biodynamic and
conventional
farming systems: A
review
John P. Reganold
|
Abstract. Biodynamic and organic farming are similar in that both are ecologically oriented and do not use chemical fertilizers and pesticides. The main difference is that biodynamic farmers add eight specific amendments, called preparations, to their soils, crops, and composts. Recently, there has been an increasing interest in biodynamic farming practices and systems because they show potential for mitigating some detrimental effects of chemical-dependent conventional agriculture. Only a few studies examining biodynamic methods or comparing biodynamic farming with other farming systems have been published in the referred scientific literature, especially in English. This paper summarizes data from previous studies, both published and unpublished (theses), that have compared biodynamic and conventional farming systems with respect to soil quality or profitability. These studies have shown that the biodynamic farming systems generally have better soil quality, lower crop yields, and equal or higher net returns per hectare than their conventional counterparts. Two studies that included organic management treatments with and without the preparations showed that the preparations improved biological soil properties and increased crop root growth. However, more research is needed to determine whether the preparations affect soil physical, chemical, and biological properties and crop growth and, if so, their mode of action. |
Growing concerns about the environ-mental, economic and social effects of chemical-dependent conventional agriculture have led many farmers and consumers to seek alternative practices and systems that will make agriculture more sustainable. Alter-native farming systems include ‘organic’, ‘biological’, ‘biodynamic’, ‘ecological’, and ‘low input’. How-ever, just because a farm is “organic” or ‘Biodynamic,’ for example, does not mean that it is sustainable. To be sustainable, it must produce food of high quality, be environmentally safe, protect the soil, and be profitable and socially just (Reganold et al., 1990).
Recently, there has been increasing interest in
biodynamic farming and gardening. For example, between 1989 and 1992 the number
of biodynamic farms in
Biodynamics is considered by some to be the oldest
organized alternative agriculture movement in the world. It began in 1924 following a series of
lectures by Rudolf Steiner, the founder of anthroposophy, at the request of
German farmers (Koepf, 1989). Within a
few years, interest spread to several European countries. Ehrenfried Pfeiffer brought bio-dynamics to
the
Like organic farming, biodynamic farming uses no
synthetic chemical fertilizers and pesticides, and instead emphasizes building
up the soil with compost additions and animal and green manures, controlling
pests naturally, rotating crops, and diversifying crops and livestock. A major difference is that biodynamic farmers
add eight specific preparations to their soils, crops, and composts to enhance
soil and crop quality and to stimulate the composting process (Koepf et al, 1976.)
The eight preparations, designated by their ingredients
or by the numbers 500 to 507, are made from cow manure, silica, flowers of
yarrow, chamomile, dandelion and valerian, oak bark, and the whole plant of
stinging nettle (Table 1). Some
biodynamic farmers make the preparations themselves while others buy them from
certifying biodynamic associations or experienced practitioners.
The thoughts behind the preparations are unconventional and based on a holistic approach to nature. When applied, extracts of the preparations are so highly diluted in water that physical or biological effects seem unlikely. Yet significant increases in yield have been reported in the biodynamic literature (Goldstein,1990).Biodynamic practitioners maintain that the preparations are not ‘witchcraft’, ‘snake oils’, ‘miracle cure-alls’, or part of a get-rich-quick scheme. Goldstein (1990) believes that people who doubt that the preparations benefit agriculture do so for the following reasons:
· Most people have probably not heard of biodynamics or biodynamic preparations.
· Biodynamics is based on spiritual-physical principles. Spiritual matters are difficult, if not impossible, to measure.
· The making of the preparations seems strange or unsanitary to many.
· Such small amounts of the preparations are applied to crops, soils, or compost that a response seems unlikely.
· No correct chemical/physical answer to why the preparations may work has been offered. Some have proposed that the preparations act as microbial inoculates; others, think they may have hormonal effects or maybe even radiative effects.
Besides the preparations, there are other differences
between organic and biodynamic farming.
