WEED CONTROL IN A NEWLY ESTABLISHED
ORGANIC VINEYARD
By
CALLIE S. BOLTON
A thesis submitted in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE IN CROP SCIENCE
WASHINGTON STATE UNIVERSITY Department of Crop and Soil Sciences
May 2011
To the Faculty of Washington State University:
The members of the Committee appointed to the thesis of CALLIE SPENCER BOLTON find it satisfactory and recommend that it be accepted.
Chair, Timothy Miller, Ph.D.
Co-chair, Carol A. Miles, Ph.D.
Mercy A. Olmstead, Ph.D.
ii
ACKNOWLEDGMENTS
I am grateful for the funding provided by the Washington State University Center for
Sustainable Agriculture and Natural Resources and the Graduate Research Assistantship in the
Department of Crop and Soil Sciences. I am especially grateful to my committee for their guidance and support: Dr. Tim Miller, Dr. Carol Miles, and Dr. Mercy Olmstead. This project was also assisted by the technical support and guidance provided by Jacky King, Gary Moulton, and Jonathan Roozen.
iii
WEED CONTROL IN A NEWLY ESTABLISHED
ORGANIC VINEYARD
Abstract
By Callie S. Bolton, M.S. Washington State University May 2011
Chair: Richard T. Koenig
Environmental concerns regarding the impact of agriculture have created ever-growing pressure for growers to incorporate increasingly sustainable practices. Consumer demand for organic grape products, the major organic horticultural fruit crop worldwide, has led to growers seeking more information on organic grape production. Within organic grape production, weed management is the most critical issue with a newly established vineyard. In 2009, an organic vineyard was established to analyze the effectiveness of cover crops compared to tillage for weed control. Five treatments were applied to ‘Pinot noir précoce’ (PNP) and ‘Madeleine angevine’ (MA) grapes during the first two years of establishment. Weed control treatments were standard cultivation between-row and hand- weeding in-row (ST), in-row tillage with Wonder Weeder® and grass ((Lolium perenne L. and Festuca rubra L. ssp. arenaria ‘Osbeck’ F. Aresch.) cover crop seeded between-row (WW), winter wheat
(Triticum aestivum L. cv. ‘Otis’) cover crop and in-row string-trimming (W), Austrian winter pea (Pisum arvense L.) cover crop and in-row string-trimming (P), and wheat and pea cover crop mix and in-row string-trimming (W/P). Weed biomass in September 2009 was greater in the P treatment than under
ST and W. Weed biomass in July 2010 was greater in W, P, and W/P than in ST or WW. By
September, however, weed biomass was not different among treatments. Plot maintenance in ST
iv required more time than WW or the annual cover crop treatments. MA produced more shoot growth than PNP in September 2010. Grapevines under ST measured significantly longer than vines under any other treatment. Weed biomass was reduced by the wheat and pea cover crops, and the vine growth was also negatively affected by these cover crops. Wheat and pea did not differ in their level of competition with the weeds or the grapevines. Cultivation and hand weeding reduced weed biomass, but hand weeding required the greatest maintenance. In a newly established organic vineyard, the most effective and efficient management regime includes a vegetative-free zone in-row maintained using a specialty cultivator to minimize the need for hand weeding and a perennial cover crop in the alleyway to reduce weed biomass.
v TABLE OF CONTENTS
PAGE
ACKNOWLEDGEMENTS...... iii
ABSTRACT ...... iv
LIST OF TABLES...... x
LIST OF FIGURES ...... xii
CHAPTER 1 LITERATURE REVIEW ...... 1
1.1 Wine grape industry ...... 1
1.1.1 Organic wine grape production practices ...... 2
1.1.2 Economics of organic grape production ...... 4
1.1.3 Pacific Northwest wine grape industry...... 4
1.1.3.1 Grapevine selection...... 5
1.1.3.1.1 Rootstock ...... 6
1.1.3.1.2 Sources ...... 7
1.2 Organic vineyard establishment and maintenance...... 8
1.2.1 Climate ...... 9
1.2.2 Light...... 9
1.2.3 Topography...... 10
1.2.4 Soil tests...... 10
1.2.5 Trellising ...... 11
1.2.6 Training and pruning ...... 11
1.2.7 Plant nutrition ...... 12
1.2.8 Irrigation ...... 13
vi 1.2.9 Weed control...... 14
1.2.9.1 Cultivation ...... 15
1.2.9.1.1 In-row cultivation...... 15
1.2.9.1.2 Between-row cultivation ...... 17
1.2.9.2 Cover cropping...... 17
1.2.9.2.1 Legume cover crops ...... 18
1.2.9.2.2 Grass cover crops ...... 20
1.2.9.2.3 Combinations ...... 21
1.2.9.3 Mowing and string-trimming...... 22
1.3 Conclusions...... 23
1.4 References ...... 25
1.5 Tables...... 39
CHAPTER 2 ESTABLISHING AN ORGANIC VINEYARD IN
WASHINGTON STATE ...... 40
2.1 Introduction...... 40
2.2 Vineyard establishment ...... 42
2.2.1 Start up expenses...... 42
2.2.2 Vineyard site selection ...... 44
2.2.2.1 American Viticultural Areas (AVAs)...... 44
2.2.2.2 Topography ...... 44
2.2.2.3 Climate ...... 45
2.2.2.4 Light...... 46
2.2.2.5 Rainfall ...... 47
2.2.2.6 Soil ...... 48
2.2.3 Choosing grapevines ...... 50
2.2.3.1 Cultivars...... 51
vii 2.2.3.2 Rootstocks...... 51
2.3 Vineyard site preparation and maintenance ...... 54
2.3.1 Trellis system ...... 54
2.3.2 Fertilizer ...... 57
2.3.3 Irrigation ...... 60
2.3.4 Planting the grapevines ...... 61
2.3.5 Weed control...... 62
2.3.5.1 In-row...... 63
2.3.5.2 Between-row ...... 64
2.3.5.3 Cover crops ...... 65
2.3.6 Disease and insect pest control ...... 66
2.3.7 Pruning and training...... 68
2.4 Conclusions...... 70
2.5 References ...... 72
2.6 Tables...... 77
2.7 Figures ...... 79
CHAPTER 3 : WEED CONTROL IN A NEWLY ESTABLISHED ORGANIC
VINEYARD...... 81
3.1 Abstract ...... 81
3.2 Introduction...... 82
3.3 Materials and methods...... 84
3.3.1 Vineyard establishment...... 84
3.3.2 Climate ...... 86
3.3.3 Grapevines ...... 86
3.3.3.1 Irrigation ...... 87
3.3.3.2 Fertilizer...... 87
viii 3.3.3.3 Cover crop treatments...... 88
3.3.4 Vineyard maintenance ...... 89
3.3.5 Measurements...... 89
3.3.5.1 Shoot length...... 90
3.3.5.2 Shoot diameter ...... 90
3.3.5.3 Weed biomass ...... 90
3.3.5.4 Weed management ...... 91
3.3.6 Statistical analysis...... 91
3.4 Results ...... 91
3.4.1 Soil testing and amendments...... 91
3.4.2 Treatment effects on weed biomass distribution and composition in 2009 .... 92
3.4.3 Treatment effects on weed biomass distribution and composition in 2010 .... 93
3.4.4 Treatment effects on grapevine shoot growth in 2009 ...... 94
3.4.5 Treatment effects on grapevine shoot growth in 2010 ...... 94
3.4.6 Maintenance requirements ...... 95
3.5 Discussion ...... 95
3.5.1 Weed control...... 95
3.5.2 Grapevine growth...... 97
3.5.3 Maintenance...... 98
3.6 Conclusions...... 99
3.7 References ...... 101
3.8 Tables...... 108
3.9 Figures ...... 117
ix
LIST OF TABLES
PAGE
Table 1.1 Common legumes used as cover crops and their average N fixation rates ...... 39
Table 2.1 Line post options and features for organic vineyard establishment...... 77
Table 2.2 Specialized cultivators commonly used in vineyards ...... 78
Table 3.1 Soil analysis of organic vineyard prior to plant establishment at WSU Mount Vernon NWREC (2008) ...... 108
Table 3.2 Mean dry-weight biomass in organic weed control treatments between or within grapevines rows in 2009...... 109
Table 3.3 Mean dry-weight biomass of weeds between or within grapevine rows under five organic weed control treatments in 2010 ...... 110
