BY Glenn McGourty, Viticulture and Plant Science Advisor University of California CooperativeExtensionMendocino and Lake Counties

Vineyard cover cropping practiceshave been refined in Mendocinoand Lake counties over the past 15years. When organic and sustain-

able winegrowing began in the late1980s, many of the cover crop specieswere selected from agronomic cropfarming systems. While these were well-suited for bringing “life” back into thesoil, they weren’t ideal species for a vine-yard. Many were simply too energy-intensive to farm; too vigorous, grewinto the trellis, produced too much bio-mass to manage easily, or produced toomuch nitrogen in the soil.

Following multiple trials conductedby the author and cooperating grow-ers, we have identified a broad “plantpalette” from which to choose in

addressing specific cultural issues invineyards, such as protection from soilerosion while building soil structure,organic matter, and overall soil quality.

Cover crops are now recommendedthat better fit the architecture of a vine-yard and the farming system that grow-ers find appropriate for their vineyards.

In Mendocino and Lake counties,both conventional, sustainable, and cer-tified organic farming systems usecover crops. The differences betweencover crop farming practices in thesesystems are slight.

Organic winegrowers do not useany herbicides or syntheticallyprocessed concentrated fertilizers.They rely on compost for nutrients.(Compost also makes a significantcontribution to the goal of buildingsoil carbon, as it contains fairly stablehumus-like compounds.)

Under-vine weed control is donemostly with tillage tools. Both wine-growing systems use many of the samecover crop species, managed in similarways.

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Cover croppingsystems for organicallyfarmed vineyards

Alternate middles planted to brown mustardand Daikon radish (planted annually) andsubterranean clovers (farmed non-till forthree seasons.)

Non-till cover crop sward of subterranean clover in late spring.

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This report will examine how organicwine growers select cover cropping sys-tems, and what techniques are used togrow and manage them in North Coastvineyards.

Importance of cover cropsCover crops are a tool to help wine-

growers manage their soils in multipleways. They help to:• PROTECT SOIL FROM EROSION: The foliageof cover crops reduces the velocity of rain-drops before they hit the soil surface, pre-venting soil from splashing. This preventsslaking of soil aggregates and sealing ofthe soil surface. (When this occurs, runoffincreases, along with soil erosion). Theroots of the cover crops bind soil particlestogether, improving soil structure andwater penetration, while preventing thesoil particles from moving.• REGULATE VINE GROWTH: Cover crops canbe used to both invigorate vines (aug-menting soil nitrogen from nitrogen-fix-ing legumes) and devigorate vines (rootcompetition from non-legumes with thevines for nutrients and water).• IMPROVE SOIL FERTILITY: Besides increasingsoil nitrogen, decomposed cover cropsincrease the soil cation exchange capacity.Therefore, the ability of a soil to hold andexchange nutrients increases.Additionally, nutrients are often chelatedinto organic complexes, and are morereadily exchanged from these substratesthan from inorganic clay minerals. Sincemany organic growers also apply com-post, this also adds to the fertility of vine-yard soils.• IMPROVE SOIL STRUCTURE AND WATER HOLD-ING CAPACITY: Initially, cover crop roots helpaggregate soils as fine roots penetrate thesoil profile (especially grasses). Covercrops with large tap roots help to createmacropores when the plants die, and avoid is left from the decomposing roots.These macropores greatly assist themovement of air and water into the soilprofile.

Soil organisms using the decomposingcover crops as a food source create waxesand other sticky substances that hold thefine particles into aggregates, loweringbulk density and improving soil tilth. Asorganic matter increases in the soil, sodoes the soil’s ability to hold water.

Physical improvement of the soil isimportant, because, large root systemsare very desirable in organic wine-growing. Since soil nutrient concentra-tions may be lower than convention-ally farmed vineyards, and since manyorganic winegrowers prefer not to irri-gate, a root system that foragesthrough a larger area of the soil profileis more likely to provide what a vineneeds.

