Sustainable Composting in the Vineyard

1. NOVEMBER/DECEMBER 2003
PART II
S U S TA I N A B L E
composting
BY Will Brinton & Alan York
IN THE VINEYARD
I
n France, what is known today as
traditional viticulture evolved
after thousands of years of trial
According to Richard Smart and John that are hard to quantify. These include
and error that created a basic
Gladstone, “Old World opinions — soil nutrient adsorption, water-holding
understanding of the nature of the
especially in France — strongly capacity, and biological disease sup-
plant and its relationship to a site (soil
emphasize soil effects. It is a principal pression traits.
and climate).
basis for the concept of terroir, which Wine grape culture defies, to a
A review of the soil characteristics
underlies the official French AOC sys- large extent, knowledge we have
of the world’s most recognized vine-
tem. New World opinion has tended to from common agronomic rules for
yards is very revealing in regard to soil
minimize the role of soil and instead to fertilization and attainment of yield
quality. This became the basis by which
stress major differences in regional and the approach taken to site-ori-
a system of classification was devel-
climate, or macroclimate.”20 ented production. Within the frame-
oped known as AOC (Appellation
Terroir may be grasped as “authentic work of wines for mass consumption,
d’Origine Contrôlée) in France. The
fertility” — the reliance principally on based on high-yielding grape vines,
AOC system evolved into a national
what the deep soil profile within a the agronomic model may have
reality in the 1930s as a result of vari-
landscape offers. An additional aspect, greater validity.
ous factors including economic depres-
which bridges tradition with the mod- A case where a positive trait of com-
sion, widespread cultivation of hybrids,
ern ecology of recycling, is that this post may be a negative in viticulture is
and uncontrolled wine blending.
local, site-specific quality is fostered by in the behavior of rootlets. Roots love
Presently, AOC regulations oversee
recycling of the vineyard’s own compost and may come to the surface
production areas, vine varieties,
residues and nutrients, supplemented if compost has been layered heavily on
ripeness and alcoholic strength, yields,
only to the extent needed (see Part I, the soil. The shock to the grapes comes
viticulture (vine density, pruning, vine
PWV Sept/Oct 2003) to make compost- later, under dry conditions, when these
training system, and irrigation), and
ing successful. roots cannot survive.
winemaking and distillation.
The question is: With an under- From years of experience, it has
Figure I: Average composition standing of the nature of the grape been found that heavy applications of
of finished compost and its traditional predilection for compost (more than 10 tons/acre) all
Microbial deep-soil, low-nutrient conditions, too easily encourage surface feeding. It
(Mineral Elements): Biomass how to best use and apply compost to would be better for vines to seek out
N-P-K-Ca-Mg-Fe- 0.6%
Al-Zn-Cu Stones, foster balanced vine growth? Can water and deeper layer minerals,
15.2% Sand,
Silt, Clay compost use be overdone? If so, how? which better fits the concept of soil and
Extractable 40.1%
Humic+Fulvic Visual indicators of excessive supply site-specific management.
Acids of nutrients are often the best refer-
5.6%
ences. Low input, site-specific
It is necessary to first examine what A significant body of evidence sup-
is referred to in modern terms as soil porting the concept of local soil qual-
quality. Soil quality is defined as the ity is seen in long-term fertility stud-
combined effects of biological, chemi- ies. In Leigh and Johnston’s work
Organic Matter / Plastic+Glass cal, and physical properties.1 Compost (1994), the basis of long-term soil pro-
Stable Humus (depending
on source) contributes indirectly and holistically ductivity is revealed by examining
37.1%
1.5% to this aggregate of soil quality in ways field research plots that have been run

2. 2 NOVEMBER/DECEMBER 2003
WINEGROWING
Table I: Choosing Compost Table II: Nutrient mineral composition of pomace composta
■ Make it yourself, if possible, IN COMPOST Organic Total- Potash Calcium Phosphorus
■ If you have to buy in compost, Matter Nitrogen (K) (Ca) (P)
consider asking the following:
• What are source ingredients? lbs/ ton as isb 460 23 28 27 5
• Has it been tested by a lab familiar Per 4 tons 1840 92 112 111 20
with compost? Per 10 tons 4600 230 280 278 50
• Is a sample available to examine?