Table 3.4 Mean dry weight biomass of white clover and other weeds within five organic weed control treatments in 2010 ...... 111
Table 3.5 Mean grapevine shoot length for five organic weed control treatments and two grapevine cultivars in 2009 ...... 112
Table 3.6 Mean grapevine shoot length for five organic weed control treatments and two grapevine cultivars in 2010 ...... 113
Table 3.7 Mean hours (h!p-1!ha-1) required for mowing, disking, Wonder Weeding (WW), hand weeding (HW), string-trimming (STR) and all season-long maintenance tasks (Total) for five organic weed control treatments and two grapevine cultivars in 2009...... 114
Table 3.8 Mean hours (h!p-1!ha-1) required for mowing, disking, Wonder Weeding (WW), hand weeding (HW), string-trimming (STR) and all season-long maintenance
x tasks (Total) for five organic weed control treatments and two grapevine cultivars in 2010...... 115
Table 3.9 Ranking of organic weed control treatments based on total weed biomass, grapevine shoot growth and maintenance time (2009 - 2010). Whole number rankings scaled were: 1 = superior and 5 = unacceptable...... 116
xi LIST OF FIGURES
PAGE
Figure 2.1 American viticultural areas in Washington State ...... 79
Figure 2.2 Irrigation manifold used at the WSU Mount Vernon NWREC organic vineyard showing components and direction of water flow ...... 80
Figure 3.1 Effect of weed control treatment on Madeleine angevine (MA) and Pinot noir précoce (PNP) grapevine shoot-growth on 30 July, 13 August, and 27 September in 2009 ...... 117
Figure 3.2 Effect of weed control treatment on Madeleine angevine (MA) and Pinot noir précoce (PNP) grapevine shoot-growth on 26 May, 3 and 23 June, 7 and 21 July, and 4 and 18 August in 2010 ...... 118
Figure 3.3 Mean weed and cover crop biomass in five organic weed control treatments in 2009 - 2010...... 119
Figure 3.4 Mean shoot lengths for organic weed control treatments and cultivars Madeleine angevine (MA) and Pinot noir précoce (PNP) on 27 September 2009 ...... 120
Figure 3.5 Three-way relationship between weed biomass, shoot growth, and maintenance time based on generalized results ...... 121
xii
CHAPTER 1. LITERATURE REVIEW
1.1 Wine grape industry
In 2008, organic vineyards spanned over 149,733 ha (370,000 A) worldwide, making up 2% of the world’s grape acreage and 29% of the world’s organic fruit acreage (Granatstein et al., 2010).
Currently, 4% of grape acreage in Washington is organically certified, a 22% increase since 2005
(Granatstein et al., 2010; Reeve et al., 2005). During the same time period, certified organic acreage grew by 67% nationally (Bair et al., 2008; USDA-ERS, 2005). Despite the increase in organic vineyard acreage, organic adoption is limited for small-scale growers who find organic agriculture regulations to be a barrier (Guthman, 2000). In contrast, large-scale growers tend to have larger operating budgets and technical support to help them understand and implement the organic regulations.
United States surveys indicate that 56-73% of consumers buy organic products on occasion (OTA,
2010) and in response manufacturers are increasing the integration of organic products into mainstream brand products. This increased use of organic ingredients produces a higher demand for organic raw materials, and this demand continues to grow as the public becomes more aware of the benefits of organic agriculture as it relates to human and environmental health (Goldfinger et al.,
2003; Tomera, 1999). A wider range of retailers selling organic products is emerging and domestic organic food sales in the U.S. have increased by 20% every year for the past 10 years (Willer and
Kilcher, 2009). In 2009 organic sales reached $26 billion, exceeding the expectations of producers
(OTA, 2010). A recent Organic Trade Association (OTA) survey indicated that 52% of food industry survey respondents experienced a restriction in market growth due to an inadequate supply of organic raw materials (Haumann, 2006).
The growing demand for organic grape products and ingredients has led to more research on organic grape production, quality, and marketing. Organic grape and wine production has become more efficient with higher quality and good marketability, and today, has attained a reputation of excellent quality and award winning taste (Geier, 2006). Most consumers believe that organic wines
! 1 are produced naturally and healthfully, which promotes the maximum amount of possible attributes and quality (Stolz and Schmid, 2008). As a result of increased sales and marketability, organic vineyards are becoming more profitable and less risky. Organic employment opportunities are also increasing in the organic production and marketing sectors overall (Haumann, 2006). To meet this employment demand, organic agriculture is becoming more of a focus in U.S. universities and increasingly curriculums are including organics (Haumann, 2006).
1.1.1 Organic wine grape production practices
Environmental concerns regarding the impact of agriculture, specifically increased soil erosion, decreased soil fertility, limited water supply, biodiversity loss, and herbicide resistance, have created ever-growing pressure for growers to incorporate increasingly sustainable practices (Krauss et al.,
2010; Lal et al., 2007; Montgomery, 2007; Triplett and Dick, 2008). Growers that market sustainable production practices maintain complex ecosystems. Possible modifications include minimizing fertilizer and irrigation inputs, reducing or eliminating tillage, and restricting pesticide use
(Huggins and Reganold, 2008; Krauss et al., 2010; Triplett and Dick, 2008). These modifications represent first steps in the development of more sustainable nutrient cycles and the management of diverse agro-ecosystems based on integrated pest and disease management. In addition, resource recycling within the agricultural system is beneficial when minimization of energy input and loss are desired. For example, addition of manure to the soil can increase soil biotic activity (García-Gil et al.,
2000), and planting cover crops and minimizing tillage help conserve soil organic matter and water within the cropping system (Brennan and Smith, 2005; Doran and Smith, 1991; Peacock et al.,
1991; Walser et al., 2007).
Many studies support the positive correlation between organic practices and sustainability
(Dabbert, 2003; Granatstein and Sanchez, 2009; Légère and Stevenson, 2002; Liebman and Dyck,
1993; Pacini et al., 2003; Raimbault and Vyn, 1991; Reeve et al., 2005; Stevenson et al., 1998).
Management practices affect multiple facets in sustainable and organic production systems and
! 2 success depends on the active awareness of all aspects of the ecosystem in addition to the economic well-being of the grower (Watson et al., 2002) Sustainable and organic systems focus on solutions that are beneficial to the surrounding ecosystem and will have effects that last for multiple years (Stockdale et al., 2001). Whether the grower is entirely devoted to organic production or farms both organically and conventionally, production goals include maintaining a well developed and fertile soil structure, maintaining high biological activity, and minimizing reliance on inorganic chemical use (Guthman, 2000; Madge, 2005).