Modern organic farming was started by Sir Albert Howard in
Although there have been many articles, ranging from the
sketchy to the detailed, describing studies of biodynamic practices, most of
this information has not been reviewed according to rigorous scientific
principles by traditional soil scientists, agronomists, or agricultural
economists (Koepf, 1993). Few studies
examining biodynamic farming methods or comparing biodynamic with other farming
systems have been published in the referenced scientific literature, especially
in English. Most such studies have been
conducted and published in
This paper summarizes data from several previous
investigations comparing biodynamic and conventional farms or research plots in
Europe,
Table 1. The
eight biodynamic preparations, which consist of fermented materials that wre
used as field sprays or in manure or compost piles (Proctor, 1989).1
Preparation |
Substance from which preparation is produced |
Application of preparation |
|
500 |
Cow manure fermented in a cow horn |
A spray for soils before planting |
|
501 |
Silica fermented in a cow horn |
A spray for growing crops |
|
502 |
Flower heads from yarrol (Achillea millefolium)
fermented in the bladder of a stag |
Preparations 502 through 507 are applied to manure
or compost piles |
|
503 |
Flower heads from German chamomile (Matricaria
recutita) fermented in a cow intestine |
|
|
504 |
Stinging nettle (Urtica dioica) fermented
in the soil |
|
|
505 |
Oak bark (Quercus robur; in fermented in the skull of a domestic animal |
|
|
506 |
Flower heads of dandelion (Taraxacum officinale)
fermented in a cow mesentry |
|
|
507 |
Juice pressed from valerian flowers (Valeriana officinalis) |
|
1 Although not considered one of the eight main
preparations, a ninth preparation, sometimes referred to as 508,is made by
boiling the horsetail
plant (Equisetum arvense) and is applied only in excessively wet years
to prevent fungal diseases.
Volume 10, Number 1 1995
High quality soils not only promote the growth of plants, but also prevent water and air pollution by resisting erosion and by degrading and immobilizing agricultural chemicals, organic wastes, and other potential pollutants. The quality of a soil is determined by a combination of physical, chemical, and biological properties such as the soil’s texture, depth, porosity, capacity to store water and nutrients, organic matter content, and biological activity (National Research Council, 1993). In this section I report on studies examining different combinations of soil physical, chemical and biological properties of farms or research plots under biodynamic and conventional manage-ment. Some studies also include an organic treatment.
|
Table
2. The eight treatments in the field plot
experiment in | |
|
Treatment |
Fertilizer Application |
|
K1 |
Compost manure with biodynamic preparations 502
through 507 and, from 1962 on, 1% levels of meat meal and bone meal (only bone
meal after 1974); soils and plants treated with biodynamic preparations 500 and
501, respectively. |
|
K2 |
Same
as K1 but excluding biodynamic sprays 500 and 501 |
|
K3 |
Raw
manure with 1% additions of horn and bone meal as of 1974 |
|
K4 |
Raw
manure at half the K3 rate plus inorganic MPK fertilizer at half the K6 NPK
rate |
|
K5 |
Control
(unfertilized) |
|
K6 |
Organic
NPK: From 1958 through 1973, compounded from Ca(NO3 )2,
NH4NO3 , superphosphate, and K2SO4
; from 1974 on, prepared blend (11-5-18) with trace minerals |
|
K7 |
Inorganic
NPK at twice the level as in K6 |
|
K8 |
Inorganic NPK at four times the N level and twice the P and K levels as in K6 |
In all three sampling years, the topsoil of the biodynamically treated and organically fertilized plots (K1-K4) generally was higher in organic matter, microbial activity, enzyme activity (dehydrogenase and urease), earthworm channel, total N, and pH than the topsoil of the control (K5) or chemically fertilized plots (K6-K8) (Pettersson et al., 1992). Among the organically fertilized treatments (K1-K4), treatment K4, the only one with both organic and inorganic fertilizers, had the lowest microbial activity, dehydrogenase activity, and earthworm channels for all three years. Extractable P levels were highest in the chemically fertilized treatments (K7 and K8) in all three years.
In the Pettersson et al. study (1992), average yields for all four crops over the 32 year period (1958-1989) were comparable for all treatments, except that the control (K5) was lower and the low NPK treatment (K6) somewhat lower. The variation in yield among the seven treatments other than the control was almost 20%, with the K8 treatment (high NPK) having the highest average yield and the K6 treatment (low NPK) the lowest.
Granstedt (1991) measured plant nutrient inputs and
outputs on conventional and biodynamic farms in
In another plot study on an
experiment station in German, Reinken (1986) found higher organic matter levels
and earthworm populations on biodynamically treated vegetable and apple plots
than on conventionally treated vegetable and apple plots.
