Evaluating a Range of the Benefits and Costs of
Organic and Conventional Production in
a Clare Valley Vineyard in South Australia
S.A. Wheeler1 and P. Crisp2
1.
Centre for Regulation and Market Analysis, University of South Australia, GPO Box 2471, Adelaide
SA 5001, Australia. [email protected].
2.
South Australian Research and Development Institute, GPO Box 397, SA 5001, Australia.
[email protected]
December 2009
Paper for the pre-AARES conference workshop on The World’s Wine Markets by 2030: Terroir, Climate
Change, R&D and Globalization, Adelaide Convention Centre, Adelaide, South Australia, 7-9 February 2010.
EVALUATING A RANGE OF THE BENEFITS AND COSTS OF ORGANIC AND
CONVENTIONAL PRODUCTION IN A CLARE VALLEY VINEYARD IN SOUTH
AUSTRALIA
S.A. WHEELER1 and P. CRISP2
1.
Centre for Regulation and Market Analysis, University of South Australia, GPO Box 2471,
Adelaide SA 5001, Australia. [email protected]. (Designated Speaker)
2.
South Australian Research and Development Institute, GPO Box 397, SA 5001, Australia.
[email protected]
Abstract
This study compares and contrasts a range of economic, environmental and social data on yields, grape
quality, variable costs, worker benefits, soil carbon and biodiversity of organic and conventional
viticultural production in the same estate in Clare Valley, South Australia. Comparisons are made
between overall farming system averages, red and white grape variety averages to individual grape
variety averages, and strong evidence over a number of years was found for: (i) an overall yield penalty
per hectare for organic blocks of around 10 per cent but no yield penalty between similar grape
varieties; (ii) an overall cost penalty per hectare for organic blocks of around 20 per cent; and (iii) an
overall higher grade quality for organic red grape varieties but a lower overall grade quality for white
grape varieties. There was limited evidence from one year to suggest that there were higher soil
arthropod and mite populations in the organic blocks and no difference in soil organic carbon between
systems. In addition, there was strong evidence of positive externality influences on surrounding
conventional management. Studies of long-term industry comparisons of organic and conventional
viticulture are rare, and there has been little published comparison of the two systems in Australia.
Keywords: organic viticulture, conventional viticulture, yields, economics.
EVALUATING A RANGE OF THE BENEFITS AND COSTS OF ORGANIC AND
CONVENTIONAL PRODUCTION IN A CLARE VALLEY VINEYARD IN SOUTH
AUSTRALIA
Introduction
Viticulture in Australia has previously been criticised for causing environmental problems through soil
erosion, land degradation, spray drift, wastewater from wineries, reduced biodiversity. Such problems
have led to the development and application of Environmental Best Practices for regions and a national
strategy to improve the image of the wine industry and its relationship with the environment (WFA
2002).
Growing consumer concern over some agricultural production methods and a demand for products that
they perceive as cleaner and greener has lead to an increased demand for organic products in Australia
(Organic Research Centre 2008). Similarly, increasing pest and disease resistance to agricultural
chemicals (such as Botrytis fungicides on vines) and disruption of biological control systems (e.g.
increasing secondary pest mite problems on vines due to use of broad-spectrum insecticides) has
encouraged farmers to move towards different farming techniques (Madge 2005, Crisp et al. 2006).
Farmer surveys indicate that around a quarter would like to learn more about organic viticulture and
feel that they do not have enough information (Madge 2005). As at 2006, it was estimated that there
were 12.3 million hectares of organic agricultural land, representing 2.8% of total farmland, with 1,550
farms (Willer et al. 2008). In 2007, it was estimated that the organic fruit and wine market was valued
at over $34 million, with certified organic grapes and wine worth around $2 million (Organic Research
Centre 2008).
