycling, RCI). We
used four consecutive generations of the experiment to sim-
ulate the four years Steiner claimed would be effective in
eradicating the weed.
Following Steiner’s indications, we created the seed pep-
per by burning the seeds over a wood fire within 24 hours of
the full moon (i.e., during the early waning moon) [
5
]. As the
pepper was mixed with wood ash as a result of the combus-
tion process, a second wood fire with no added seeds was
used to create control replicates of untreated ash. The two
fires were burned side by side, at the same time. The ashed
seeds and wood ash were crushed to a powder using a
mortar and pestle, and the resulting pepper and control ash
were weighed and divided into equal packets to be spread
over the flats.
The experimental apparatus consisted of twenty perfo-
rated half-flats (35.6
×
35.6 cm), 10 for the control group
and 10 for the experimental group. Each flat was filled with
approximately 3 L of Fafard 3b soil mix (Conrad Fafard Inc.,
U.S.). Thirty seeds were planted in each flat, two per hole,
approximately 3mm below the soil surface.
Each flat was randomly assigned to either the control or
treatment group. The 10 experimental flats were dusted with
equal amounts of the seed pepper at the beginning of each
generation, while the 10 control flats were treated with equal
amounts of wood ash at the same time. All 20 flats were
placed in growth chambers in a randomized block design.
Soon after germination each flat was thinned to contain only
fifteen seedlings, one per hole. For the length of the ex-
periment the flats were watered through a reservoir system.
Each flat received 1 L of water every other day. In order to
assure continued plant health in the nutrient poor soil mix,
generations 3 and 4 were fertilized once a week with Peter’s
20–20–20 general purpose water soluble fertilizer (Scott’s
Co. LLC., U.S.). The fertilizer was mixed at a dilution of 0.24
L of fertilizer to 94.6 L of water. One liter of the fertilizer
mixture was substituted for water every 7 days.
Brassica rapa requires cross pollination to set seed [
8
].
The pollen is sticky, and not easily susceptible to being car-
ried by the wind [
8
]. Under field conditions outcrossing is
accomplished primarily by physical contact between neigh-
boring plants, presumably due to plant swaying [
8
]. In our
growth chambers the flats were placed approximately 15
cm apart to minimize contact between plants in different
flats. Pollination was accomplished by using bee-sticks,
dehydrated bee thoraxes glued to the ends of small sticks
(www.fastplants.org). Individual bee-sticks were assembled
for each flat, and used only for pollinating within that flat.
This restricted pollen flow to each flat. Plants were polli-
nated over a five day period beginning on day 17 of each
growth period.
On day 35, watering was discontinued and the plants
were left undisturbed for one week to allow for the matura-
tion of the seeds. At the end of the maturation period, seeds
from each flat were harvested and kept separate. Seeds
produced from a particular flat were used to plant the next
generation of the experiment in that same flat.
For all but the second generation, the seeds from each
half-flat were weighed in aggregate. In generation two,
which produced few seeds, the number of seeds per flat
was counted directly.
To assess differences in mean seed production in each
generation, one-tailed t-tests under the assumption of equal
variances were performed with SPSS version 19 or 22
[
9
,
10
]. One-tailed tests were used because Steiner’s hy-
pothesis predicts lower seed numbers/weights following
treatment with the seed peppers. The t-tests for genera-
tions one, three and four compared mean seed weights
per treatment, while in generation two the number of seeds
produced between the control and experimental groups was
compared.
We also checked for differences in percent germination
between the control and experimental groups using the
seeds produced from the final generation.
3. Results
There was no significant difference between seed set in the
control and experimental groups in any of the four gener-
ations (Table 1). Germination rates were not significantly
different between seeds of the two treatments after four gen-
erations (Table 2). In all cases, Levene’s Test for Equality of
Variances was not significant. In generations two and four the
control group produced fewer seeds than the experimental.
18
Table 1.
Four generations biodynamic seed pepper treat-
ments.
Gen. Treatment Seed number Seed weight p-value 95% CI
(mean ± SE) (g; mean ± SE)
1 Control 2.44 ± 0.44 0.46 −0.44; 0.49
1 Experimental 2.42 ± 0.55
2 Control 43.9 ± 8.5 0.46 −50.85; 46.05
2 Experimental 46.3 ± 21.5
3 Control 11.0 ± 2.0 0.23 −3.14; 6.7
3 Experimental 9.22 ± 1.22
4 Control 2.08 ± 0.20 0.15 −0.81; 0.26
4 Experimental 2.35 ± 0.15
(Gen.: generation; SE: standard error; CI: confidence interval)
Table 2. Germination rates after four generations.
Treatment Number seeds germinated p-value
(± SE; out of 30)
Control 22.70 ± 1.34 0.11
Experimental 24.70 ± 0.86
(SE: standard error)
4. Discussion
Under the conditions detailed here we observed no de-
crease in seed viability or production in B. rapa with treat-
ment with a biodynamic seed pepper.