Many organic winegrowers feel thatrelying more on the soil than on a bagof soluble fertilizer applied throughthe drip system to provide water andnutrients will be a better expression ofa vineyard site’s terroir.• ENHANCE BIOLOGICAL DIVERSITY IN THEROOT ZONE: Organic matter is a foodsource for macro- and micro-organ-isms. Many of these organisms assist inrecycling cover crops into the soil,while improving soil physical qualitiesin the process. Particularly noteworthyare increases in earthworm popula-tions; they are a good indicator of soilhealth and improved physical condi-tions.

Increased biological activity occursin the soil after the incorporation oforganic matter from cover crops.Researchers have clearly shown thatthese organisms can reduce damagefrom root pathogens by inhibiting theirgrowth and development.• PROVIDE HABITAT FOR BENEFICIAL GENERAL-IST PREDATOR AND PARASITOID INSECTS ANDARACHNIDS (SPIDERS AND MITES): Since pestmanagement strategies in organicwinegrowing emphasize reliance onnature and the use of “soft” chemicals,it is important that beneficial arthro-pods are abundant and in close prox-imity to the vineyard to control harm-ful insects and mites.

Cover crops can provide habitat andfood for beneficial insects at differentstages of their life cycle. They also pro-vide habitat for prey, such as aphids,mites, caterpillars, and other creatures.Research entomologists have a difficulttime understanding the dynamics ofpest and prey relationships in thecover crop, and their effects ongrapevine canopies. Regardless, grow-ers report experiences of reduced

leafhopper and mite problems whencover crops are planted in lieu of con-ventional insecticide applications.• PROVIDE FIRM FOOTING FOR HARVEST ANDCULTURAL OPERATIONS: When no-till, sod-forming cover crops are planted, theresulting firmer footing makes vine-yard operations during wet weathermore feasible. This can enable harvest,pruning, and spraying during incle-ment weather.• IMPROVE AIR AND WATER QUALITY: Waterquality laws are being increasinglyenforced, and vineyard water runoffneeds to be free of silt and excess nutri-ents. Cover crops help to preventerosion. Nitrogen formed by legumesis less mobile than soluble nitrogen fer-tilizers. Cover crops assimilate freenutrients in the soil, and stabilize themduring periods of high rainfall. Duringthe dry periods of the year, cover cropshelp reduce dust, improving air qual-ity. This also helps to reduce the prob-lem of mite infestations, which inten-sify under dusty conditions.

Cover cropping farming systemsChoosing a cover cropping farming

system will depend on the relativevigor of the site; water availability inthe soil; viticultural objectives (increas-ing or decreasing vegetative growth);and pest management objectives forinsect, mite, and weed control.Following are discussions of severaldifferent approaches.

Annually tilled and seeded: Themajority of growers using this systemchoose it to conserve moisture in theirvineyards. Cover crops are planted inthe fall, allowed to grow until somepoint in the spring when the groundcan be easily cultivated, and thenmowed and tilled into the soil. Thisoperation is often timed when thecover crop is flowering, as it willdecompose easily at this stage. Thissystem is best suited for relatively flatvineyards in which soil erosion is not aserious hazard.

Cover crop species typically used inthis system include annual smallgrains (barley, oats, triticale), winterpeas, common vetch, bell beans,daikon radish, Persian clover, and

other annuals that grow well during thecool months.

In upland areas prone to soil erosion,where water is not available for irriga-tion of either the vines or the cover crop,it is highly recommended to use strawmulching or compost “overs” (coarseparticles between one and two inches insize) to minimize the loss of soil fromthe vineyard while waiting for the covercrop to start growing in the fall.

This farming system is tillage-inten-sive, and soil is exposed to sunlightduring the summer. Loss of soil struc-ture and organic matter occurs if tillageis excessive. Regardless, many growersusing this system believe it allows themto grow very high quality fruit withoutirrigation or concentrated fertilizerapplications.