Despite the growing importance of organic viticulture in Australia, there is only one comparative study
published on organic and conventional viticulture (Madge 2005), with only a few known
internationally (Organic Farming Research Foundation 1996, Willer & Meier 2000, Plahutaa & Raspor
2007, Desta, 2008). Niccolucci et al. (2008) found that the ecological footprint of an organically
produced Italian Tuscan wine was lower than its conventional counterpart. Madge (2005) compared 2
conventional and 5 organic viticulture farms and found that organic yields were 29-44 per cent lower
and organic variable costs were 15 per cent lower to 47 per cent higher. These results are higher than
what has been found elsewhere, although the methodology used for comparisons in this study is not
considered to be best practice so the results should be considered with caution. On average, Australian
studies have found lower yields for organic farming in developed countries (e.g., Wynen 2001,
Dumaresq & Greene 2001), however Badgley et al. (2007) compared 293 examples of yields of
2
organic versus conventional or low-intensive food production and found little difference between the
average yields in the developed world. In general, there is more yield variability experienced in
cereals, and less difference experienced for fodder, horticultural crops and livestock.
Overall, studies have found that organic farms have lower overall input costs (e.g., Wynen 2006), with
Offerman and Nieberg’s (2000) review estimating that organic farms have approximately 20% lower
overall input costs (driven primarily by lower fertiliser, chemical, energy and fixed costs, albeit they
have higher labour costs). Madge (2005) found lower disease and weed management and harvesting
variable costs for organic viticulture farms than conventional farms, though pruning variable costs were
considerably higher. Because of the lower input costs and price premiums received, studies usually find
organic farms have similar or higher financial returns (Wynen 1988, Lampkin & Padel 1994,
Offermann & Nieberg 2000). If price premiums are not received (it is estimated that in Australia 35%
of produce from certified organic farms are sold conventionally (Halpin 2005)), then organic farms
generally have lower financial returns.
The extensive literature on the food quality differences between organic and conventional produce
provides some evidence overall that organic produce is of a higher quality. In particular, the empirical
evidence suggests organics offers less contaminant levels in its food (e.g., Baker et al., 2002); higher
levels of ascorbic acid (e.g., Magkos et al., 2003); higher levels of plant secondary metabolites (e.g.,
Birzele et al., 2002, Brandt et al., 2004, 2006); higher antioxidants (e.g., Benbrook, 2005); increased
phenolic metabolites (e.g., Brandt et al., 2004, 2006, Tarozzi et al., 2006); and lower levels of nitrate
(e.g., Woese et al., 1997).
Survey evidence suggests that organic farmers find their farm work to be more satisfying than
conventional farmers (Rickson et al., 1999), while Trewavas (2004) argues that the work on an organic
farm is harder and more back-breaking that work on a conventional farm, hence labouring on an
organic farm is unlikely to be preferred to labouring on a conventional farm.
Studies usually find that in comparison with conventional farming, organics clearly demonstrates
increased species abundance and richness across a number of different areas, especially for species that
have suffered declines (e.g. Kasperczyk & Knickel, 2006). Organic farming has been shown to have
higher microbial activity, biomass and diversity (i.e., Hole et al. 2005), greater conservation of soil
fertility and system stability and structure (i.e., Wells et al., 2000) and increased soil organic carbon
content (i.e. Drinkwater et al. 1998, Pimental et al. 2005).
Methods
We used data from a commercial company in South-Eastern Australia.
In the early 1990s, the
company decided to convert some of its production to organic agriculture (certified with NASAA).
The main reason for this choice was a marketing decision; it was thought it may help to improve the
image of the company and hence increase sales. A site in Clare Valley was chosen as the site most
3
suitable in South Australia for organic conversion, given its climate, hardy soils and low disease
problems.
There are a range of methodologies employed in evaluating differences between organic and
conventional farming, and each has its own advantages and disadvantages.
Although long-term
scientific experiments in the US and Europe have collected long-term data, they have been primarily
designed as scientific experiments. Our data is commercial, with the company’s main goal to manage
both its conventional and organic fields to achieve an economic profit. The current research provides
some unique advantages over other comparisons of systems, such as:
•
We have a range of high-quality time-series of data, with some data series starting in the 1980s,
and the problem of fully accounting for and valuing farm household labour is not present;
•
The same management manages both the organic and conventional fields. Managerial influences
are often named as the biggest non-system determined factor in evaluating differences between
conventional and organic farms, with organic farmers often suggested to be the better managers
and hence it is not the farming system that provides the differences, it is the farmer;
•
Estate characteristics (in terms of technology available, marketing factors, labour available etc) are
the same;
•
Location characteristics of the blocks compared are similar, as they are located in the same climate
area, rainfall zone, soil type, topography and altitude to a large extent;
•
The collection of data from the conversion stage onwards allows some comparison of the changes
that occurred in the organic fields;
•
Conventional and organic viticultural produce is one of the few agricultural products that is
evaluated solely on some forms of its product quality and assigned a price. As at 2006, there was
no price premium paid for the organic grapes because they were certified organic. Grapes were
assessed solely on the same grade quality level that applied to all conventional grapes.