Today, consumers are demanding wines that are produced in an environmentally friendly vineyard using sustainable practices and that taste good (Flexas et al., 2010). Correspondingly, sustainable practices in vineyards and organic wine production are increasing and more wine grape producers are taking steps to comply with regulations for organic certification. In 2007, more than 960 ha of vineyards in the United States were managed using sustainable practices with reliance on naturally derived pesticides and fertilizers and alternative methods for weed control (Hostetler et al., 2007).
An essential aspect of organic farming systems is the dependence on biological systems. Cover crops are frequently used in organic farming and can reduce soil erosion, increase biological activity, suppress weeds without the use of herbicides, and add nitrogen (N) back to the soil without separate inputs. Reganold et al. (2010) found that the use of leguminous crops in organic strawberry production systems resulted in fewer fungal rots, higher amounts of ascorbic acid (vitamin C) and increased antioxidant activity. An organic vineyard cover crop study showed increased populations in predatory insects and decreased populations in key pests such as leafhoppers and thrips (Nicholls et al., 2000). Organic practices like cover crops, composting, and no synthetic pesticide use have also resulted in less vine root damage in phylloxera-infested vineyards compared to conventionally managed vineyards (Lotter, 2000). However, growers often list apprehension towards managing weeds without herbicides as a key factor limiting their organic production (Bond and Grundy, 2001).
Further barriers to organic production include the need to consider soil fertility management across multiple seasons, and the need for crop rotations based on the specific crop environment and
! 3 conditions (Liebman and Davis, 2000).
1.1.2 Economics of organic grape production
Grapes can be successfully managed organically and produce grape qualities comparable to conventionally managed grapes; but organic practices require more inputs, more time for implementation, and have higher costs (Pimentel et al., 2005). A five-year study comparing inputs of five organic and conventional vineyards showed that organic grape production costs were 69-91% higher, mainly for weed control, and the key to economic success in organic grape production was through price premiums (White, 1996). In organic vineyards, weed control is the highest cost out of all necessary inputs, especially during the establishment phase, and is the most technically challenging production practice (Dufour, 2006; Guthman, 2000). If weeds are not controlled adequately yields can be reduced by 5-35% (White, 1996).
1.1.3 Pacific Northwest wine grape production
In the last seventeen years, the Pacific Northwest (PNW), which includes Washington, Oregon, and
Idaho, has developed into a wine grape (Vitis vinifera) growing region second only in U.S. production to California (USDA-NASS, 2011). The recent expansion in wine grape production has raised the PNW to comparable levels to the premier wine grape growing regions of France, Spain, Italy, Australia, and
Argentina (OIV, 2010). In 2010, 5% of the nation’s grapes were produced in Washington and wine grapes accounted for 78% of the revenue from grapes (USDA-NASS, 2011). From 2008 to 2009, wine grape tonnage increased by 8% in Washington. In 2009, a record 156 thousand tons of wine grapes were produced, and the value was $813-$1200 per ton resulting in Washington’s highest grape revenue in history (USDA-NASS, 2010). Wine grapes return more income per hectare than table grapes, illuminating why more than half of Washington’s 24,280 grape hectares (60,000 A) are for wine production (USDA-NASS, 2010).
The vast majority (99%) of wine grapes in Washington are planted on the eastern (inland) side of the Cascade Mountains, where the hot, dry summers, long days, well-drained soils, and scattered
! 4 south-facing slopes create optimal conditions for growing premium wine grapes (Clore et al., 1972;
Nagel et al., 1972). Cultivars such as Syrah, Merlot, Chardonnay, Cabernet Franc, and Cabernet
Sauvignon are popular for eastern Washington (Nagel et al., 1972). Only one of the 11 American viticultural areas (AVAs) in Washington is located west of the Cascade Mountains, the Puget Sound
AVA. In 2008, approximately 1% of Washington’s grapes were planted in the Puget Sound AVA
(USDA-NASS, 2007). This amounted to 75 ha (184 A) of wine grapes with an additional 50 ha (123
A) planned for the near future (Moulton, 2009).
Western Washington is exposed to prevailing northwestern marine winds that create cool, moist summers. Southwestern winds during the winter generate mild and wet conditions with temperatures rarely dropping below freezing. Although western Washington provides a less typical premium-wine grape production climate, and production is minor compared to the eastern inland region, recent success with cool-climate cultivars (e.g., Pinot noir, Siegerrebe, and Gewürztraminer) has led to increased production.
1.1.3.1 Grapevine selection
Grapes (Vitis sp.) are a temperate climate crop originating in the Middle East near the Fertile
Crescent. While wine grapes are grown worldwide, they cannot survive extreme and rapid drops in temperatures, especially below -23°C (-10 °F), and today they are grown predominantly between the
30th and 50th latitude. Successful vineyards grow grape cultivars that maximize growth and produce a high quality wine given specific site characteristics, meso-climate and resources. Cultivars appropriate for western Washington only require 1600 growing degree-days (GDDs) (base temperature of 50 °F) or less to ripen fruit. Madeleine angevine (V. vinifera: Malingre précoce x
Madeleine royale) is a French, white wine cultivar that has been grown in western Washington for 25 years because it only requires 1600 GDDs for fruit ripening and production (Moulton and King,
2005). Pinot noir (V. vinifera) is a highly recognized cultivar originating in the Burgundy region of
France that is also popular for Washington (Moulton and King, 2005). Cultivation of Pinot noir began
! 5 as early as the Gauls at the time of the Roman conquest, circa 300 B.C. The Roman agriculturist
Columella described Pinot noir in his prose-style book De Re Rustica (c. 70 A.D.) as such: “it can be distinguished by its leaf, rounder than the others because its wine keeps to a great age and because it is the only one whose fertility does justice to the soil, even the poorest.” Pinot noir has shown extreme resistance to cold winters, however due to its early bud-break, it tends to be vulnerable to frost (Galet and Smith, 1998). Pinot noir précoce is a natural mutation of Pinot noir, which ripens two weeks earlier, a positive attribute for cooler climates such as western Washington. Other popular cultivars for western Washington are Garanoir and Siegerrebe (Moulton and King, 2005).
1.1.3.1.1 Rootstock
Most Washington vineyards include self-rooted vines, however grafted plants can provide advantages depending on soil characteristics, local climate, pests, scion cultivar, specific use of grapes (i.e. wine or table grapes), target quality, and desired training method (Galet and Smith,
1998; Van Huyssteen et al., 1984). Rootstocks are used primarily to hasten ripening, advance maturity, and provide resistance to phylloxera and tolerance to lime. Phylloxera, a root-affecting insect originating in American vineyards, was introduced to Europe in the mid-1800s and subsequently, French cultivars were grafted onto phylloxera-resistant American rootstocks (Galet and
Smith, 1998). In eastern Washington, the majority of vineyards are self-rooted since the climate provides optimum growing conditions for wine production. Phylloxera infested V. labrusca are present in eastern Washington, however infested V. vinifera plants have been removed from vineyards and the sandy soils common to the region reduce phylloxera infestation (Folwell et al.,
2001). State regulations also prevent importation of material from non-certified out-of-state nurseries, such as rooted plants from Oregon where phylloxera is still present. In western
Washington, grapevines are often grafted to rootstocks that promote early ripening, a desirable attribute for areas with limited GDDs.