Austrialia. In a comparison of a
biodynamic and an adjacent conventional farm in
Forman also conducted a greenhouse pot trial with
wheat using soil samples from the biodynamic paddock and the conventional
paddock. Both soils received various
combinations of two biodynamic preparations (500 and 507) and two inorganic
fertilizer nutrients (N and P). A total
of 16 treatments (including a control), each replicated three times, was
applied to pots from both biodynamic and conventional soils. Over all treatments, Forman found that the
biodynamic soil had higher wheat seedling emergence counts 7 and 8 days after
sowing and a much higher rate of tiller
formation 13 days after
sowing than the conventional soil (Table 3). It also had significantly higher dry matter
wheat yields (48 days after sowing), and higher yields per unit of water added
(water use efficiency) than the conventional soil. Plants grown in the biodynamic soil had a
significantly higher N content and uptake, P uptake, and Ca content than plants
grown in the conventional soil, but P content was significantly higher in the conventional
soil.
Table 3. Mean values of soils data
from adjacent paddocks and plant data from pot trials,
|
Soil1 and Plant Properties |
Biodynamic Farm |
Conventional Farm |
|
Soil Properties in Field Study |
|
|
|
C(%) |
1.43* |
0.94 |
|
Total Nitrogen (%)2,3 |
0.23 |
0.13 |
|
Extractable P (mg/kg) |
44.9* |
27.8 |
|
Extractable Mg (cmol/kg) |
1.65 |
1.86* |
|
Extractible K (cmol/kg) |
1.33 |
1.39 |
|
Extractable Na (cmol/kg) |
2.17 |
4.63* |
|
pH |
6.12* |
5.57 |
|
|
|
|
|
|
|
|
Pot Study |
|
|
|
Seedling emergence count (7 days after
sowing)3 |
111 |
48 |
|
Seedling emergence count (8 days after
sowing)3 |
210 |
165 |
|
Plants showing tiller development (13
days after sowing)3 |
86 |
13 |
|
Mass of dry matter wheat produced (g)
per pot (48 days after sowing) |
2.57* |
1.57 |
|
Mass of dry matter wheat produced per
amount of water added (mg/ml) |
1.32* |
0.98 |
|
Plant N content (%) |
2.09* |
1.84 |
|
Plant N uptake (mg) |
55.2* |
30.4 |
|
Plant P content (%) |
0.36 |
0.46* |
|
Plant P uptake (mg) |
9.4* |
6.9 |
|
Plant Ca content (%) |
0.33* |
0.25 |
|
Plant K content (%) |
3.31 |
3.17 |
|
Plant Mg content (%) |
0.13 |
0.12 |
*Indicates a significantly higher value (p<0.01, usig a two-sided t-test
for the field study ad a two-way ANOVA in a randomized complete
block design for the pot study).
1Based on a sampling depth of 0-10 cm.
2Total N means are each based on analysis of only two
bulked samples per paddock; all other soil properties are averages for 25
3Not statistically analyzed.
Volume 10, Number 1, 1995
Penfield (1993, 1994)
established a long-term research project in 1989 at the Roseworthy Campus of
the university of Adelaide in Australia to investigate soil characteristics,
crop yields, and economics of four farming systems: biodynamic, conventional, integrated (low
input), and organic. The systems are
being compared in a 16 ha campus farm paddock previously in pasture, with two
replicated 2-ha plots per treatment. A
wheat crop is grown in all treatments every four years. After four years, the four treatments showed
few statistically significant differences in organic C, VA mycorrhizae,
microbial biomass and activity, earthworms, water infiltration, soil erosion,
or extractable P (Penfold, 1994).
The physical condition of
the soils on all 16 farms has since been assessed (Reganold and Palmer, unpublished
data) using a soil structure index developed by Peerlkamp (1967), as modified
by McLaren and Cameron (1990).
Reganold et al. (1993)
analyzed only the vegetable farm pair for earthworms and found the
biodynamically cropped soil to have more than 8 times as many earthworms (more
than 25 times by mass) as the conventionally cropped soil. In later measurements on two of the other
farm pairs in the study of Reganold et al. (1993), Levick (1992) found 12 times
as many earthworms on the biodynamic citrus farm and 84 times as many earthworms
on the biodynamic pipfruit farm compared with their conventional
counterparts. Levick also found that the
biodynamically farmed soils had significantly higher water infiltration rates,
porosity, organic C and soil respiration, and lower bulk density ad penetration
resistance than the conventionally farmed soils.