Many people like the looks of culti-vated vineyards, and this often is the

method of choice near expensive andattractive winery facilities (particularlyin Napa Valley).

Non-tillage vineyard floor manage-ment with annual cover crop species

In a no-till system with annual covercrops, the vineyards are tilled initiallyand seeded with species that will reseedthemselves on an annual basis.Thereafter, the vineyards are mowed in

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ANNUAL LEGUMES

‘Magnus’ Winter Peas (Pisumsativum): This low growing, floppycover crop germinates well in cool,moist weather, and produces moder-ate amounts of biomass and nitrogen.It has attractive pink and white flow-ers, and has light winter dormancy, soit grows well in the early spring. Whileit will twine its way up when mixedwith other cover crops such as smallgrains, it isn’t aggressive, and won’tend up in the vineyard trellis. Used inannually tilled systems. Seeds aremedium in price (about $50 per acre).

Subterranean Clover (Trifolium sub-terraneum): the queen of leguminouscover crops for no till vineyard covercropping systems! Does well in acidsoils. Low growing and self reseeding,this cover crop produces moderateamounts of nitrogen and biomass.Grows mostly when grapevines aredormant, so it is not a big competitorfor soil moisture. Cultivars ‘Anthis,’‘Koala,’ and ‘Mt. Barker’ are morewinter-dormant and produce the mostbiomass. Seeds are medium in price(about $50 per acre).

Bur Medic (Medicago polymorpha):germinates and grows well in areaswith limited rainfall, but doesn’t likeacid soils. Excellent reseeding capabil-ity for no-till vineyards. Respondsvery well to liming. Low growingmoderate producer of biomass andnitrogen. Don’t like burs in yoursocks? Try bur-less selection ‘Santiago’bur clover. Seeds are medium in price(about $50 per acre).

‘Flame’ crimson clover (Trifoliumincarnatum): one of the prettiestlegumes, grows to low height (about14 inches) and is covered with profusered blooms in late spring. Producescopious biomass that can be hard toincorporate sometimes. Very competi-tive with weeds. For tilled vineyards.Seeds are medium in price (about $50per acre).

ANNUAL FORBSDaikon radish (Raphanus sp.): This

tall growing radish forms large tap-roots that help to open up clay soils.Blooms profusely, and provides habi-tat for beneficial insects and their prey.Germinates well under cool and moistconditions. Attractive and interestingcover. Cheap to plant (around $30 peracre).

ANNUAL GRASSES AND SMALL GRAINS‘Zorro’ fescue (Vulpia myuros var.

hirsuta): A low growing and earlymaturing grass suited for non-tillagevineyards. Germinates early, andgrows well under low rainfall. Prolificseed producer. Can be mixed withannual self reseeding legumes. Seedsare expensive (about $80 per acre).

‘Blando’ brome (Bromus hordeaceusssp. molliformis): Produces more bio-mass than ‘Zorro’ fescue, but still islow-growing and matures early. Goodchoice for non-tillage vineyard floormanagement. Germinates well underlow rainfall conditions. Can be mixedwith self-reseeding annual legumes.Seeds are medium in price (around$50 per acre).

‘Juan’ triticale (x Tritosecale): Thisplant is ideal for stabilizing soil duringvineyard installation. It forms a big,fibrous root system, germinates wellunder cool and moist conditions, andhas a long winter dormancy, so itdoesn’t bolt early, allowing time to tillit into the soil while it is relativelysmall in stature and biomass. If left tomature, it can produce five tons to theacre of straw, so it is very productive.Useful for mixes with annual legumesfor annual tillage cover cropping sys-tems. Seed is inexpensive (about $30per acre).

PERENNIAL GRASSES

Fine fescues, including hard fescue,sheep fescue, and red fescue (Festucaovina, Festuca ovina var. duriuscula,Festuca rubra): These grasses are goodchoices for vineyards with moderatevigor that are managed by mowingonly. They can all be mixed, althoughhard fescue and sheep fescue are thelowest growing. They will go verydormant in the summer, but green upagain with winter rains. Expensive toplant, around $120 per acre.