A popular rootstock for western Washington currently is Couderc 3309 (3309 C), a hybrid of
! 6 Riparia tomentiux and Rupestris martin. Couderc 3309 was the second most propagated rootstock in French nurseries until 1968 and presently is the third most commonly used rootstock in France, accounting for 13.5% of all grafts and having 307 ha (758 A) of planted parent vines (Galet and
Smith, 1998). An estimated 101,000 ha (250,000 A) of vines in France are grafted to 3309 C rootstocks. This rootstock is preferred in many French and Mediterranean regions due to its phylloxera-resistance, induction of earlier ripening and maturation, vigorous growth, and ease of rooting and grafting. Couderc 3309 is moderately vigorous and well suited to close spacing, however it is somewhat limited by its medium lime-tolerance (11%-according to the Drouineau-Galet index), sensitivity to all species of root-knot nematodes (Meloidogyne spp.), and latent viruses depending on which scion it is grafted to (Galet and Smith, 1998; Wolpert and Anderson, 2005). Research has shown that Pinot noir scions grafted to 3309 C rootstock ripened earlier and yielded juice with higher
Brix, lower titratable acid, and higher pH than self-rooted vines, which are all positive attributes for winemaking (Moulton and King, 2005). Other rootstocks that had similar results evaluated in this study included Millardet et de Grasset 101-14 and Millardet et de Grasset 420A. Millardet et de
Grasset 101-14 has been reported to have higher fruit yields, a larger volume of structural wood, and shallower root growth than 3309 C, when grafted with Pinot noir scions (Candolfi-Vasconcelos et al., 1994).
1.1.3.1.2 Sources
Newly planted vines will readily show the effects of poor cultivation and nursery management so a reliable graft source is important. A study examining the association between nursery stock quality and the decline of young vines in California found the most common cause of poor performance of young vines was physical defects present in the vines at the time of planting (Stamp, 2001). Nursery- induced stress can be detrimental to vine health after planting, possibly inhibiting vineyard establishment and vine maturation. Some examples of stress factors originating at the nursery include: rootstock shaft lesions at the basal disbudding site and/or improperly healed graft unions;
! 7 inadequate root systems and other physical defects; stress from extended cold storage or excessive time in containers; and disease pathogens (Stamp, 2001). Petri disease, or Young Vine Decline
(YVD), is the decline in health of a young vine due to fungal pathogens of Phaeoacremonium and
Phaeomoniella species (Scheck et al., 1998). Fortunately, YVD incidence is less prevalent today and is less of a problem for nurseries and vineyards in Washington State (Judkins, pers. comm.;
Thornton, pers. comm.).
A vine that is grafted in late winter and is slowly acclimated to outdoor conditions, or hardened, in time for spring or early summer planting is called a ‘green’ graft, and is currently the most common grafting method used in vineyards in western Washington (Thornton, pers. comm.). Alternatively, dormant grafts are grafted in late winter, grown at the nursery for the summer, and are planted the following dormant/winter season. Some Californian nurseries grow grafted vines in the field until dormancy, then sell the vines as ‘1-year field grown plants’ (Thornton, pers. comm.). Increasing in popularity is ‘potted grafts’, where the grafts are transferred to larger pots and grown at the nursery through the summer. The lengthened hardening period allows nurseries to make these grafts available all year long for planting (Thornton, pers. comm.).
1.2 Organic vineyard establishment and maintenance
Organic certification requires that no prohibited substances were used in the vineyard for at least three years prior to certification. There are only a limited number of organic pesticides available to growers; therefore, organic vineyards are designed to minimize inputs and the need for inputs and management interventions (Lanini et al, 1994). A vineyard’s location and design directly correlate with potential pest threats as well as future management requirements (Madge, 2005). Selection of the vineyard site requires consideration of climate, topography, and soil characteristics.
During the establishment years, vineyard maintenance includes supplying water and nutrients at appropriate levels, controlling weeds, and training the vines to the trellis system. Grape production can potentially begin in the third or fourth year. At this point, berry diseases can develop and insects
! 8 can become pests, therefore preventative efforts are added to vineyard maintenance regimes. In producing vineyards, added efforts will be needed for fruit quality control and harvest.
1.2.1 Climate
Climate is a major distinguishing factor between geographic regions and influences the levels of insect pest, disease, and weed pressures (Madge, 2005). Meso-climate, the climatic conditions of the specific vineyard site, must be considered, as a site may have frost pockets or high wind exposure, which can injure the grapevines making them more susceptible to pests and diseases as well as limiting their growth. Additionally, heavy or frequent precipitation (>40 in. annually) can lead to greater incidence of fungal diseases and weeds (Smith, 2002).
1.2.2 Light
Growing grapevines in western Washington and most other regions requires management efforts to maximize light exposure, whereas in viticultural areas such as eastern Washington the management regime protects vines from overexposure to sunlight through canopy manipulation
(Olmstead et al., 2006). In July, a south-facing slope in western Washington (e.g., Seattle area) receives around 7 kilowatt-hours!meter-2!day (kWh!m-2!d), while a south-facing slope in eastern
Washington (e.g., Yakima area) receives 10-14 kWh!m-2!d, the highest in the U.S. (NREL, 2011).
Sugar production and accumulation in the grape is a major goal for wine-grape growers, and is directly related to the amount of light the vine receives (Olmstead et al., 2006; Smart, 1986). In grapevines, 30-40% of full sunlight, or at least 800 µmol!m-2s (7.2 kWh!m-2!d at 550 nanometers), is required for maximum sugar production (Smart, 1988). Photosynthetic processes only utilize light ranging from 400-700 nanometers, also called photosynthetically active radiation (PAR), and the most efficient wavelength, or the most intensely absorbed, is 550 nanometers (Smart, 1985). The outer leaves of the canopy generally absorb at least 85% of the total PAR, depending on canopy structure, and the inner leaf layers absorb only about 10% of the PAR (Smart, 1985). Vineyards suffering from inadequate light exposure experience decreased fruit set, delayed fruit maturity,
! 9 reduced fruit color, reduced acid degradation, reduced fruit cluster initiation for subsequent seasons, increased disease incidence (e.g., powdery mildew), and increased insect pest populations
(e.g., leafhoppers) (Betigga et al., 1989; Buttrose, 1968; Downey et al., 2006; Emmett et al., 1992;
Kliewer, 1970; Smart, 1986).
1.2.3 Topography
Topographic characteristics of an area that are pertinent to vineyard site selection include elevation, slope, and aspect. Elevation influences air temperatures by creating thermal inversion events caused by the movement of colder, denser air downhill displacing the less dense, warmer air, causing it to move uphill. This creates a warm belt found at certain elevations that is conducive to good vine health and growth (Kurtural, 2007). Every 304 m (1,000 ft) of elevation increase above the warm belt is associated with a 3°C (3.6°F) decrease in temperature (Kurtural, 2007). Low-lying areas where cold air drains is considered a potential frost pocket and vines are not typically planted here (Kurtural, 2007).
A slope of 5-10% allows cold air to drain downhill but is modest enough to allow safe equipment travel and operation (Kurtural, 2007). The aspect, or compass direction the slope faces, correlates with the amount of direct sunlight that hits the slope and the vines, and also the amount of GDDs that accumulate over the growing season. In the northern hemisphere, a southern exposure receives the most light during the growing season. Earlier bud-break occurs in vineyards with southern or western aspects, compared to northern aspects, and warming in the spring occurs sooner due to warmer afternoon temperatures (Kurtural, 2007). Row orientation also affects sunlight exposure and air circulation due to vines shading adjacent vines or blocking wind.