Table 4. Mean values of aggregated
soils data (Reganold et al. 1993).
|
Soil Property1 |
All Biodynamic Farms |
All Conventional Farms |
|
Bulk
density (Mg/m3) |
1.07 |
1.15* |
|
Penetration resistance (0-20 cm) (MPa) |
2.84 |
3.18* |
|
Penetration
ressistance (20-40 cm) (MPa) |
3.55 |
3.52 |
|
Soil
Structure Index2 |
7.4* |
5.7 |
|
Topsoil
thickness (cm) (includes surface and subsurface (A) horizons |
22.8* |
20.6 |
|
C (%) |
4.84* |
4.27 |
|
Respiration
(mL O2
h-1 g-1) |
73.7* |
55.4 |
|
Mineralizable
nitrogen (mg/kg) |
140.0* |
105.9 |
|
Ratio of
mineralizable N to C (mg min N/g C) |
2.99* |
2.59 |
|
Cation
exchange capacity (cmol/kg) |
21.5* |
19.6 |
|
Total N (mg/kg) |
4840* |
4260 |
|
Total P
(mg/kg) |
1560 |
1640 |
|
Extractable P (mg/kg) |
45.7 |
66.2* |
|
Extractable S (mg/kg) |
10.5 |
21.5* |
|
Extractable Ca (cmol/kg) |
12.8 |
13.5 |
|
Extractable Mg (cmol/kg) |
1.71 |
1.68 |
|
Extractable
K (cmol/kg) |
0.97 |
1.00 |
|
pH |
6.10* |
6.29* |
* Indicates a significantly higher value (p<0.01, using a two-way ANOVA).
1 Based on a sampling depth of 0-10 cm, except where noted.
2 Unpublished data (Reganold and Palmer, 1994) based on soil structure
index developed by Peerlkamp (1967), as modified by McLaren and
Researchers in the studies reported here used enterprise gross margin as a measure of economic performance, except for Vereijken (1986; 1990). Gross margin is the difference between gross revenue and variable or operating expenses. Variable costs include fertilizers, pesticides, fuels, labor, and biodynamic preparations, among others. Fixed costs such as debt servicing were excluded.
The yields of all the cereal crops on biodynamic
farms for 1979/1980 and 1980/1981 were lower by 13%; the average being almost
equal to conventional farm yields on the good soils and considerably lower on
the poorer soils. Koepf (1986) points
out that part of this difference may have been due to preference of
biodynamic farmers and
their customers for certain lower yielding cultivars with
desired baking qualities, and to the production of spelt (Triticum spelta,
or German wheat), hulless oats, and hulless barley for human consumption. Potato yields were similar in the two farming
systems. Milk yields per cow on
biodynamic farms were almost 15% lower than on the conventional farms. Again, Koepf (1986) notes that this
difference may have resulted because biodynamic farmers who wished to qualify
for Demeter (biodynamic) certification were allowed to buy commercial feeds
only up to 10% of the dry matter content of the ration.
The costs and returns for the biodynamic and
conventional farms in the Schlüter study are shown in Table 5. The biodynamic and conventional farms had
similar gross revenues Gross revenues in
German marks (DM) per ha from all crops were higher on the biodynamic farms,
whereas gross revenues from animal husbandry (beef, pork, milk and eggs) were
25 to 54% lower on the biodynamic farms (Koepf, 1986). However, because the biodynamic farmers had
lower costs than the conventional farmers, their profits were higher (Table
5). In the two years studied, biodynamic
products received an average premium of 59% (range 15 to108%) over the price of
similar conventional products (Koepf, 1986).
On research plots at an experiment station in
German, yields of all vegetable crops for a six-year period averaged 16% less
on biodynamic plots than on conventional plots (Reinken, 1986). However, since the prices received were
higher for biodynamic than for conventional vegetables, profits were
significantly higher for most biodynamic vegetables, including spinach, celery,
red beet, white cabbage, and carrot.
Table 5. Gross revenue, expenses, and
profits of biodynamic and conventional farms in
Farm size: |
10-20 ha |
20-30 ha |
30-40 ha |
|||
|
|
Bio |
Con |
Bio |
Con |
Bio |
Con |
|
Number of farms |
4 |
928 |
4 |
1,689 |
4 |
1,612 |
|
Average size of farms (ha) |
17.7 |
16.2 |
22.1 |
25.0 |
38.4 |
37.6 |
|
Gross revenue (DM ha-1yr-1) |
6,369 |
6,625 |
6,874 |
5,774 |
3,507 |
4,689 |
|
Expenses
(DM ha-1yr-1) |
3,934 |
5,093 |
3,713 |
4,505 |
2,415 |
3755 |
|
Profit (DM ha-1yr-1) |
2,435 |
1,532 |
3,161 |
1,269 |
1,092 |
934 |
Volume 10, Number 1, 1995
Reinken (1986) found that average yields of three
varieties of apples for the six-year period were 30 to 38% lower on the
biodynamic plots than on the conventional plots. Profitability for apples was not
reported. Labor requirements for apple
growing were an average of 27% higher on the biodynamic plots, but the
biodynamic apples received a premium of 27% over the price of conventional
apples.