Turf-type perennial rye grass(Lolium perenne): The cultivars ‘Elka’and ‘Manhattan II’ form tough, weed-free turf and will also devigoratevines. Perfect for non-till, mow onlyvineyard floor management in vine-yards with good soils. May need to befertilized, or plant with perennialclovers for nitrogen. Expensive toplant, around $100 per acre.

Glenn McGourty’s top ten cover crop picks for organic vineyard cover crops in the North Coast

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spring and early summer. Tillage isrestricted to only beneath the vines.Subterranean clovers, rose clovers, crim-son clover, red clover, berseem clover,bur medic, bolansa clover, and Persianclover are all suited for this farming sys-tem. Grasses that can be used includeBlando brome and Zorro fescue.

Another no-till approach is plantingannual cover crops that are not self-reseeding, such as oats, barley, peas andvetch, with a no-till drill. This approachis useful when tillage could cause ero-sion, and it is desirable to keep tillage toa minimum. Usually, seeding is donejust before fall rains. The cover crop issimply mowed and left to lie on the soilsurface.

Non-tillage vineyard floor manage-ment with perennial species

Perennial species are most commonlyused in vineyards planted on fertilesites. Many of the perennial grasses arevery competitive with grape vine roots,and will have a devigorating effect onthe vineyard. This may be desirable ifthe vineyard is seriously out of vegeta-tive balance.

There is a range of cover crops thatvary from being slight to very competi-tive. The fine fescues (hard fescue,creeping red fescue, and sheep fescue)are the least competitive, grow veryshort, and survive well.

Turf selections of perennial rye grassand tall fescue are intermediate in theircompetitiveness. They have fairly lowstature, and require mowing only onceor twice per year.

Pasture selections of perennial ryegrass, tall fescue, and orchard grassare the most competitive, and canhave a tremendous impact on vine-yard vigor. They should be planted ononly the most vigorous sites withdeep soils.

These grasses may also be used inparts of the vineyard that are proneto erosion, or places where it is desir-able to reduce dust. Seasonal water-ways, vineyard roads that aren’theavily trafficked, turn-around areas,staging areas, or other places wherethe soil needs to be protected arepotential sites for these grasses.

There is a good case for includingperennial legumes in a sward ofgrasses, as they will supply nitrogenfor the grasses. Unfortunately, theymay also attract rodents such as volesand gophers, which can damagegrapevines. Despite this potentialproblem, many growers also includewhite clover, strawberry clover,alsike clover, and birdsfoot trefoil ina perennial mix. These species pro-vide not only nitrogen for thegrasses, but also habitat for general-ist predator and parasitoid insects.

Some growers have had successplanting perennial grasses alone, andthen,after two or three seasons,planting annual legumes into thesward. If the annual legumes andperennial grasses are initially plantedtogether, the legumes will shade thegrasses out, and a poor stand ofperennial grasses is likely to occur inthe sward.

California native grasses can alsobe used as cover crops. Favoritesinclude pine blue grass, mokulemne,and molate red fescue as less compet-itive species; and California brome,meadow barley, and blue wild rye asmore competitive choices. Seed isexpensive for these grasses, and theyare not as competitive with weeds insome cases as other pasture grassspecies used as cover crops.

It is important to let these grassesflower late in the spring, in order forthem to accumulate carbohydrates intheir root systems, which improvestheir persistence and competitivenesswith weeds.

Tilled and no-till farming systemsSome growers use different farming

systems in alternate tractor rows to mod-erate vigor, incorporate compost, pro-

Winter annual cover crop mix of winter peas, bell beans, and oats.

