Managing floor vegetation is a prime consideration for vineyard managers. The benefits of removing resident (weedy) vegetation are well known: weeds can compete with the vines for water, nutrients, and even light, and the traditional method of protecting vine growth and yield is to keep the vineyard free of floor vegetation either through use of herbicides or cultivation. However, a vineyard floor with no vegetative cover has its drawbacks, which includes increased dust (impeding photosynthesis and increasing vine susceptibility to spider mites) and increased rate of organic matter decomposition leading to a decline in soil structure and poorer water penetration (Gulick et al., 1994). On slopes with no floor vegetation, there is an increased risk of erosion.
It has become common in California for practitioners to maintain vineyard floor vegetation for at least part of the year either by managing the resident vegetation or a planted cover crop (Elmore et al., 1998). The typical method of cover cropping is to plant an annual grass, legume, or blend in the fall, allow it to grow in winter and early spring, and cultivate it by midspring so as to minimize competition with the vines. The disadvantage to this is that during the grape-growing season, the soil remains uncovered and can be colonized by weeds. Permanent cover crops under nontillage are rare in California; although they provide continuous soil cover, there are concerns about excessive competition. Perennial legume cover crops that have been suggested for vineyard use (Ingels et al., 1998) such as white clover (Trifolium repens L.) and strawberry clover (Trifolium fragiferum L.) require summer water, making their management all but impractical except in areas with abundant irrigation water or a high soil water table. Non-native grasses maintained during the growing season compete with the grapevines for water and nitrogen and have led to reductions in grapevine vigor and yield. A cover crop of ‘Berber’ orchardgrass (Dactylis glomerata L.) increased water stress and lowered vigor and yield of ‘Cabernet Sauvignon’ by ≈50% (Wolpert et al., 1993). Costello and Daane (2003) found summer floor vegetation dominated by barnyard grass (Echinochloa spp.) and large crabgrass [Digitaria sanguinalis (L.) Scopoli] decreased leaf nitrate–nitrogen concentration and vigor of ‘Thompson Seedless’. Self-reseeding annuals can provide cover cropping benefits while minimizing in-season competition (Bugg et al., 1996). These can be grasses or legumes, which, under nontillage, set seed and senescence in the spring, leaving a dead mulch, which can outcompete weeds. The seed then germinates with the fall rains and a new stand is established. ‘Blando’ brome, a self-reseeding cover crop commonly used in California vineyards, has been found to use only a moderate amount of water (Gulick et al., 1994; Prichard et al., 1989). However, self-reseeding annuals need to be replanted every few years to revitalize the stand.
A potential alternative cover cropping system for orchards or vineyards in California, and perhaps other regions with a Mediterranean climate, is the use of native perennial grasses. These grasses should be well suited as cover crops in that their phenology is opposite that of the grapevine, i.e., their dormant period is during the summer dry season when the vines are active. Therefore, they should provide the advantages of a perennial cover crop without the disadvantage of excessive competition with the vines for water and nutrients, although this would depend on the degree of native grass summer dormancy. Since the early 1990s, there has been increased interest in the use of native grasses among commercial orchardists and viticulturists in California (Ingels, 1998).
The object of this study was to test the competitive effect on the grapevines of two California native grasses, nodding needlegrass and California barley. Each is a perennial bunch grass, which blooms in midspring and sets seed in late spring. California barley has a maximum height of 0.5 m and nodding needlegrass 0.8 m (USDA-NRCS, 2008). These were compared with ‘Blando brome’, a self-reseeding annual native to Europe; resident vegetation, which consisted of naturalized grasses and forbs from Europe and Asia; and a clean cultivated control. From the same study, data were collected on soil water content and leaf water potential from the nodding needlegrass and clean cultivated treatments and are presented in another paper.
Baumgartner, K. , Steenwerth, K.L. & Veilleux, L. 2008 Cover crop systems affect weed communities in a California vineyard Weed Sci. 56 596 605
Bugg, R.L. , McGourty, G. , Sarrantonio, M. , Lanini, W.T. & Bartolucci, R. 1996 Comparison of 32 cover crops in an organic vineyard on the North Coast of California Biol. Agr. Hort. 13 63 81
Costello, M.J. & Daane, K.M. 2003 Spider and leafhopper (Erythroneura spp.) response to vineyard ground cover Environ. Entomol. 32 1085 1098
Elmore, C.L. , Donaldson, D.R. & Smith, R.J. 1998 Weed management 107 112 Ingels C. , Bugg R.L. , McGourty G.T. & Christensen L.P. Cover cropping in vineyards: A growers handbook University of California Division of Agriculture and Natural Resources Oakland, CA
Gulick, S.H. , Grimes, D.W. , Munk, D.S. & Goldhammer, D.A. 1994 Cover-crop-enhanced water infiltration of a slowly permeable fine sandy loam Soil Sci. Soc. Amer. J. 58 1539 1546
Ingels, C.A. 1998 Implementation of cover cropping in vineyards: Grower practices 135 150 Ingels C. , Bugg R.L. , McGourty G.T. & Christensen L.P. Cover cropping in vineyards: A growers handbook University of California Division of Agriculture and Natural Resources Oakland, CA
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Ingels, C.A. 1998 Implementation of cover cropping in vineyards: Grower practices 135 150 Ingels C. Bugg R.L. McGourty G.T. Christensen L.P. University of California Division of Agriculture and Natural Resources Oakland, CA
Ingels, C.A. , Bugg, R.L. & Thomas, F.L. 1998 Vineyard cover crops and their uses: Cover crop species and descriptions 8 26 Ingels C. , Bugg R.L. , McGourty G.T. & Christensen L.P. Cover cropping in vineyards: A growers handbook University of California Division of Agriculture and Natural Resources Oakland, CA
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Ingels, C.A. Bugg, R.L. Thomas, F.L. 1998 Vineyard cover crops and their uses: Cover crop species and descriptions 8 26 Ingels C. Bugg R.L. McGourty G.T. Christensen L.P. University of California Division of Agriculture and Natural Resources Oakland, CA
Ingels, C.A. , Scow, K.M. , Whisson, D.A. & Drenovsky, R.E. 2005 Effects of cover crops on grapevines, yield, juice composition, soil microbial ecology, and gopher activity Amer. J. Enol. Viticult. 56 19 29
Norton, M.R. , Lelièvre, F. , Fukai, S. & Volaire, F. 2008 Measurement of summer dormancy in temperate perennial pasture grasses Aust. J. Agr. Res. 59 498 509
Norton, M.R. , Lelievre, F. & Volaire, F. 2006 Summer dormancy in Dactylis glomerata L., the influence of season of sowing and a simulated mid-summer storm on two contrasting cultivars Aust. J. Agr. Res. 57 565 575
Prichard, T.L. , Sills, W.M. , Asai, W.K. , Hendricks, L.C. & Elmore, C.L. 1989 Orchard water use and soil characteristics Calif. Agr. 43 23 25
USDA-NRCS 2008 Plants database US Department of Agriculture–Natural Resources Conservation Service Washington, DC 2 Nov. 2009 <http://plants.usda.gov/>.
Williams, L.E. , Phene, C.J. , Grimes, D.W. & Trout, T.J. 2003 Water use of mature Thompson Seedless grapevines in California Irrig. Sci. 22 11 18
Wolpert, J.A. , Phillips, P.A. , Striegler, R.K. , McKenry, M.V. & Foott, J.H. 1993 Berber orchardgrass tested as cover crop in commercial vineyard Calif. Agr. 47 23 25