An early study by the Baden- Württemberg Ministry of
Food, Agriculture and Environment in
The
These results contrast sharply with other results
discussed in this paper. As pointed out
by Lampkin (1990), a major flaw in the Nagele study is that the biodynamic unit
was established as a labor-intensive mixed dairy and arable system (11-year
crop rotation) in an area that is almost exclusively arable. The conventional and integrated units were
set up as arable farms with the same four-year crop rotation. Labor costs for the biodynamic farm were
almost three times higher than for either the conventional or integrated farm,
causing most of the
difference in net
returns.
Lampkin (1990) concludes that a less labor intensive
organic system could have been developed that would have been more competitive
given the conditions in the region.
Table 6. Rotations (1989-1992), wheat
yields (1992), and gross revenue, variable costs, and gross margin (1989-1992)
of biodynamic, conventional, integrated, and organic plots in
|
|
Biodynamic |
Conventional |
Integrated |
Organic |
|
Rotation: 1989 |
oats/medic
for hay |
wheat |
oats/medic
for hay |
oats/medic
for hay |
|
1990 |
legume-based
pasture |
peas |
legume-based
pasture |
wheat
(mulched) |
|
1991 |
oats/vetch
for hay |
legume-based
pasture |
legume-based
pasture |
green
manure crop |
|
1992 |
wheat |
wheat |
wheat |
wheat |
|
|
|
|
|
|
|
Wheat
yield (1992)
(t/ha) |
2.3 |
3.5 |
2.7 |
2.9 |
|
|
|
|
|
|
|
Total
over rotation 1989-1992 (A$/ha) |
|
|
|
|
|
Gross revenue |
1,399 |
1,196 |
823 |
992 |
|
Variable costs |
391 |
436 |
553 |
352 |
|
Gross
margin |
1,008 |
760 |
270 |
635 |
On a per hectare basis the biodynamic farms were as profitable as the
neighboring conventional farms and re representative conventional farms (Table
7). Most of their products were sold as
certified organic or biodynamic at premium prices up to 25% above the market
prices of similar conventional products.
Most of the biodynamic farms had less year-to-year variability in gross
revenue than the conventional farms (Reganold et al., 1993). Economic stability is a significant
characteristic of sustainable farming systems.
|
Table
7. Average annual gross revenue, variable costs,
and gross margin of biodynamic and conventional farms in New Zealand, 1988 to
1991 (Reganold et al., 1993). | |||
|
Average (NZ$ ha-1 yr-1) |
|||
|
Farm enterprise |
Bio |
Con |
MAF1 |
|
Market
gardens |
|
|
|
| Citrus Orchards Gross revenue Variable costs Gross margin |
|
|
|
| Mixed Farms Gross revenue Variable costs Gross margin |
|
|
|
| Livestock Farms Gross revenue Variable costs Gross margin |
|
|
|
| Dairy Farm Set #1 Gross revenue Variable costs Gross margin |
|
|
|
| Dairy Farm Set #2 Gross revenue Variable costs Gross margin |
|
|
|
|
1 Representative conventional
farm based on New Zealand Ministry of Agriculture and Fisheries. 2
There are
no MAF models for market gardens. 3
Only two
years of financial data were available, so averages are not reported here. 4
Economic
records were not available. Volume
10, Number 1, 1995 |
|||
The farming goals of biodynamic practitioners
include protection and enhancement of soil to produce high quality
products. To stimulate life in the soil
and in plants, they use eight specific amendments, called preparations, on
their soils and crops and in their composts.
Their system includes practices such as green and animal manuring,
composting, biological pest controls, reduced tillage, complex crop rotations,
and diversified crops and livestock.
This paper has summarized the few studies available
in English that have compared soil quality or farm profitability in biodynamic
and conventional farming systems. These
studies found that the biodynamic farming systems generally had better soil
quality, lower crop yields, and equal or greater net returns per hectare than
their conventional counterparts. The
economic studies showed that biodynamic farming systems can and do work. Many biodynamic farmers stay in business
because of the price premium received for their products. Although the studies reported here included
these premiums, they did not count the environmental and health costs of the
two farming systems, which are external to the farm’s accounts. The log-term profitability of many
conventional farms seems questionable when these externalities are
included. Indirect costs such as offsite
damage from soil erosion, surface and ground water pollution, hazards to human
and animal health, and damage to wildlife from conventional farming practices
are presently borne by society. When
these external costs are included in the costs of production, the profitability
and benefits to society have been shown to be
the greater for some alternative farming systems (Holmes, 1993).