(a) Compost prepared at Benziger Family Vineyards, Glen Ellen, CA. (b) Average of three batches.
■ You should also find out:
• Are grower reports on use of the
product available?
as mycorhizal relationships which the attainment of high yield, which
• Is the supply seasonal? How so?
are very common in grapes — aids a requires increased soil manipulation
plant’s ability to extract sufficient and inputs, and “sustainable yield,”
continuously for 150 years in nutrients for ongoing yields with sur- represented by lower yields and
Rothamsted, England.2 prisingly little inputs. These observa- fewer inputs but higher quality.
One finding is that conservative tions partly explain the success of However, there is no simple, single
additions of manure over decades sup- low-input viticulture. formula to strike a balance. For vine-
port soil improvements that persist long Low-input sustainable approaches yards, the low-input approach fits the
after the amendments are discontinued. need not be thought of as exclusive to site-specific scheme closely.
In contrast, long-term grass plots receiv- premium wines, as research will
ing no fertilizer stabilized at sustainable, attest. Comprehensive farm studies Compost, a balanced approach
low yields, with roots colonized to a in Austria support a “farm-organ- As pressure for sustainable prac-
considerable soil depth. The grasses ism” concept in general agriculture. tices and recycling increases, the bene-
were apparently drawing on the incalcu- There, researchers asked what factors fits of compost come more into focus.
lably large but only slightly available contributed most to quality and per- However, there is a danger in treating
reserves in the deep profile. formance of the farms. They gathered compost like a silver bullet. Benefits of
The work of Bordeaux researcher soil and crop data across four geo- compost should not be seen as isolated
Dr. G. Seguin provides an excellent graphical regions and correlated from but rather in addition to the
basis for appreciating the complex these with quality indicators. inherent qualities of the site and soils.
value of soils.5 He stresses that the best The results indicated that the As noted in Part I, the mandate to
soils for wine quality have the follow- more management moved a soil “reduce and recycle” does not auto-
ing characteristics: away from its typical natural state matically result in great soil amend-
• Moderately deep to deep; (such as with heavy liming, mineral ments.
• Fairly light-textured, often with balancing, and high nutrient inputs), Compost should be handled with
gravel through much of the profile the less satisfactory was the overall quality control practices, just as any
and at the surface; quality.3 This may be partly due to other agricultural product. The bene-
• Free draining; the well-known fact that over-liming fits must be viewed in context of rea-
• Sufficiently high in organic matter significantly reduces trace element sonable application rates related to
to give soil friability, a healthy availability. appropriate effort and costs involved,
worm population, and adequate While these studies are not specific to along with the expected outcome.
nutrient-holding capacity, but not, grapes, there is no reason to believe that Over-rating the benefits of compost
as a rule, particularly high in results in vineyards would be any differ- may serve the interests of the organic
organic matter; ent. John Reganold, working at community as a New York Times article,
• Relatively infertile overall, supply- Washington State University-Pullman, has “A Magic Organic Elixir” suggests.14
ing enough mineral elements for recently shown that apple flavor improves When sensational or panacea-like
healthy vine growth, but only with sustainable soil practices.22 The same attributes are assigned to an organic
enough nitrogen early in the season author, working in New Zealand, com- input, especially compost, consumers
to promote moderate vegetative pared paired groups of farms using con- and growers may be misled. Growers
vigor. ventional and biodynamic practices. The may adopt practices that are costly
The combination of all factors — latter group, with significantly fewer and don’t produce the benefits
the gradual and very slight natural inputs, had lower yields but scored higher expected. Or the benefits vary
weathering of soil minerals, deposi- on a soil-quality index scale.21 greatly by location in ways that are
tion of wind and rain-borne nutri- Evidence increasingly suggests a not described. The following may
ents, and microbial symbioses such fundamental contrast exists between result:

3. NOVEMBER/DECEMBER 2003 3
WINEGROWING
• Applying too much compost with
Table III: Worksheet for Whole Vineyard
an imbalance of growth resulting.
