NOVEMBER/DECEMBER 2003 PART II S U S TA I N A B L E composting BY Will Brinton & Alan York IN THE VINEYARDI 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-holdingunderstanding 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 haveof the world’s most recognized vine- tem. New World opinion has tended to from common agronomic rules foryards is very revealing in regard to soil minimize the role of soil and instead to fertilization and attainment of yieldquality. 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 havereality 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 isand 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 surfaceproduction areas, vine varieties, residues and nutrients, supplemented if compost has been layered heavily onripeness and alcoholic strength, yields, only to the extent needed (see Part I, the soil. The shock to the grapes comesviticulture (vine density, pruning, vine PWV Sept/Oct 2003) to make compost- later, under dry conditions, when thesetraining 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 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 andRothamsted, 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, singleadditions 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 theafter 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 willing no fertilizer stabilized at sustainable, attest. Comprehensive farm studies Compost, a balanced approachlow 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 treatingreserves 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 isolatedDr. G. Seguin provides an excellent graphical regions and correlated from but rather in addition to thebasis 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 tosoils 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 benefitsthe gradual and very slight natural inputs, had lower yields but scored higher expected. Or the benefits varyweathering of soil minerals, deposi- on a soil-quality index scale.21 greatly by location in ways that aretion of wind and rain-borne nutri- Evidence increasingly suggests a not described. The following mayents, and microbial symbioses such fundamental contrast exists between result:
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, 1500purpose of compost is to provide Est. available(i) 38, 57, 56, 1200microbes 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 portionssoil are highly stable, and are mostly (c) Estimates for wet & dry precipitation, CA-EPAdependent 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 densitytraits.17 (f) OM mineralization of 2%/yr of 3%OM soil Moreover, these reports indicate (g) tilling releases more N, based on experiencethat 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 astillage and application of organicmatter. 18 These findings are consis- the following spring, resulting from range of one million to 100 milliontent with some observations from overwintering of spores on litter and per gram. Each laboratory techniquelow-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 numericalcovery that indigenous soil ments of compost all depend on the results, and interpretation schemesmicrobes are very stable supports confounding relationship of disease vary tremendously.12the notion that the native soil has pressure to meteorological events Can a healthy soil be successfullymuch 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 inignored, however. An example of the is generally true that the more dis- compost are food for healthy soilhard-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 knowWorking with grape powdery A German summary of vineyard how to determine this. Growersmildew (Uncinula necator) in Alsation microbial compost shows the best need to be guided by experience. Wevineyards, we have shown that a results to be expected for Uncinula are very suspicious of ideal ratios orvariety of compost applications may necator, with variable results from quantities of microorganisms in asignificantly reduce the fungal inci- Plasmopara viticola, and unsatisfac- soil that can be managed. To ourdence.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 toapparently aids in the decay of the Botrytis in vineyards produced inoculate compost with selectedlitter, and competes with disease- inconclusive findings.25 microbes. The result has been thatcausative 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 fromthat 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 areies 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 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 andcesses. 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 theexternal source, and thereby signifi- finished grape pomace compost, soil’s best abilities to produce acantly 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-specificwon’t deny there are important dis- A single ton of pomace compost nutrients covering short and longercoveries to be made here. provides a significant amount of N-P- term depletion from grape removal.
NOVEMBER/DECEMBER 2003 5 WINEGROWING Conservative recycling of com- ton of mixed manure. The modelpost — returning pomace year after assumes this amount is then re-year via composting to the site where applied to each acre, although thisit came from — thus leads to a may not necessarily apply in everyuniquely genuine form of nutrient situation.support for grape yields and flavor In addition to assuming a certainwhich is highly site-specific. yield and recovery, several estimates of probable losses plus other gainsVineyard nutrient budgets are predicted. Environmental gains With these points in mind, the and losses in a growing system arenew vineyard input formula clearly variable and sometimes very Monitoring active compost for temperature (long-stemmed probe) and oxygen (digitalbecomes: soil reserves released by high.24 Many remain largely membrane meter). If the temperature isnatural weathering + available nutri- unknown in the absence of a good very high and/or oxygen is very lowents 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, carefuladded nutrients from recycled com- visual observation of vigor and qual- by natural mineralization is alsopost + 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 notnutrients + 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 inputopment. Most of these can be quanti- With experience, it is easy to deter- in the model using compost appearsfied. 