1.2.4 Soil tests
Soil composition is comprised of soil texture, organic matter, water content, and chemical constituents. Soil texture and organic matter examinations provide key information regarding possible inhabitability by phylloxera and nematode populations (McKenry et al., 2001), however
! 10 specific bioassays are essential for definitive evaluation of the presence of these pests. Soil water content is affected by the regional climate as well as soil texture and porosity, and is a basic but essential analysis. Drought conditions can severely damage newly planted vines, but waterlogged soil leads to root asphyxia or conditions conducive to root rot (Galet and Smith, 1998).
The chemical analysis of the soil sample provides information in regards to possible nutrient deficiencies or toxicities. Soil pH is an important soil characteristic as it not only directly impacts plant health but can also impact the availability of macro- and micronutrients for vine growth even if they are present in the soil. Optimum macronutrient (e.g., nitrogen, phosphorous, potassium, sulfur, etc.) and micronutrient (e.g., molybdenum, magnesium, boron, iron, etc.) levels are essential for success of newly planted grapevines. A soil analysis includes these elements and will provide the amounts of nutrients to be applied prior to planting (Galet and Smith, 1998). Soil composition can vary significantly in a field therefore 15 to 20 soil subsamples, at 0.3-0.6 meter depth (1-2 ft), will more adequately represent the entire planting area (Hart et al., 2003).
1.2.5 Trellising
Construction of a trellis system for an organic vineyard differs from a conventional vineyard primarily in the choice of materials used for end posts. Posts can be composed of wood, metal, plastic, or concrete, and combinations, however organic regulations do not permit end posts that are treated with prohibited preservatives. Indigenous tree species such as western Juniper (Juniperous occidentalis) and Pacific Yew (Taxus brevifolia) have been used as untreated posts and can remain durable for more than 30 years (Morrell et al., 1999). Additional support for young grapevines is provided by 3-ft stakes made from material such as bamboo or non-treated metal, placed adjacent to each grapevine.
1.2.6 Training and pruning
Grapevine training consists of manipulating the trunk and canopy to maximize resource allocation for fruit production, maximize air circulation to minimize disease pressure, and minimize labor efforts
! 11 (Bravdo and Naor, 1995; Jordan, 1981; Smart, 1985). Increasing the canopy’s surface area in low light areas (e.g., western Washington) by dividing the canopy or retaining leaves, increases sunlight absorption, while a vineyard planted on a steep slope that is subjected to high velocity winds (e.g.,
Columbia Basin) needs a decreased canopy surface area in order to minimize wind damage.
In general, the vertical shoot positioning (VSP) training system, where the vine shoots are positioned upright, maximizes canopy light penetration and air circulation and is recommended for western Washington (Gladstone and Dokoozlian, 2003). Eastern Washington solar radiation levels are much higher than in western Washington, therefore training efforts are made to protect exposed fruit from burning. Fertile soils and high water availability can cause vines to grow too vigorously, resulting in undesirable fruit composition or fruit exposure. In these circumstances a training system such as the Scott-Henry that minimizes vine vigor is better suited (Gladstone and Dokoozlian, 2003;
Henry, 1990; Reynolds and Vanden Heuvel, 2009). A general guideline for maximizing light exposure is a 1:1 ratio of trellis height to row width (Smart et al., 1982).
In some climates, nutrients, water, or light are not limiting factors to high-quality grape production, and shoot pruning or leaf thinning is not needed to balance vine growth with the available resources
(Smart, 1985). Canopy manipulation or leaf pruning can decrease the incidence of diseases such as
Botrytis Bunch Rot, a fungal disorder (Botrytis cinerea) that develops in grape clusters lacking air circulation (Bettiga et al., 1989; English et al., 1990; Gubler et al., 1987). In organic vineyards, removing leaves around the grape cluster exposes it to drying conditions and decreases Botrytis potential.
1.2.7 Plant nutrition
Compost and manure applications are commonly used as organic pre-plant fertilizers due to their relative low cost and diverse nutrient content including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (I), and other trace elements (Cogger and Sullivan, 2001; Cogger et al., 2002;
Hirschfelt, 1998; Ingels et al., 2005; Peterson et al., 1995; Pinamonti, 1998; Walser et al., 2007).
! 12 Compost can be composed of yard trimmings (e.g., sawdust, wood-chips, corn stalks, grass, spoiled hay, tree and shrub prunings) animal manure, and/or municipal waste (i.e., fruit and vegetable waste), and the exact composition can vary between batches or by year due to changes in garden species, food consumption, precipitation, temperature, or animal nutrition (Cogger et al., 2002;
Cogger and Sullivan, 2009; Peterson et al., 1995). In general, most pre-plant fertilizer applications include amendments of nitrogen, potassium, and phosphorous (Bavaresco et al., 2010; Janssen,
2011; Mullins, 1992; Robinson, 2005; Walser et al., 2007; Winkler et al., 1974). Micronutrient additions are minimal in order to avoid toxic affects from over application.
The high expense of organic fertilizer has lead to a reliance on cover crops, manure and compost by the majority of organic growers (Hirschfelt, 1998; Ingels et al., 2005; Pinamonti, 1998; Walser et al., 2007; Watson et al., 2002). Cover crops, specifically legumes, are N sources while grass cover crops can prevent N leaching and improve efficiency (Rinnofner et al., 2008). For example, an annual rye grass cover crop along with a single application of manure resulted in an increase in nutrient utilization in comparison to no cover crop, due to the ability of the rye grass to scavenge unused N and store it in the root-zone for grapevine uptake later (Reeve et al., 2005).
1.2.8 Irrigation
An irrigation system is typically installed prior to planting to water newly planted grapevines. There are two main types of vineyard irrigation, drip and sprinkler. Today, 80-90% of new vineyards utilize drip irrigation (O’Neal-Coates, 2003). Under drip irrigation, water is deposited in the grapevine rooting area at lower rates than for sprinkler, improving efficiency (Guthman, 2000). In addition, drip irrigation reduces water available for weed growth between rows, which is of special significance to organic growers who find weed control a primary barrier to organic production. In contrast, sprinkler irrigation systems are available as micro or overhead sprayers. They increase the water availability to weeds and foliar moisture, which encourages some fungal diseases like Eutypa dieback (Eutypa armeniacae), black rot (Guignardia bidwellii), Phomopsis leaf spot (Phomopsis viticola), and powdery
! 13 mildew (Erysiphe necator) (Dufour, 2006).
Young vines, especially newly grafted vines, are extremely sensitive to water stress, therefore irrigation is beneficial until the vines’ root systems have developed (Araujo et al., 1995). Irrigation also provides some frost protection to vulnerable young vines (Zabadal and Andresen, 1997).
Established vineyards do not require supplemental irrigation if rainfall is frequent and temperatures are mild enough to limit evapotranspiration (avg. <24°C), unless the soil has low-water holding capacity. Studies in western Washington show that irrigated vineyards can be fully productive sooner than non-irrigated vineyards and could develop more uniformly, suggesting that irrigation is valuable
(Moulton and King, 2005).
Mature vines are more resilient to water stress conditions because of their increased storage capacity for nutrients and water, therefore, less irrigation is needed (Pradubsek, 2008; Smart and
Coombe, 1983). Deficit irrigation is used to control berry size and vegetative growth (Chaves et al.,
2007; O’Neal-Coates, 2003; Matthews et al., 1987; Matthews and Anderson, 1988; McCarthy,
2002; Wample and Smithyman, 2002). Vine stress through water restriction during berry development and fruit ripening produces smaller grapes and allows for increased concentrations of sugar and other desirable wine grape constituents like titratable acid and anthocyanins (O’Neal-
Coates, 2003; Pellegrino et al., 2004; Seguin, 1983). Restricting water also reduces fruit set and foliage production, increasing sun exposure and improving flavors (Chaves et al., 2007; McCarthy et al., 2002; Wample and Smithyman, 2002).