Nutrient Budget with Composting
• Using compost at the wrong time,
to no benefit. INPUT SIDE N – K – Ca – OM OUTPUT SIDE N – K – Ca – OM
• Not checking the ingredients or Based on 3 ton yield + manure Based on 3 ton/acre grape yield
quality of compost sufficiently, and Pomace + 49, 62, 59, 1000 Wine grape removal 14, 15, 15, –
finding contamination later. Manure (a)
• Overlooking subtle uses that bring Lost only in juice (b) 6, 9, 9, –
important benefits, such as the Deposition (c) 11, 0, 2,100 Erosion (d) 5, 8, 20, 300
value of light applications. N-fixation(e) 10, 0, 0, 100 Leaching & 15, 5, 0, 1200
mineralization(f)
The largest uncertainty about com-
Supplements + 10, 5, 5, 0 Prunings not 6, 7, 14, –
post is whether benefits are purely of Soil tillage (g) recycled (h)
a microbial nature. Stating that the Total Input 80, 67, 66, 1200 Total Removal 31, 29, 43, 1500
purpose of compost is to provide Est. available(i) 38, 57, 56, 1200
microbes to the soil can be misleading.
Notes to Worksheet:
Recent scientific reports show that
(a) 3 tons yield = 1.1 tons pomace + 1 ton manure (as is)
microbial populations and ratios in (b) estimate using 150 gals/juice/ton and nutrient fractioning into wet/solid portions
soil are highly stable, and are mostly (c) Estimates for wet & dry precipitation, CA-EPA
dependent on geological and physical (d) 10 ton/acre loss rate, from NRCS Soil Loss tables.
(e) assuming cover crop in 1/2 rows at 1/3 field density
traits.17 (f) OM mineralization of 2%/yr of 3%OM soil
Moreover, these reports indicate (g) tilling releases more N, based on experience
that microbe populations in soils do (h) UC-Davis estimate of 1,300-1,500lb/a canes
(i) compost availability N=15%, K & Ca = 85%
not appear to be appreciably influ-
enced by temporal practices such as
tillage and application of organic
matter. 18 These findings are consis- the following spring, resulting from range of one million to 100 million
tent with some observations from overwintering of spores on litter and per gram. Each laboratory technique
low-input vineyards that have been prunings.8 for determining soil microbial diver-
successful for generations. The dis- Unfortunately, these positive ele- sity produces its own numerical
covery that indigenous soil ments of compost all depend on the results, and interpretation schemes
microbes are very stable supports confounding relationship of disease vary tremendously.12
the notion that the native soil has pressure to meteorological events Can a healthy soil be successfully
much to offer. and vineyard management and com- inoculated with compost microbes?
Microbes in compost cannot be post quality. As a further caution, it Microbes and organic matter in
ignored, however. An example of the is generally true that the more dis- compost are food for healthy soil
hard-to-quantify benefits from com- ease pressure there is, the less microbes. In the case of an impover-
post is in the area of plant disease chance that compost will have a sat- ished soil, there could be apprecia-
suppression, a controversial topic. isfactory controlling influence. ble benefits, but we do not know
Working with grape powdery A German summary of vineyard how to determine this. Growers
mildew (Uncinula necator) in Alsation microbial compost shows the best need to be guided by experience. We
vineyards, we have shown that a results to be expected for Uncinula are very suspicious of ideal ratios or
variety of compost applications may necator, with variable results from quantities of microorganisms in a
significantly reduce the fungal inci- Plasmopara viticola, and unsatisfac- soil that can be managed. To our
dence.9 tory control of Botrytis cinerea.16 A knowledge, this has never been
When compost is broadcast recent study reported in Oregon proven.
directly onto the soil surface, it with compost extracts (tea) used for Woods End Lab has attempted to
apparently aids in the decay of the Botrytis in vineyards produced inoculate compost with selected
litter, and competes with disease- inconclusive findings.25 microbes. The result has been that
causative fungi harbored there. Predicting microbial benefits of the introduced bacterial species suc-
Laboratory studies have confirmed compost can be frustrating. For exam- cumb very quickly to pressure from
that compost microbes inhibit fungal ple, on a pound-for-pound basis, com- existing populations. Apparently,
conidia germination. Field plot stud- post does not necessarily contain these introduced microbes are
ies in vineyards have confirmed that more microorganisms than healthy unable to compete with the better-
this reduces ascospore production soil does, which is usually in the established, indigenous community.10

4. 4 NOVEMBER/DECEMBER 2003
WINEGROWING
K-Ca. The majority of the P-K-Ca will
be readily available, since there are
no factors in compost that hold onto
these elements strongly. However, it
is uncertain how much nitrogen will
be made available — the more aged
and mature the compost, generally
the less N is available.