Some of the studies on soil quality were conducted
on a single pair or multiple pairs of commercial farms. Conducting paired-farm research to compare
the effects of agricultural systems on soil requires three things: 1)
neighboring farms that are now managed by different systems but that previously
were under similar management; 2) side-by-side fields where soil-forming
factors are equalized; and 3) sufficient time for each management system’s
respective practices to have influenced soil properties (Reganold, 1988;
Reganold et al., 1993). Pseudoreplication,
where replicates are not statistically independent, in the strictest sense is
unavoidable when comparing two fields form a single farm pair, as in the Forman
(1981) study. As Hurlbert (1984, p.199)
explains: “Replication is often impossible or undesirable when very large-scale
systems (whole lakes, watersheds, rivers, etc.) are studied. When gross effects of a treatment are
anticipated, or when only a rough estimate of effect is required, or when the
cost of replication is very great, experiments involving unreplicated
treatments may also be the only or best option.” The commercial farms in the studies discussed
here meet the criteria or large-scale systems.
Still, when possible, it is better to use multiple farm pairs in a block
design to have proper replication. How
statistical difficulties in farming systems comparisons can be overcome through
proper design and analysis is discussed by Wardle (1994) and Reganold (1994).
Plot studies, too need adequate replication for
proper statistical design. For example,
the plot studies by Penfold (1993) and by Pettersson and von Wistinghausen
(1979) would have been improved if they had four replicates per treatment
instead of two and one, respectively.
Yet these studies still are valuable, because they demonstrate different
farming systems and provide long-term results.
An interesting question raised by the soil studies
is whether soil quality is affected by the biodynamic preparations in
particular, or whether the effects are from the organic amendments applied in
the biodynamic system The research of
Goldstein (1989) and Abele (1987), which included siilar organic farming
treatments with and without the preparations, illustrate that the biodynamic
preparations positively influence biological soil properties and crop root
growth. Much work on the preparations
has been done by biodynamic researchers.
The results have been variable, particularly regarding the effect of the
preparations on manure decomposition, soil biology, crop yields, and the keeping
quality of different products (Goldstein, 1990). However, very little has been published in
the refereed scientific literature and not all the work was of high scientific
quality. More research is needed that
specifically examines whether the biodynamic preparations affect the soil’s
physical, chemical, and biological properties and crop yield and quality, and
if so, their mode of action. The results
of such studies need to be published in refereed scientific journals.
Acknowledgement: Part of this paper was presented at
the 3rd Wye International Conference on Sustainable Agriculture and
appeared in the conference proceedings “Soil Management in Sustainable
Agriculture” (H. Cook and H>C> Lee, eds., University of London, Wye
College, Wye, England, 1994).
References
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2. Bio-Dynamic Farming and Gardening
Association in
3. Foissner, W. 1987. The microedaphonin ecofarmed and
conventionally farmed dryland cornfields near
4. Forman, T. 1981. An introductory study of the bio-dynamic
method of agriculture. Diploma Thesis.
5. Garcia, C., C.E. Alvarez, A. Carracedo, and
E. Iglesias. 1989. Soil fertility and mineral nutrition of a biodynamic avocado
plantation in
6. Goldstein, W.A. 1986. Alternative crops,
rotations and management systems for the Palouse Ph.D. dissertation. Dept. of Agronomy and Soils, Washington State
Univ.,
7. Goldstein, W. 1990. Experimental proof for
the effects of biodynamic preparations. Internal manuscript. Michael Fields
Agric. Institute, East troy,
8. Granstedt, A. 1991. The potential for
Swedish farms to eliminate the use of artificial fertilizers. Amer. J.
Alternative Agric. 6:122-131.
9. Holmes, B. 1993. Can sustainable farming
win the battle of the bottom line? Science 260:1893-1895.
10. Hurlbert,
S.H. 1984. Pseudoreplication and the design of ecological field
experiments. Ecological Monographs
54:187-211.
11. Koepf, H.H. 1986. Organisation, economic
performance and labour requirements on bio-dynamic farms. Star and Furrow
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12. Koepf, H.H. 1989. The Biodynamic Farm.
Anthroposophic Press,
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John P. Reganold is Professor, Department of Crop
and Soil Sciences,
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