Summer cover crop of sunflowers plantedfor beneficial insect habitat, diversity andbeauty. Bonterra Vineyards.

vide diverse habitat, or for aesthetic rea-sons. One system commonly employeduses a no-till approach of self-reseedingannuals for three years in alternate tractorrows, with annually planted and ploweddown cover crops in other tractor rows.

After three years, the planting systemsare switched to alternate tractor rows.Perennial species are also used in thisway. In most cases, this approach is usedon more vigorous sites not prone to soilerosion.

Cover crop rotationOver time, cover crops can develop

pests and pathogens that make it difficultto reseed the same species year after year.That is one reason why mixes are planted,as the effect of planting the same speciesannually seems less pronounced when amixture of diverse species are used.

Sometimes, growers will use com-pletely different species from year to year,such as mustards or radishes, followed bylegumes, which are then followed byannual grains. Other growers take theapproach of mixing all three togethersimultaneously, believing that there is anadjustment in species composition in thesward to the particular season’s growingconditions.

Cultural practices for cover crops SEED SOURCE

Cover crop seed should be purchasedfrom dealers who sell quality seed thathas been tested for viability and is free

from weed species. Under organic certifi-cation laws, growers are obliged toattempt to source organically grown seed.Unfortunately, this is nearly impossiblefor many of the small seeded cover crops,which are not even grown in the U.S. Youare required to document in writing foryour certification records that youattempted to purchase organic seed, eventhough conventionally grown cover cropseed can be used in organically-certifiedvineyards.

SEEDING

Being agronomic crops, most covercrop species grow best when planted ina well-prepared seed bed with ade-quate fertility. Usually, this requirestwo diskings, harrowing, and firmingthe soil with a ring roller or cultipackerprior to seeding. If the ground is some-what compacted, it may be necessary toshallowly rip the area to be planted to adepth of about 12 inches with a tool barand shanks, especially where wheeltraffic occurs in tractor rows.

Seeding can be done with severaldifferent implements. For small areas,hand broadcast spreaders (“bellygrinders”) can be used. Tractor-mounted broadcast spreaders are alsoused for larger areas, but are not veryprecise. Seed drills are the best choicewhen expensive seed is being plantedand accurate placement is required.

Most seed drills use two soil-cuttingblades called coulters, which are set at

acute angles to each other. These cut aslit in the soil, with seed metered froma box above them, falling through tubesthat open between the coulters. Smallwheels are located behind the coultersto pack the soil firmly after the seed isdeposited. Another alternative is a ringroller attached to the seed drill thatfirms the soil after seeding.

Slit seeders can also be used for no-till seeding. These utilize a device simi-lar to a rototiller, except that the cuttingblades are flat, and not bent at rightangles like the bolo tines typically usedon a rototiller. The seed box is mountedabove the tiller, and seed is directedinto the slits, packed by a ring rollermounted on the seeder. This seederworks best with cover crop species thathave considerable seedling vigor.

SEEDING AND IRRIGATION SEASONS

Cover crops are usually planted inthe fall, and rely on fall rains to begingermination. In cooler, shorter growingseason areas, many vineyards areequipped with overhead sprinkler sys-tems for frost protection. It is very help-ful to seed early, and then irrigate thevineyard with an inch of water fromlate September to mid-October to startthe germination process. Small seededcover crops and perennial species defi-nitely benefit from early seeding andirrigation to start germination. If rainsdon’t come immediately, additionalwater may be required.

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California poppies and annual lupine useful for “beauty” cover crop mixes.

Crimson clover, an attractive annual clover.

Perennial species can also be seededin the spring, at the same time thatwarm season summer cover crops areseeded. Late April and early May arewhen these covers can be planted. Inmany respects, it isn’t the best time toseed perennials, as they need moist soilconditions to develop an extensive rootsystem, which is more likely to occurwith fall seeding. For perennial species,

mowing will be needed to reduce com-petition from annual summer weeds.Irrigation will benefit both types ofcover crops.