1.2.9 Weed control
Weeds compete with grapevines for water, nutrients, and light, slowing their growth. Young vines have not yet developed reserves for water or nutrients, and so are especially susceptible to weed competition (Elmore and Donaldson, 1999). Consequences of insufficient weed control can be delayed grape production, and subsequent delayed income for the grower (Madge, 2005). There are few effective and affordable tools available to organic growers for controlling weeds; hand weeding is
! 14 effective but expensive due to labor costs (Bond and Grundy, 2001; Krauss et al., 2010; Lanini and
Hoddle, 2000; Peigné et al., 2007; Teasdale et al., 2007). Organic herbicides are not as efficient nor are they as cheap as conventional herbicides. As a result, many growers use conventional herbicides during the establishment years and convert to organic when grapes are produced and three years after the last application of a prohibited substance.
Weed pressures can be reduced prior to planting the grapevines by cultivation and/or seeding a cover crop to outcompete or smother the weeds (Porter, 1998; Sullivan et al., 2003). Perennial weeds can be the most problematic in vineyards, and scouting plus spot-treatments if necessary prior to planting the grapevines can promote better establishment and make future weed control easier (Madge, 2005). In western Washington, common perennial weeds include common dandelion
(Taraxacum officinale, Weber, T. Densleonis, Desf; Leontodon taraxacum, L.), Canada thistle
(Cirsium arvense L.), stinging nettle (Urtica dioica L.), field bindweed (Convolvulus arvensis L.), field horsetail (Equisetum arvense L.), and quackgrass (Elymus repens L. Gould).
1.2.9.1 Cultivation
Cultivation involves the use of a mechanical device to cut, uproot, or bury weeds and is highly effective at controlling annual weed species. A disadvantage of cultivation is that it can cause soil compaction and deplete organic matter. Additionally, breaking up roots and reproductive structures of persistent perennial weed types spreads the rhizomes, tubers, or seeds throughout the soil enabling these weeds to re-establish and re-infest at high frequencies (Houser, 1962; Madge, 2005).
Frequent cultivation can lead to organic matter depletion and soil erosion, which can significantly reduce the sustainability and lifetime of a vineyard (Pool et al., 1993). Water drainage capacity in the alleyways can also be reduced by soil compaction caused by equipment (Madge, 2005).
1.2.9.1.1 In-row cultivation
Grapevine roots absorb nutrients and water primarily under the vines or the in-row area
(Pradubsuk, 2008); therefore in-row weed growth can most negatively affect vine growth. The in-row
! 15 area tends to be inhabited by the most vigorous, durable and competitive weeds (Pool et al., 1993).
As a result, many strategies exist for in-row weed control. Although there are varying recommendations for the allowable amount of undervine vegetation, for optimal growth of a newly established vineyard, complete elimination of in-row weeds is the most effective option (Dufour,
2006).
Due to the close proximity of the weeds to fragile vine roots, specialty cultivators that are designed for narrow spaces and easy maneuvering around vine trunks, posts, and irrigation risers are essential (Dufour, 2006; Madge, 2005). Such equipment, widely used today in organic vineyards throughout the world, is mounted with a manual or automatic retractable arm that is moved by the operator or triggered by a solid object (Dufour, 2006; Sweet and Schreiner, 2010). Some cultivators will have different depth settings to enable the operator to select an appropriate depth to avoid accidental root and vine damage and cultivate at high speeds (Madge, 2005). Some examples of specialized tillage equipment include the French plow, otherwise known as a grape hoe, the Weed
Badger (Weed Badger Division, Marion, ND) and the Wonder Weeder (Harris Manufacturing,
Burbank, WA), which has an articulating swing-arm with rotary harrow and disk attachments (Dufour,
2006). Its touch sensitive ‘shear bar’ is positioned before the cultivators and is extended far enough so that it contacts the vine-trunk before the cultivators do. Contact signals the cultivators to swing around the vine trunk and continue in-row cultivation between the vines. These specialty cultivators can be mounted on the side, rear, or front of tractors depending upon the tractor mounting system.
In-row cultivators have a wide range of costs and styles and are not all suited for every cropping system (Wise et al., 2007). Additionally, not all vegetation is reached with mechanical devices, thus occasional hand weeding helps to maintain clean in-row areas, especially around the vines and posts. Hand weeding can be costly because it is labor intensive and time-consuming, however, growers can become more intimate with the grapevine’s health and growing conditions and learn the weed patterns and soil conditions of the vineyard, leading to increased efficacy of other management practices (Madge, 2005). Organically approved contact herbicides, propane fueled
! 16 weed burners, mulch, or less competitive cover crops have additional costs and inconsistent proof of efficacy, and further research is needed to show benefits (Hostetler et al., 2007).
1.2.9.1.2 Between-row cultivation
Between-row (alleyway) cultivation effectively removes unwanted vegetation and is highly effective at minimizing weed competition with the grapevines. However, maintaining low vegetation levels typically requires multiple cultivation passes during the growing season, increasing costs, erosion potential, soil compaction, and vine root damage potential (Baumgartner et al., 2003; Laikam, 1965;
McConnell, 2003; McGonigle et al., 1990; Pool et al., 1993). While alleyways are relatively easy to cultivate, many growers are questioning its necessity and are exploring the use of cover-cropped alleyways to suppress weeds (Tesic et al., 2007; Van Huyssteen and Weber, 1980).
1.2.9.2 Cover cropping
Cover cropping is a method of weed control widely used in both organic and conventional vineyards worldwide and was reported as the best option for alleyway soil management in Australia (Dastgheib and Frampton, 2000; Liebman and Davis, 2000; Pardini et al., 2002; Porter, 1998). Increasing sustainable practices is a major purpose for the utilization of cover crops in organic systems
(Lampkin, 2005; Langdale et al., 1991). Cover crops can increase soil organic matter, decrease the need for fertilizers through inherent nutrient additions (i.e. legumes fixing N), reduce pH and macronutrient leaching (especially nitrate), and increase soil-microbial life (Davies et al., 2001;
Hansen and Djurhuus, 1997; Ingels et al., 2005; Nevens and Reheul, 2002; Tan and Crabtree,
1990). Cover crops also reduce the need for soil cultivation, consequently reducing erosion potential, soil compaction and surface crusting, and improving soil porosity and machinery movement (Gulick et al., 1994; Hogue and Neilsen, 1987; Langdale et al., 1991; Lu et al., 2000;
Pardini et al., 2002; Rinnofner et al., 2008; Tan and Crabtree, 1990). In vineyards where water is not limiting, cover crops can suppress weeds and reduce excessive vine growth (Tesic et al., 2007; Van
Huyssteen and Weber, 1980). In an established vineyard, cover crops can be planted in-row as a
! 17 vine vigor reducer, which can improve berry quality (Celette et al., 2005, 2009; Tesic et al., 2007). In vineyards with a limited water supply, cover crops in-row and in alleyways compete for water and nutrients with the grapevines and reduce yields. Alleyway cultivation is more commonly utilized in dry land conditions or when sprinkler irrigation is used (Tesic et al., 2007; Van Huyssteen and Weber,
1980).