It is important to keep in mind that the analysis is not a pure comparison of conventional and organic
farming systems; nor were they designed as a scientific trial (and as such, data on factors such as soil
analysis, pesticide residues, biodiversity changes, water changes etc are limited). Not all vineyards
were planted at the same time, hence allowances must be made for a grapevine to be fully productive in
the analysis; and data are not fully available for all years for all blocks for the aspects evaluated, and
were stored in a number of different computer systems. In addition, the company has changed the
databases used to store data a number of times since the 1980s, making historical data collection
difficult.
Nevertheless, the commercial data provides a unique comparison analysis of conventional and organic
farming viticulture systems in terms of: yields; variable costs; grape quality and financial returns. It
also provides some information on soil arthropods; soil organic carbon and general worker satisfaction.
4
Only relatively simple internal comparisons have been conducted on the data by the company
previously (Macnamara 2003).
Site Details
As at 2006, the estate was made up of ten blocks with 219 hectares of vineyards. Comparisons were
made in this study between two organic and four conventional blocks. 23.79 hectares of land was
converted in 1990 to organic with certification achieved in 1992. A further 28.19 hectares were
converted to organics in 1994 with conversion fully achieved by 1997. In 2002-03, a further 19.92
hectares of land were converted (this block was not studied given that it was only planted in 1998). As
at 2006, the two organic blocks represented 51.39 hectares, and the four conventional blocks
represented 75.24 hectares (the share of the organic area is 41%). The principal organic and
conventional wine varieties were cabernet, chardonnay, merlot and shiraz.
When the land was initially converted in the early 1990s, the lack of knowledge and information that
management had about organic farming meant that they were organic more by ‘default’ or ‘neglect’
rather than a true ‘holistic organic’ style. That is, they could be described more as low input systems
than organic systems. This changed by the middle of the 1990s, when new management arrived and
attempted to implement more complete organic strategies. More changes to the management of the
organic fields occurred after visiting organic agricultural professors from Europe suggested
improvements in the 2000s. At the same time, as knowledge levels increased about how to farm
organically, management techniques in the conventional fields were changed.
Once the results
achievable in the organic fields were seen, insecticide application was eliminated in the conventional
fields.
This meant that rather than representing an average conventional viticultural farm, the
conventional fields in Clare Valley are managed more by a low input, environmentally friendly style.
Therefore, a comparison of the Clare Valley viticultural fields may not provide a truly accurate
comparison of an average conventional with an average organic vineyard. It is important to keep these
differences in mind when interpreting the results.
Yields and Variable Costs
Yield data was available from 1985 to 2006 for five blocks in the estate (with some varieties ending in
certain years and others beginning). One block had data from 1988 onwards. The average tonne per
hectare was calculated for all sections of blocks, and then was aggregated to provide organic and
conventional averages. Comparisons were made only between fully certified organic blocks and the
corresponding conventional blocks; hence data was used from a fifteen year period, from 1992 to 2006.
All vineyard blocks and years were included in the analysis, even those that had undergone
redevelopment (note – a range of sensitivity testing was conducted such as only including blocks that
had not been redeveloped and where differences were noted these have been commented upon). Eight
sections of blocks (32 in all) had gone through redevelopment in the time period analysed. Note, all
years for all blocks were also included, even when unnaturally heavy frosts disadvantaged the yield of
5
organic blocks given their location. Yield averages per ha by farming system, red and white variety and
by grape variety was calculated (with significance between systems tested using paired t-tests).