We attribute the low seed production of generation two
to the exhaustion of nutrients from the already nutrient-poor
potting soil. The addition of fertilizer at the beginning of
generation three restored normal yields.
The fact that the control group in generation four showed
lower seed production (2.08 g versus 2.35 g), and had a
lower germination rate (22.7/30 versus 24.7/30 seeds) than
the experimental group is contrary to Steiner’s prediction,
though these results are not statistically significant.
Prior to carrying out this work, we performed prelim-
inary experiments to test the effect of Biodynamic seed
peppers on seed germination of okra seeds (Abelmoschus
esculentus L. Moench) [
11
,
12
]. These experiments yielded
negative results after three generations of treatments. An
experiment testing the effects of a biodynamic pepper pre-
pared from the burned skin of the brushtail possum (Tri-
chosurus vulpecula Kerr ) in New Zealand also gave nega-
tive results [
13
]. Similar negative results were obtained by
B
¨
achi-Kunz using a BD pepper to control the Red Flower
Beetle (Tribolium castaneum Herbst) [14].
The most extensive series of experiments with the bio-
dynamic seed peppers was performed in Germany over a
seventeen year period, but the results were never published
outside a little known conference proceeding [
15
], which was
unknown to us until after we completed our experiments.
Spieß tested the seed peppers on dandelions (Taraxacum
officinale F.H. Wigg.) and other agricultural weeds growing in
open fields, and in a variety of containers. The effects of the
peppers on seed germination were also investigated. Biody-
namic agricultural practices were used throughout these trials.
In the field experiments, various preparations of the peppers
were spread annually on the experimental fields, while no
treatment was applied to the control fields. Three separate
types of ash preparations were used on separate experimen-
tal plots: ash prepared at the full moon, ash prepared at
the new moon, and ash prepared to a homeopathic potency
of D8 following the suggestion of Thun [
16
]. Results of the
treatments were measured as the number of dandelion inflo-
rescences produced per square meter (Figure 1). Negative
results were observed during the first four years, in which the
number of inflorescences in the control group was consistently
less than those of the experimental group. In the remaining
thirteen years, Spieß observed only four years in which the
control groups showed a higher number of inflorescences
than the experimental groups (1988, 1993, 1995, 1999) but
there was no consistent pattern of inflorescence production
between the control and experimental groups, or even within
the experimental treatments themselves. All groups had simi-
lar low production in some years and similar high production
in others, regardless of treatment regime (Figure 1).
These results, and those reported here, will undoubtedly
evoke debate within the biodynamic community over how
the ash was prepared, and the susceptibility of Steiner’s
methods to experimental verification, though Spieß’ exten-
sive work using a variety of preparation methods on estab-
lished biodynamic fields should mitigate these criticisms.
Some critics will undoubtedly claim that Steiner’s methods
are effective, but cannot be verified in controlled experi-
ments. These claims are in direct contradiction to Steiner’s
own expectations that his methods should, and would be
verified experimentally [5].
In terms of ash preparation, Thun [
16
] has suggested
that effective preparation should take both lunar position
and zodiacal sign into consideration. She goes so far as
to suggest that the moon’s position in the zodiac is specific
for a given species of weed, whose seed should only be
burned when the moon is in that constellation. She also rec-
ommends that the ash be prepared in specific homeopathic
potencies for effective use. Steiner’s original presentation
Figure 1.
Results of a 17 year study (data was not collected
for the first two years) on Taraxacum officinale occurrence
after application of a BD seed pepper. Asterisks (*) indicate
treatment/years where there was a significant difference in
yield at the 0.5 level (Modified after [
15
], with permission).
19
of his method gives no specific recommendation on either
the position of the moon in the zodiac, or in fact of any
astrologically beneficial configuration for burning the seeds
[
5
]. His published method is clearly and simply stated. The
farmer is to gather the seeds, burn them and spread the ash
“taking no special care to do so”. In handwritten notes for the
lecture in which he proposed this method, Steiner did give
an indication of a favorable lunar position, burning during
a waning moon. These notes were published in English in
the 1993 edition of his Agriculture Course, which was used
as the source for our methods [
5
]. Recommendations on
zodiacal positions and homeopathic potencies arise from
Thun’s own research, which has not been peer reviewed
[
16
]. We find Thun’s recommendations implausible, given
that Steiner’s much simpler method has failed to yield posi-
tive results, and given Spieß’ failure to achieve results using
homeopathically prepared peppers (Figure 1) [15].
Acknowledgements
I thank Melanie Eldridge for conducting these experiments
and writing an early draft of this manuscript, in partial ful-
fillment of the requirements for an independent research
course at the University of North Carolina at Greensboro. I
regret that Melanie could not be contacted to grant consent
to be a co-author of this paper.
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