The effectiveness of a specific cover crop species is influenced by climate, soil quality and texture, topography, vine density, rootstock and scion cultivars, training system, and trellis structure (Pardini et al., 2002). The cover crop’s life cycle and physiology also contribute to weed suppression. Annual cover crops are more easily maintained, but are less competitive. Perennial cover crops are less easily controlled, but are better competitors against hardy annual and perennial weeds. Drip-irrigated vineyards require drought tolerant cover crop species such as forage legumes, grasses, and some forbs (herbaceous flowering plants) for adequate weed suppression (Clark, 2007; Olmstead et al.,
2001).
Appropriate soil preparation is necessary to establish a cover crop (Porter, 1998). Coordinating the seeding depth with the seed size and seedling vigor, and reducing weed populations by tillage prior to seeding, increases a cover crop’s efficacy (Porter, 1998). For example, small seeded grasses have low initial seedling vigor and so require a shallow seeding depth (0-1.3 cm), whereas large seeded peas do best with a deeper seeding depth (4-8 cm) due to their more vigorous growth and susceptibility to seedling desiccation when left too close to the surface. Also, seeding at uniform depths can be affected by unlevel and littered soil surfaces (Porter, 1998).
1.2.9.2.1 Legume cover crops
Legume cover crops are commonly utilized for their N-fixing attributes and can reduce fertilizer costs (Doran and Smith, 1991; Wells, 2011). Legumes vary in their rate of N-fixation and many potential rates have been identified for specific forages, pulses and oilseeds (Table 1). The rate of N- fixation is influenced by the legume’s physiology, the type of Rhizobium (i.e. bacterial strain) that it is
! 18 inoculated with, and the planting conditions (i.e. soil pH, organic matter, temperature, and water content) (Blum et al., 1997; Doran and Smith, 1991; Power and Zachariassen, 1993). For example, field pea (Pisum sativum L. var. Century), faba bean (Vicia faba L. var. Outlook), hairy vetch (Vicia vollosa Roth var. Madison), sweetclover (Melilotus alba L. ‘common white’), crimson clover (Trifolium incarnatum L. ‘Kentucky’) and white clover (Trifolium repens L. ‘Merit’) have optimum N-fixation at soil temperatures of 10 °C (Power and Zachariassen, 1993). In contrast, soybean (Glycine max L.
Merr. ‘Harsoy’) and Korean lespedeza (Lespedeza stipulacea Maxim.‘Climax’) have optimum N- fixation at soil temperatures of 20 °C. While N-fixation rates for most legume crops typically range from 7-36 kg!ha-1, under perfect conditions maximum N-fixation can be as high as 91 kg!ha-1 of N
(Sullivan and Diver, 2003).
In a living-mulch system (legume cover crop is mowed) only 40-60% of the fixed N is available for crop uptake (Sullivan and Diver, 2003). For example, if hairy vetch (Vicia villosa L.) accumulates a total of 36 kg of N!ha-1, then only 18-21 kg N!ha-1 will be available to subsequent crops (Bair et al.,
2008; Bugg et al., 1996; Sullivan and Diver, 2003). Examples of annual legumes commonly used as cover crops are subterranean clover (Trifolium subterraneum L.), rose clover (T. hirtum L.), crimson clover (T. incarnatum L.), red clover (T. pratense L.), berseem clover (T. alexandrinum L), and burr medic (Medicago polymorpha) (Blum et al., 1997).
Mowing or tilling the legume is essential for mineralization of fixed N. Mowing is used to control cover crop growth in no-till management to reduce soil erosion and fuel costs. Mowing results in top and sloughed off root legume biomass being available for decomposition and N mineralization
(Ingels et al., 1994). When both mowing and tillage are performed, the mineralization rate is maximized and N can be available in two to three weeks (Doran and Smith, 1991; McGourty, 2004).
The optimum timing for mowing and tillage depends on the overall objectives. For example, to allow annual legumes to reseed, they are typically mowed in the spring and early summer (Fourie, 2005;
McGourty, 2004).
! 19 1.2.9.2.2 Grass cover crops
Grass cover crops have large, strong root systems that help to reduce soil erosion, increase soil organic matter from residual biomass, and reduce vine vigor through competition. Decomposing grass residue increases soil organic matter and N, leading to increased nitrogen, potassium, and pH, especially if the clippings are incorporated into the soil (Ripoche et al, 2011; Snapp and Borden,
2005). Grass roots also improve soil porosity, consequently increasing water penetration and drainage (Blake, 1991; Bugg et al., 1996; Morlat and Jacquet, 2003). The stubble of mowed grass cover crops also allows for greater solar radiation absorption by the soil, reduces dust, and provides traction for equipment (Bugg et al., 1996; Gaffney and Van Der Grinten, 1991; Olmstead, 2006).
Grasses have a high carbon (C) to N ratio, tying up N in the soil after incorporation so that it is not readily available to the grapevines (Celette et al., 2009; Coppens et al., 2006; Mary et al., 1996;
McKell et al., 1969; Olmstead, 2006). Grass cover crops are better suited to fertile sites where they decrease vine vigor by competing for soil N (Brandi-Dohrn et al., 1997; Ingels et al., 1994; Karraker,
1950; Martinez and Guiraud, 1990; McGourty, 2004; McKell et al., 1969; Meisinger et a., 1991;
Morgan et al., 1942; Sattell et al., 1999). Grass cover crops have different degrees of competitiveness. For example, hard fescue, creeping red fescue, and sheep fescues (all commonly referred to as fine fescues) are considered the least competitive because of their short stature. Rye grass and tall fescues, typically used as turf, are moderately competitive due to their slightly taller stature, and require one to two mowings per year (McGourty, 2004). Rye grass has been shown to have less impact on vine size and water consumption, and maintained high grape yield as compared to more vigorous cover crops, and is therefore widely used (McKell and Duncan, 1969; Pool et al.,
1993; Tan and Crabtree, 1990).
Self-reseeding grass cover crops, like ‘Midmar’ annual ryegrass (Lolium multiflorum Lamark)
(Fourie, 2005), ‘Blando’ brome (Bromis mollis L.) and ‘Zorro’ fescue (Vulpia myuros L. C.C. Gmel.), are well suited to vineyards where erosion is probable and a no-till regime is implemented
(McGourty, 2004). However, tall cover crops can increase the risk for frost damage to young vines,
! 20 interfere with air circulation and block sunlight from reaching grape leaves leading to Botrytis outbreaks. Additionally, grasses typically begin their growth earlier in the season than grapevines, potentially giving the grasses a competitive advantage and affecting future vine growth for multiple years (Celette et al., 2009). Grapevine roots compensate by developing deeper root systems than the cover crop, where additional water and leached N may be available (Celette et al., 2008). To reduce these risks, cover crops are cut to a maximum of 18 in. height at the time of grapevine bud break (McGourty, 2004).
There are many grass cover crops suited to vineyards, especially where soil water content and nutrients are not limiting. In western Washington, wheat (Triticum aestivum L.) and annual ryegrass
(Lolium multiflorum L.) are frequently utilized. In western Oregon, mixtures of winter annuals, clovers, native grasses, native meadow plants, perennial grass and clover cover crops had minimal impact on the vine’s growth compared to clean cultivation (Sweet and Schreiner, 2010). Sweet and Schreiner
(2010) showed at vineyard sites with natural high soil nutrient and water levels, it is possible to establish a high vigor grass cover crop without negatively affecting grapevine growth. When perennial grasses and perennial broadleaf species dominate the weed composition, a permanent perennial cover crop species may be most beneficial (Sanguankeo et al., 2009).