FERTILIZER

Cover crops need specific nutrientsto grow well. Many organic growersuse compost, which in most cases willadequately provide what the cover

crops need. Compost made from a mix-ture of animal manure and grape pom-ace (50:50 mix) normally has enoughNPK to get the cover crops off to a goodstart. Rates vary, but most growers willstart with one or two tons per acreapplied annually. In subsequent sea-sons, less material will be used.

In the North Coast, legumes respondwell to applications of rock phosphorus

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Balansa Clover (Trifolium miche-lianum Savi) is native to southernEurope and the Mediterannean region.It is a winter annual clover that growswell in Mediterranean climates withcool, moist winters. It was introducedinto Australia in the 1950s, and hasnaturalized in many pastures through-out southern Australia.

Balansa clover can grow up to threefeet tall, but when mowed or grazed, itforms a low growing and densecanopy. It is an attractive plant, as theleaves often have purple and pinkmarkings. Flowers are white and pink,and it blooms abundantly in mid-April to early May.

It grows moderate amounts of bio-mass, similar to a vigorous cultivar ofbur clover or subterranean clover. Itproduces abundant seed, and regener-ates well in dry land conditions.

All cultivars produce high levels ofhard seed, which can germinate forseveral seasons (some agronomists areconcerned that it might be a bitweedy). Compared to subterraneanclover, it appears to germinate later incool soil temperatures. It normally isseeded at the rate of 10 lbs per acre.

Balansa clover tolerates water log-ging for extended periods of time,once germinated. It has grownextremely well in two cover crop trialsin Lake County, which is high eleva-tion (more than 1,400 feet) and verycool in the winter.

There are three cultivars of Balansaclover in the trade. ‘Frontier’ is the ear-liest flowering selection, and willflower and set seed the best in shortgrowing areas, such as places withshallow, dry soils. ‘Paradana’ is a mid-

season cultivar, and matures twoweeks after Frontier. ‘Bolta’ is 10 dayslater than Paradana, and is well-adapted to cooler and wetter sites thanothers.

Persian clover (Trifolium resupina-tum) is an annual clover for Medi-terranean climates native to Turkey,Afghanistan, Portugal, Greece, Iran,and Iraq. It was introduced intoAustralia in the 1950s, and has beengrown commercially since the 1970s.

There are two groups of Persianclovers: hard-seeded types (Trifoliumresupinatum var. resupinatum) whichare self-seeding clovers for use in pas-tures and cover crops; and soft-seededtypes (Trifolium resupinatum var. majus)used more for annual cover crop mixesthat are plowed into the soil or short-term rotations that require annualreseeding.

This excellent cover crop has excel-lent seedling vigor, grows and bloomsover a long period of time, and toler-ates water-logged soils once it has ger-minated. It is an attractive plant, withlavender to pink colored flowers, anddeep green foliage.

In California, two cultivars areavailable for planting. ‘Nitro’ belongsto the hard-seeded Persian clovergroup, and is suited for self-reseedingannual cover crop swards. It growstaller than subterranean clover, andlater into the growing season.‘Lightning’ is a soft-seeded Persianclover, and must be seeded annually. Itis taller in stature than Nitro and iswell-suited as a nitrogen builder forvineyard soils. It can be planted withsmall grains such as triticale, and is

competitive in mixed annual covercrop swards.

Persian clover seeds are quite small,and should be seeded at the rate of 10lbs per acre. It is aromatic, and attractsmany beneficial insects.

Fenugreek (Trigonella foenum-grae-cum) is a winter-growing annual nativeto southern Europe and Asia. It hasbeen used for centuries as a condiment,medicinal plant, forage, food, spice,and dye. Fenugreek is very aromatic,and has been used to make artificialmaple syrup flavor for baked goods,chutneys, and confections. Seeds areground and used in curries.

Young seedlings and other portionsof fresh plant material are eaten asvegetables. The plant is high insapogenins from which steroid drugsare refined. Pharmaceutical usesinclude antibiotic properties, soothingsore throats, expectorant, laxative, andaphrodisiac.