Variable input cost data was available from 1997 to 2005, and labour and non-labour variable cost
averages per ha by system, red and white variety and grape variety were calculated (with significance
between systems tested using paired t-tests). Variable costs do not include administration and other
Estate costs that are generic to all systems, and non-labour costs include material and contract costs.
Grape Quality
Data on the grade of output was available from 1998 to 2006. The grades only take into account brix
levels, titratable acidity, pH levels and minimum standards. They therefore do not take into
consideration food quality issues such as vitamins, mycotoxins, the absolute level pesticide residues,
etc., and as such, cannot be considered a complete analysis of grape quality.
Prior to 2002, grapes were assigned in the system either an A (i.e. best), B, C or D quality grade. From
2002 onwards, grapes were assigned an A3, A4, B1, B2, B3, C1, C2, C3, D1 or D2 grade. For
statistical comparison purposes, each code was assigned a number. 1 Average quality differences by
system, red and white variety and by grape variety were calculated (with significance between systems
tested using paired t-tests).
Environmental Factors
One conventional and two organically managed blocks of the estate were chosen as sample sites in
June 2006 to assess soil arthropod and mite populations. The size and diversity of the soil mite
populations are used as a guide to the structure, soil carbon and health of the soil. The soil mesofauna
appear essential in the maintenance of the populations and activity of microbial communities (Lavelle
1997) which maintain soil health and enhance nutrient uptake by plants. The mesostigmatid predatory
mites of South Australian horticultural soils are generalist feeders, and would be expected to benefit
from most conditions that boost the abundance of detrivores, fungae and other food sources in these
soils.
The conventionally managed block had not been cultivated in the past 6 months and no cover crop had
been planted. Weed management included the use of glyphosate herbicides. Cover crops, either faba
beans or triticale, had been planted in the organic blocks and the soil had been cultivated for weed
control prior to planting the cover crops. Soil-litter samples consisted of 20 trowel scrapes taken from
0-2.5cm depth and 2.5-5cm depth, each placed into 3.5 litre sealable plastic containers. 150 cc subsamples of each of these samples was then placed in a Berlese funnel (sealed 22cm diameter funnel
fitted with a 15 watt light globe) and left for a 72 hour extraction period. The extracted invertebrates
1
Where: D2=1, D1=2, C3=3, C2=4, C1=5, B3=6, B2=7, B1=8, A3=9, A4=10. The A to D
grades were then given averages of the above, such as: A=9.5, B=7, C=4, D=1.5. The higher
the number, the better the quality.
6
were collected in a specimen container containing 80% ethanol. Additionally soil samples were taken
from each site for calculation of the organic carbon levels in the soil at each site.
The soil-dwelling predatory mite data were analysed for site-to-site differences in abundance using
ANOVA, and for differences in diversity and richness using the Shannon-Weiner diversity index
(Southwood & Henderson 2000) and the species richness index d (where d=(S-1)/log N, and S = the
number of species and N = the number of individuals).
Worker Benefits
Verbal information on farm accidents from 1992 to 2006 was provided for the estate. To investigate
whether farm workers will prefer to work on the conventional vineyards than the organic vineyards, a
voluntary survey with a reply paid envelope was handed out to all permanent workers (i.e. not
contractors) on the estate (13 workers in all) in May 2006. The survey contained questions on their job
and work preferences, socio-demographic questions and whether they believed in the overall benefits
of organics. A reasonable response rate of 69% was achieved.
Results
Yield Results
Figure 1 provides an overview of the average tonne per hectare in the organic and conventional blocks
from 1992 to 2006. The line graph shows the organic yield as a percentage of conventional yields over
time. Over the period 1992 to 2006, on average, organic yields were 9% less than conventional yields
overall, though this difference was not significant (p=0.22). Over this same time period, red grape
organic yields were 15% less (p=0.15), and white grape organic yields were 5% less (p=0.50). If redevelopment blocks are excluded from the analysis, then the difference between organic and
conventional blocks becomes slightly larger (10% difference) and weakly significant (p=0.09).