The moisture content of the soil
where compost is applied also plays
a large secondary role in the actual
release rate. But if only one-fifth of
the nitrogen is made available, then
4 tons of compost provides 20 lbs of
available N. In contrast, a 3-ton
crop of grapes removes approxi-
mately 14 lbs/N. 15 Below are other
factors that must be known before
concluding this is the right amount
of nutrient.
The low rate of N release from
compost may be fortuitous, since it
is essentially what is desired in a
vineyard; otherwise, one could not
even apply one ton of compost
without potentially stimulating
excessive vigor. Trial and error are
required to set the application rate
to match the vigor.
We have been involved with
sites, such as the McNab Ranch
(Ukiah, CA), where vigor is such
that applying even one ton/acre of
pomace compost is unnecessary.
Other similar sites are found
throughout wine growing regions.
The primary way to reduce soil
vigor is to use grass cover crops to
absorb nitrogen and water and then
reduce or eliminate tillage and irri-
gation. Theoretically, if there is too
much N-release from a compost, it
can be managed with these tools.
Still, others have reported some suc- Balancing nutrients and These facts about compost and
cesses. composts nutrient release may seem a curious
The variable results are not surpris- It is important to not lose sight of contradiction to sustainable man-
ing; they match recent reports from the nutrients that occupy a signifi- agement and compost recycling.
European microbial research. The idea cant fraction of compost (see Figure Nevertheless, truly “natural” viti-
of importing microbes from some I). Table II shows the composition of culture will always mean using the
external source, and thereby signifi- finished grape pomace compost, soil’s best abilities to produce a
cantly improving or altering a soil or made according to the recipe from crop. Compost can be a way to care-
compost, seems naive. However, we Part I (PWV, Sept/Oct 2003). fully supplement with site-specific
won’t deny there are important dis- A single ton of pomace compost nutrients covering short and longer
coveries to be made here. provides a significant amount of N-P- term depletion from grape removal.

5. NOVEMBER/DECEMBER 2003 5
WINEGROWING
Conservative recycling of com- ton of mixed manure. The model
post — returning pomace year after assumes this amount is then re-
year via composting to the site where applied to each acre, although this
it came from — thus leads to a may not necessarily apply in every
uniquely genuine form of nutrient situation.
support for grape yields and flavor In addition to assuming a certain
which is highly site-specific. yield and recovery, several estimates
of probable losses plus other gains
Vineyard nutrient budgets are predicted. Environmental gains
With these points in mind, the and losses in a growing system are
new vineyard input formula clearly variable and sometimes very Monitoring active compost for temperature
(long-stemmed probe) and oxygen (digital
becomes: soil reserves released by high.24 Many remain largely membrane meter). If the temperature is
natural weathering + available nutri- unknown in the absence of a good very high and/or oxygen is very low
ents in entire soil-profile + microbial way to measure them. (under 2%), the pile may be turned.
augmented release of nutrients + This is where, in the end, careful
added nutrients from recycled com- visual observation of vigor and qual- by natural mineralization is also
post + other supplements, N-fixation ity are important — the model gets closely covered. Soil cover crops con-
inputs, wind deposits, rain deposited adjusted accordingly, up or down. tribute organic matter and were not
nutrients + reduced disease pressure Up if the predictions are too pes- added in this model.
= total input factors for plant devel- simistic, and down if too optimistic. Note that the total-nitrogen input
opment. Most of these can be quanti- With experience, it is easy to deter- in the model using compost appears
fied. mine if a budget model is relevant or high compared to its removal.