The fenugreek plant is erect, grow-ing to nearly three feet. It has trifoliatefoliage, white flowers, and abundantyellow-brown seed pods that producebrown seeds. It grows considerablebiomass and fixes nitrogen. It can beused as an annual cover crop in muchthe same way as winter peas, crimsonclover, or other nitrogen-fixing covercrops.

The seeds are much larger thanclovers, and should be seeded at therate of 40 to 60 lbs per acre in welltilled and prepared seed beds. In ourtrials, fenugreek is sensitive to cold,and doesn’t germinate well unlessplanted while the soil is warm, andirrigated.

Three interesting new cover crops for vineyards

one season, physically incorporatedinto the soil, followed by liming thenext season. Applications should bemade based on soil tests to ensure thatthe proper quantity of materials areapplied. Popcorn sulfur is needed insome high rainfall areas, specifically forthe legumes.

SPRING TIME MOWING

Most cover crop species benefitfrom spring time mowing, as it caneliminate shading from faster growingweed species, and promote tillering,or expansion of the plants’ crowns.For low-stature cover crops, thisshould be done just before they transi-tion from the winter dormant/basalrosette stage into mature growth andflowering. On the North Coast, thisusually occurs in early March, aboutthe same time that prunings are beingshredded. It is usually done in thesame equipment pass.

Large stature annual cover cropsare often clipped at bud break (remov-ing anything growing above 18inches) to reduce frost hazard foremerging vine growth. Tall cover cropswards are not desirable at this time,as they can impede air movement andincrease the tendency of young shootsto freeze or develop Botrytis shoot tiprot.

SPRING TILLAGE

If the vineyard is going to bedisked, the maximum addition ofnitrogen from legumes occurs whenthe legumes are incorporated into thesoil as they are blooming. Many grow-ers will first shred the cover crop witha mower, and then disk it in. This willalso improve decomposition rates, assmaller crop residues decomposefaster than large ones. Timing is veryimportant, as the soil must still bemoist enough to easily till-in the crop.Maximum nitrogen release occursabout three weeks after incorporation,assuming that the soil remains moist.

Additional tillage may be required tofully incorporate all residues, usually intillage operations spaced about 10 daysapart. A final pass is often made with aring roller to pack the soil firmly so thatit is easy to walk on, and looks attrac-tive.

LATE SPRING AND SUMMER MOWING

Self-reseeding annual cover cropsare mowed in late spring and earlysummer after seed-set in order to mini-mize dry residual growth that might beflammable, and also to mow downsummer weeds. For perennial covercrops, several mowings might berequired to keep the foliage from grow-ing excessively tall.

If California native grasses are used,there are some advantages to letting theplants flower in June and then mowingthem. Even though there can be largeamounts of foliage present, this approachallows the grasses to accumulate morecarbohydrates in their root systems, sothey survive summer dormancy betterthan if they are continuously mowed.

ConclusionCover cropping is an important compo-

nent in organic winegrowing systems.Growers enjoy numerous choices in speciesand farming systems. Organic winegrow-ing does not limit any cover crop choices,since the same crops are available as in con-ventional winegrowing systems.

Choosing a cover cropping systemshould be very site-specific. Growers mustconsider their style of farming, yield andquality objectives, and any other criteriathat they consider important. ■

More reading

Ingels, C., R. Bugg, G. McGourty, P.Christensen, 1998. Cover Cropping In Vineyards— A Growers’ Handbook UC ANR Publications#3338, Oakland, California. 162 pages.

McGourty, G. 1994 “Cover crops for NorthCoast vineyards.” Practical Winery & Vineyard15 (2): 8–15.

Miller, P.R., W.L. Graves, W.A. Williams,B.A. Madson, 1989. Cover Crops for CaliforniaAgriculture. UC ANR Publications #21471.

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