Breaking the data down into grape varieties provides an even different picture. Comparisons were
made between CAS, SHI, MER and CHR by system. No significant yield differences were detected
from 1992 to 2006. Therefore, most of the yield differences are being driven by varieties that are grown
conventionally on the estate but are not grown organically. This may indicate that some conventional
varieties are unable to be grown organically, and these tend to have a yield advantage.
Although these results provide some support for the hypothesis that the yield per hectare from the
organic vineyards will be lower than the yield per hectare from the conventional vineyards, it also
confirms that adopting organic management in horticultural-based systems does not result in large yield
decreases, and is also dependent on the type of variety of plant. As is common in the years after
conversion the greatest difference in yield between conventional and organic production was 19921994 when the organic production system was not fully optimised.
7
INSERT Figure 1
Variable Cost Results
Variable input cost data was obtained from 1997 to 2005, and averages per ha by system, red and white
grape variety and individual grape varieties were calculated, as shown in Table 1.
INSERT Table 1
The hypothesis that the organic blocks will have lower overall input costs than the conventional blocks
is rejected strongly (p=0.00), with average input costs per hectare in the organic vineyards being
significantly higher than the average conventional costs per hectare. Such a result is driven by higher
labour input costs in the organic system, with very few significant differences found between the nonlabour costs of each system (even though the average non-labour cost of the organic systems was
relatively higher). On average, organic red grape varieties cost significantly more to produce than
conventional red grape varieties, while there was only a slight significant difference found between the
total costs of the organic and conventional white grape varieties (p=0.08). When the analysis is broken
down by individual grape variety, all organic varieties have significantly higher labour costs (with
organic SHI also having significantly higher non-labour costs), with the exception of organic CHR.
Grape Quality Results
The average grade quality received by the organic blocks from 1998-2006 was 4.74 while the average
conventional grade quality was 4.70 (no significant difference (p=0.75)). The average grade qualities
for organic red and white varieties was 5.6 and 3.6 respectively, while the average grade qualities for
conventional red and white varieties was 4.8 and 4.4 respectively (differences were both significant
(p=0.00 for red, p=0.04 for white). When quality is assessed by grape variety, organic CAS and MER
produce significantly higher quality grapes than their conventional counterparts (p=0.00 and 0.02
respectively), while organic SHI has a relatively higher grade quality but it is not significant (p=0.29).
Organic CHR is the only grape that has significantly lower grape quality than its conventional
counterpart (p=0.03), and these results, along with other white grape varieties, drive the overall results
for organic wine quality down. Hence, the hypothesis that organic grapes will be of higher quality than
conventional grapes is accepted for red varieties, but not for white varieties, with no difference detected
overall.
INSERT Figure 2
Environmental Results
In the upper soil samples, 0-2.5cm depth, the total populations of the selected species was significantly
greater in the organic block planted with faba beans and least in the conventionally managed block
(Table 2). The population pattern was consistent for all other functional groups measured except
predatory mites, where there was no significant difference in the populations from any of the blocks.
8
The populations in the soil samples taken from between 2.5 and 5cm depth were not significantly
different, except that the population of predatory mites in the organic block planted with faba beans
was greater than in the other soils.
INSERT Table 2
Soil carbon results are shown in Table 3. There were no significant differences in soil carbon data
between systems. Hence, these results can not explain the difference in mesofauna populations,
therefore one could argue that it is the organic management that is responsible for the differences in
populations.
INSERT Table 3
The data suggest that the soil under conventional management is less able to sustain mesofauna
compared to the soils under organic management, this may be due to a number of physical or chemical
factors. However, the lower mesofauna populations in the soil from the conventionally managed block
would limit nutrient recycling and increase the reliance of synthetic inputs which reduces the long term
sustainability of the block and increases the risk of runoff contamination of ground water and nearby
waterways. The low population of predatory mites is possibly due to the winter sampling when
populations of soil mesofauna, and predatory mites in particular are lower than in spring and summer.
Worker Benefit Results
Verbal information on farm accidents from 1992 was provided by the manager on the estate from 1992
to July 2006. The Estate had an outstanding safety record in this period (which is considerably
different to the rest of the industry) and as a consequence there were no farm accidents. Hence, there
was no statistical difference to be detected between the organic or conventional systems.