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 totalwith 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 assumedcompared 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 theand then adjusted for a particular thin topsoil layer, even though roots nitrogen benefits in vineyards fromvineyard and location. There is no may be exploiting much deeper lay- various cover crops and compostideal budget or single scheme. It is ers. ranked compost on the low end.13somewhat 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 importantactuals for projections as information made from a soil test. However, tis- to know more precisely the potentialbecomes 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 thenutrient removal is in the pressed tions. vineyard will be essential, however.juice. However, not all nutrients in We are cautious about the value ofjuice are actually removed, as some soil and tissue tests in established Conclusionreturn in the pomace, and therefore vineyards. These are tools that are The satisfying finding here is thatgo back into the input side of the very valuable for start-up years and the system represented in this modelequation. 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 itmula of a 50% addition of manure to sions result. In the example pro- changes enormously. Increase thebalance the pomace, which results in vided, the end-effect of composting production demand and eliminatean 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 turnslbs/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 ownis combined with approximately one sources. Net loss of organic matter pomace via compost, then purchases
6 NOVEMBER/DECEMBER 2003 WINEGROWINGof compost should be tied to a grape 5. Seguin, G. (1986) “Terroirs– A pedol- 16. Fischer, B. (1996). Beiträge-zurproduction 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 Dissertationthe production objectives before Bacteria in Composted Beef Cattle 17. Girvan, M., et al. (2003). “Soil Typeapplying 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 Bacterialexperimentation. 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). “Microbialobservation 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 Fieldworth a pound of input of compost.■ “Investigations into Liquid Compost Experiment.” Appl. Env. Microbiol. 67: 4215- Extracts.” Biocycle. 37:68-71. 4224. William F. Brinton, Ph.D. studied 9. Brinton, W. (1997). “Compost for 19. Odell, R. T., W. M. Walker, L.V.agronomy and environmental science Control of Grape Powdery Mildew.” Jrnl Boone, and M. G. Oldham (1983). “Theand is founder and director of Woods Biodynamics Vol 3. Morrow Plots: A Century of Learning.”End Research Laboratory, Mt. Vernon, 10. Droffner, M. and W. Brinton (1994). Illinois Agric. Exp. Stn. Bull. 775.Maine with a branch office in Europe. “Microbial Approaches to the Character- 20. Smart, R. E. and J. Gladstones ization of Composting Process.” Compost (1999). “Soil and Wine Quality.” In The Alan York, past president of the Sci. Util. Vol. 2. Oxford Companion to Wine. 2nd Edition. J.Biodynamic Agricultural Association, is 11. Droffner, M. and W. Brinton (1995). Robinson (Ed) Oxford Univ. Press.a trained horticulturist and is an inter- “Evidence for the Prominence of Well 21. Reganold, J. P., A. S. Palmer, J. C.national consultant for wine grape Characterized Mesophilic Bacteria in Lockhart, and A. N. Macgregor (1993).growers. Thermophilic Composting Environments.” “Soil Quality and Financial Performance of Biomass & Bioenergy 8:191-195 Elsevier Sci Biodynamic and Conventional farms in References Ltd. New Zealand.” Science. 260: 344-349. 1. Doran, J. W., D. F. Bezdicek, D. C. 12. Dunbar, J. et al., (2002). “Empirical 22. Reganold, J. P., J. D. Glover, P. K.Coleman, and B.A. Stewart (1994). “Defining and Theoretical Bacterial Diversity in Four Andrews, and H. R. Hinman (2001).Soil Quality for a Sustainable Environment.” Arizona Soils.” Appl. Env. Microbiol. 68: “Sustainability of Three Apple ProductionSoil Sci. Soc. Amer. Spec. Publ.# 35 , Madison, 3035-3045. Systems.” Nature. 410: 926-930.WI. 13. Hirschfelt, D., W. Peacock, P. 23. Blanchard, C. H., M. and S. 2. Leigh, R. A., A. E. Johnson (1994). Long- Christensen (1992). “The Effects of Cover Tanenbaum, (1996). Regional Estimatesterm Experiments in Agricultural and Ecological Crops and Compost on Grapevine of Acid Deposition Fluxes in California.Sciences. CAB International, London. Nutrition and Growth.” Univ. California- Air Resources Board, CA-EPA. No. 96- 3. Schiller, H., J. Gusenleiter, E. Lengauer, B. Davis SAREP. 13.Hofer (1967). Fruchbarkeitstörungen bei Rindern 14. Homeyer, H. (2003). “A Magical 24. Soule, J. J., J. Piper (1992). Farming inin Zusammenhang mit Düngung, Flora und Organic Elixir Goes High-Tech.” New York Nature’s Image; An Ecological Approach toMineralstoffgehalt des Wiesenfutters. Linz Times. Jan. 5, 2003. Agriculture. Island Press.Agricultural Experiment Station, Linz Austria. 15. LIVE (2000). “Soil and Fertilizers.” 25. SARE (2003). “Control of Botrytis by 4. Robinson, J. Ed. (1999). The Oxford In Low Input Viticulture and Enology. Oregon Compost Tea Applications on Grapes inCompanion to Wine 2nd Edition. Oxford Univ. State Univ. http://berrygrape.oregon Oregon.” Western Region SARE ProjectPress. state.edu/LIVE/. SW00-039. http://wsare/usu.edu. Reprinted from: 58 Paul Drive, Ste. D, San Rafael, CA 94903 • 415-479-5819 Visit our website: www.practicalwinery.com to learn more about PWV.