Table III shows a nutrient budget not. However, only a fraction of the total
with the input and outputs for the Note: Even where there are num- N from natural sources is plant-
major nutrients plus organic matter bers, a nutrient budget is never an available in any season. We assumed
compared side by side. exact science. But neither is soil test- 15% availability in the first year after
In preparing a nutrient budget, ing. Soil chemical tests give nutrient compost application.
many assumptions must be made values by a particular extraction for a A UC Davis study comparing the
and then adjusted for a particular thin topsoil layer, even though roots nitrogen benefits in vineyards from
vineyard and location. There is no may be exploiting much deeper lay- various cover crops and compost
ideal budget or single scheme. It is ers. ranked compost on the low end.13
somewhat analogous to preparing a Tissue testing is often done, and is Therefore, on light soils where N-
business plan, and then substituting thought of as sharpening estimates supply is very critical, it is important
actuals for projections as information made from a soil test. However, tis- to know more precisely the potential
becomes available. sue concentrations must be inter- N-release for a compost. There are
In Table III, actual analyses of preted by comparing them to tables lab tests to measure N-mineraliza-
pomace compost are used. The for the appropriate variety and tion from compost. Since site and cli-
model assumes a 3-ton/acre grape region, if available. In this way, all mate have so much to do with per-
yield. Clearly, the only substantial models have validity but also limita- formance, trial and error in the
nutrient removal is in the pressed tions. vineyard will be essential, however.
juice. However, not all nutrients in We are cautious about the value of
juice are actually removed, as some soil and tissue tests in established Conclusion
return in the pomace, and therefore vineyards. These are tools that are The satisfying finding here is that
go back into the input side of the very valuable for start-up years and the system represented in this model
equation. where deficiencies are observed. does not appear to be too far off.
It is assumed that all pomace after Using the whole-system budget Remove one or another factor, espe-
pressing is composted using the for- approach, some surprising conclu- cially the recycled pomace, and it
mula of a 50% addition of manure to sions result. In the example pro- changes enormously. Increase the
balance the pomace, which results in vided, the end-effect of composting production demand and eliminate
an increase of the nutrient input. pomace from a 3-ton grape yield is nutrient recycling from the pomace,
Thus, from a wet yield of 6,000 that there are enough inputs to offset and this worksheet quickly turns
lbs/acre of grapes, one ton of wet the calculated nutrient removal and into red ink!
pomace results after pressing, which estimated losses for N-K-Ca for all If one is not recycling one’s own
is combined with approximately one sources. Net loss of organic matter pomace via compost, then purchases

6. 6 NOVEMBER/DECEMBER 2003
WINEGROWING
of compost should be tied to a grape 5. Seguin, G. (1986) “Terroirs– A pedol- 16. Fischer, B. (1996). Beiträge-zur
production model, otherwise the ogy of wine growing.” Experientia, 42: 861- Entwicklung Umweltschonender Pfanzen-
inputs may be too high or too low. 872. schutzsysteme im Weinbau. “Contributions
6. Larney, F. J., L. J. Yanke, J. M. Miller, to Environmental Pest Control in Vine-
This is why we recommend assessing
T. A. McAllister (2003). “Fate of Coliform yards,” Univ. Bonn Dissertation
the production objectives before Bacteria in Composted Beef Cattle 17. Girvan, M., et al. (2003). “Soil Type
applying a model. True, it is an Feedlot Manure.” J. Environ. Qual. Is the primary Determinant of the Compo-
exploratory process, requiring some 32:1508-1515. sition of the Total and Active Bacterial
experimentation. 7. Brinton, W. (2003). “Complexity and Communities in Arable Soils.” Appl. Env.
The important caveat, to adapt an Charade in the World of Soil Microbes: A Microbiol. 69:1800-1809.
old saying, is: An ounce of visual Plea for Balance.” Journal Biodynamics Vol. 18. Sessitsch, A., et al. (2001). “Microbial
observation of the grapes may be 2. Population Structures in Soil Particle Size
8. Brinton, W., and A. Traenkner (1996). Fractions of a Long Term Fertilizer Field
worth a pound of input of compost.■
“Investigations into Liquid Compost Experiment.” Appl. Env. Microbiol. 67: 4215-
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William F. Brinton, Ph.D. studied 9. Brinton, W. (1997). “Compost for 19. Odell, R. T., W. M. Walker, L.V.
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Alan York, past president of the
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