The majority of responses to the worker preference survey (7 in total) stated they had no overall system
preference. Two workers preferred to work on the conventional blocks, because it required less
physical labour and allowed for more control over weeds. Although no worker preferred to work on
the organic blocks, the preference difference between the two systems was not significant (p=0.17).
Overall, 44% of the workers believed in the net benefits of the organic system, with the remainder
believing that there was no difference, or that they did not know. Only one worker did not believe in
the net benefits of the organic system. There seemed to be no relationship between the workers’ work
preferences and their beliefs, although the workers who preferred to work on the conventional blocks
were slightly more likely to believe in the net benefits of the organic system (correlation = 0.60). Such
a result most likely highlights that there was no strategic answering by respondents, and that how they
feel about the organic system differs as to where they would prefer to work on the Estate. There were
only weak positive correlations between age and farm background. No respondent had experienced a
farm accident/incident hence this correlation could not be established. Hence, the hypothesis that farm
workers would prefer to work on the conventional blocks is rejected.
9
Discussion
Organic farming has often been strongly criticised for not being a sustainable form of farming for the
future because of its yield penalty and increased costs (Trewavas 2004). Although its environmental
credentials have been largely supported in the scientific literature, its food quality benefits have
remained a point of debate between many commentators. This study sought to investigate a range of
differences between organic and conventional farming systems using a unique set of company data
from 1992 to 2006. On the one hand, this company data provided an excellent basis for comparison of
systems because it eliminated problems that are often experienced such as manager skills, different
farm characteristics, different climate, limited trial years, and a clear food quality test on the produce
produced. On the other hand, the data still had its issues as each system may not have represented an
‘average organic viticulture farm’ or ‘an average conventional viticulture farm’. Indeed, one of the
greatest benefits of the estate implementing organic viticulture was the externality effect. As managers
eliminated insecticides and pesticides from the certified blocks, they realised that they did not need to
apply certain chemicals in the conventional blocks, and hence changed their practices elsewhere.
Knowledge and learning from the organic blocks resulted in positive environmental externalities as a
whole, and such is a strong benefit for organic viticulture that cannot be quantified. It also supports
results such as found by Lohr (2005) in her work on the spill-over effects of organic farming in the
USA. Lohr (2005) compared 36 economic, social and environmental indicators of counties with
organic farms with counties without organic farms. Counties with organic farms compared better on 26
out of 36 indicators, whereas counties without organic farms compared better on only three indicators
(seven were neutral).
These results suggest that organic farms are influencing the practices of
conventional farms around them, and indeed, the study here has found that this was the case on the
estate and for the surrounding suppliers of grapes.
There was little difference found between the yield of the organic blocks yield and the conventional
blocks. Although there was a relative yield differences found in favour of the conventional blocks
(around ten per cent) over the time period considered (1992 to 2006), it was only weakly significant
(and only applicable when re-development blocks were considered in the analysis). Indeed, the relative
difference in yields was driven solely by the fact that there were varieties only grown conventionally
that out-yielded the varieties only grown organically. When the yield comparison studied the actual
varieties grown in both systems, there were no yield differences found. This reinforces the fact that
farming organically results in different consequences for different industries, and it seems the yield
penalty in horticulture and viticulture systems is slight.
Costs were found to be higher in the organic system from 1997 to 2005, and were driven by higher
labour costs. Overall, costs were up to twenty per cent higher per hectare. On the other hand, over the
time period from 1998 to 2006, organic grapes had relatively higher grade quality, although this
10
difference was only significant for red grapes, while organic white grapes had significantly poorer
grade quality than conventional white grapes. Our evidence on environmental benefits was limited to
one year, though the hypothesis that organic blocks will have more biodiversity present than the
conventional vineyards was supported. There was no evidence found that the soil on the organic
blocks had greater soil organic carbon than the soil on the conventional blocks. Although a few estate
workers had a preference to work on the conventional blocks than the organic blocks, the difference
was not significant, and most workers believed in the net benefits of the organic system.
Conclusion
Overall, this study has found that there are a range of benefits and costs attached to organic viticulture,
as compared to conventional viticulture. There is some evidence that organics is a more sustainable
system and can produce higher quality produce, although this is far from conclusive from the data
available. Although yields are overall lower on the organic blocks, there was no significant yield
penalty when identical grape varieties were compared, which indicated the yield difference overall was
driven by the type of varieties grown conventionally that were not possible to grow organically on the
estate. The fall in average total organic yields are, on average, far less than what many have suggested
or what is considered average in other industries. Organic viticulture resulted in significant increases in
variable input costs which were driven primarily by higher labour costs. It is important to note that
different results were found for red and white grape varieties, and again for comparing actual grape
varieties themselves, indicating the problem in assuming similar effects of organic farming across
industries. Indeed, perhaps the most important benefit of the presence of organic farming on the estate
is that it created a positive externality effect in making the conventional management of other
viticultural blocks more sustainable for the long term. Even given the issues associated with the data
comparisons in this study, the results strongly suggest that further analysis on the outcomes of organic
viticulture in Australia will be needed to fully assess the differences between systems.
Acknowledgements
Data and assistance was provided by a variety of people from the commercial company in question,
namely: Andrew Holly, John Matz, Peter Hayes, Greg Pearce, Tim Brooks, Vikki Neldner, Greg
Colbert, John Peet, Janice Rowett, and workers at the Clare Valley Estate. We are also grateful for
advice received from Professor David Round.
11
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14
TABLES
Table 1 Average Variable Costs1 per Hectare ($) from 1997 to 2005
Labour
Non-Labour
3,841**
4,373
3,880
4,435
3,808***
4,321
OA CAS
3,544*
3,266
OA MER
3,906*
3,543
OA CHR
3,852
3,467
OA SHI
3,908*
3,520**
Conventional Average
3,487**
3,907
3,394
4,033
3,592***
3,766
CV CAS
3,287*
3,134
CV MER
3,229*
3,205
CV CHR
3,474
3,584
CV SHI
3,076*
3,172**
Organic Average
Organic White
Organic Red
Conventional White
Conventional Red
* P<0.05
** P<0.01
*** P<0.001
15
Table 2 Populations of selected soil mesofauna extracted from 100cc samples of soil, from three
blocks of Vitis vinifera at the Clare Valley Estate
Total
Cover crop
Total
Colembola
mites
mites
mites
Conventional
None
41
39.3
3.4
2.3
1.1
Organic
Triticale
81.1**
76.5**
5.8**
4.2*
1.6**
Organic
Faba beans
106**
98.5**
8.4**
7.4**
1
Conventional
None
15.5
14.5
2.7
2.2
0.5
Organic
Triticale
10.9
8.9
3.8
2.8
1
Organic
Faba beans
21.8
19.5
4.2
2.5
1.7**
Soil Depth Management
0-2.5cm
2.5-5cm
Detritivore Predatory
* P<0.05
** P<0.01
16
Table 3 Soil Carbon Results from three blocks of Vitis vinifera at the Clare Valley Estate
Soil Depth
Management
Cover crop
Soil Carbon (%)
0-2.5cm
Conventional
None
2.1
Organic
Triticale
2.0
Organic
Faba beans
1.9
Conventional
None
1.7
Organic
Triticale
1.8
Organic
Faba beans
1.9
2.5-5cm
17
160.00
Conventional
Tonnes per ha
14
OA as % of CV
140.00
12
120.00
10
100.00
Organic
8
80.00
6
60.00
4
40.00
2
20.00
0
0.00
%
16
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
18
16
14
Yield per ha
12
10
8
6
OA White
OA Red
CV White
CV Red
4
2
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
0
Figure 1 Average Yields in the Conventional and Organic Blocks, by system and red/white variety
18
7.00
Quality indicator
6.00
5.00
4.00
OA WHITE
3.00
CV WHITE
2.00
2006
2005
2004
2003
2002
2001
2000
1999
0.00
1998
1.00
8.00
Quality indicator
7.00
6.00
5.00
OA RED
4.00
CV RED
3.00
2.00
1.00
20
06
20
05
20
04
20
03
20
02
20
01
20
00
19
99
19
98
0.00
Figure 2 Average Grape Quality in the Conventional and Organic Blocks, by red/white variety
19