1.2.9.2.3 Combinations
Benefits from a combination of grass and legume cover crops include increased N availability from the legume and increased soil organic matter and nutrient recycling from the grass. In areas of high climatic variability, several species are planted to ensure that at least one will grow to provide ground cover. After mowing, degradation is relatively quick if the mixture consists of mostly legumes, whereas mixtures that are predominantly grasses are generally longer lasting due to their higher C to
N ratio (Dufour, 2006). A cover crop composed of native species generally reseeds itself readily and is well adapted to the local environment. Frequency and timing of mowing tends to favor the strongest competing species in the mixture and eventually eliminates the weaker species (Pool et al.,
! 21 1993). Cover crop mixtures are most effective when the species are chosen based on residing soil characteristics, potential pest problems, climatic conditions, and native vegetation. Since conditions vary by location and time, it may be difficult to initially choose a cover crop mixture best suited to a particular vineyard. The succession of a highly mixed cover crop will lead to a stand of one or a few species that are the most competitive and longest-lived in that environment (Dufour, 2006).
1.2.9.3 Mowing and string-trimming
Vegetative alleyways require a maintenance regime that includes managing plant height to minimize reseeding by weeds or annual cover crops. Mowing does not disturb the soil and is easily adjusted to achieve objectives (height and timing) (Madge, 2005). Typically, a cover cropped alleyway is mowed one to four times each growing season (Sweet and Schreiner, 2010; Tesic et al.,
2007). Another strategy is to mow only every other alleyway to suppress competition, maintain low vine vigor and reduce soil compaction or disturbance (Pardini et al., 2002); but this is only used in relatively dry areas with low or moderate cover crop growth. The timing of mowing is based on the plant growth and the effect on grapevine vigor. In general, highly vigorous plants are mowed more often than low vigor plants. If weed removal is desired, they are mowed below their regeneration point (Gago et al., 2007). High mowing (8-10 inches) can keep medium to tall broadleaf weeds short while allowing legumes to regenerate, and low mowing (1-2 inches) can remove a large number of species, but tends to favor grasses due to their physiologically lower regeneration point (Madge,
2005). The mowed cuttings are used as mulch and a nutrient source when left in the alleyways or thrown into the vine row (McGourty, 2004). An increased mowing frequency increases labor and fuel costs, however, the possible loss of production due to excessive competition with the grape vine can result in much more substantial economic losses (Pardini et al., 2002).
Although organic management of vineyard floors typically involves in-row tillage and alleyway mowing or light cultivation (Hostetler et al., 2007), new tools are currently being used in some commercial vineyards that allow mowing under the trellis (Wise et al., 2007). These tools are tractor
! 22 or ATV mounted with small side decks that pivot around vine trunks, cutting weeds as close as several in. above the soil surface (Wise et al., 2007).
1.3 Conclusions
Newly planted grapevines have minimal nutrient reserves (Elmore and Donaldson, 1999); therefore, adequate fertilization and minimal competition are vital during the establishment years. In organic vineyards, manure, compost, organically certified fertilizers, and legume cover crops can be a source of N and other nutrients. Greater efficiency in nutrient utilization by the grapevines can occur if weeds are simultaneously kept at low competitive levels and if the nutrients are kept in the root-zone for a longer period of time. Grass cover crops can smother weeds, reducing their growth, and grass residue can release recycled nutrients back into the root-zone after decomposition and mineralization. Legume cover crops can accumulate N through N-fixation, which can lead to reduced fertilizer costs. However, N availability may not be for several months or longer after planting the cover crop, and once it is available weeds can utilize the N as well.
Weed competition can most negatively affect vine growth during the establishment period due to the high susceptibility of young grapevines to competition for light, nutrients and water since they do not have well-established root systems (Elmore and Donaldson, 1999). Newly planted grapevines do not have water and nutrient reserves available for use during the first spring, consequently, first-year grapevine growth is based solely on nutrient and water applications during the first growing season.
Cover crops plus mechanical methods (e.g., in-row cultivation, mowing) have been shown to be the most effective at suppressing annual weeds in an organic vineyard (Porter, 1998; Sullivan et al.,
2003). However, it is unclear whether combinations are more effective than separate efforts. Hand weeding is effective, however the time requirements make this a limited option and more efficient methods are needed. Specialty cultivators are available and allow for quick weed control in the vine rows, however the efficacy of specific cultivators is unknown.
During the establishment phase of an organic vineyard, the most expensive and important
! 23 management task is weed control. It is essential to understand the affects of different cover crops and mechanical devices on young grapevines as well as their weed suppression efficacy. To hasten vineyard revenue during grape production, it is vital to reduce the time-span of the non-producing or establishment phase of the vineyard. More information is needed on the efficacy of organic methods of controlling weeds in newly established vineyards.
! 24
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! 38 1.5 Tables
Table 1.1 Common legumes used as cover crops and their average N fixation rates (Clark, 2003;
Heichel et al., 1985; Peoples et al., 1995).
Potential Rate of N-Fixation (kg- y
Common Name Scientific Name z Life-Cycle N!ha-1)
Lucerne/alfalfa Medicago sativa L. 15-386 CSP
Vetch Vicia sativa L. 0-106 WA, CSA
Winter pea Pisum sativum L. 3-244 WA
Chickpea Cicer arietinum L. 1-141 SA
Common bean Phaseolus vulgaris L. 0-20 SA
White clover Trifolium repens L. 9-291 LP, WA
Red clover T. pratense L. 11-373 SP, B
Strand medic M. littoralis L. 52-102 SP, SA
Subterranean clover T. subterraneum L. 2-206 CSA
Berseem clover T. alexandrinum L. 13-39 SA, WA
Crimson clover T. incarnatum L. 12-185 WA, SA
Sweetclover Melilotus spp. 13-31 B, SA
Hairy vetch Vicia villosa L. 16-28 WA, CSA
Medics Medicago spp. 9-22 SP, SA
Cowpeas Vigna unguiculata L. Walp. 9-201 SA
Pisum sativum spp. arvense Field pea 16-183 WA L.
Vicia villosa ssp. dasycarpa Woollypod vetch 18-46 CSA Roth.
Birdsfoot trefoil Lotus cornicuatus L. 49-109 LP z ! The range is the amount of N2 fixed by the legume species annually. yWA = winter annual, SA = summer annual, CSA = cool-season annual, SP = short-lived perennial, LP
= long-lived perennial, B = biennial.
! 39 CHAPTER 2. ESTABLISHING AN ORGANIC VINEYARD IN WASHINGTON STATE
2.1 Introduction
In the last seventeen years, Washington State has developed into a wine grape- (Vitis vinifera L.) growing region that is second only in U.S. production to California (O’Neal-Coates, 2003; Washington
Wine Commission, 2010). Currently, grapes are ranked 10th in Washington State for overall crop value, and Washington received the second highest revenue from grapes in the country ($201 million) (USDA-NASS, 2009). Of wine grapes produced in Washington, 99.5% are planted on the eastern (inland) side of the Cascade Mountains, where the climate is considered optimum for premium wine grape production. Western Washington provides a less typical premium-wine grape production climate but recent success with cool-climate cultivars (i.e. Pinot noir, Siegerrebe, and
Gewürztraminer) and close proximity to consumers has led to increased interest in production in the maritime region.
Within the last decade there has been a shift towards sustainable cropping systems due to consumer demand for high quality wines that are produced in an environmentally friendly fashion
(Flexas et al., 2010). As of 2008, organic vineyards span over 150,000 ha (370,000 A) worldwide, making up 2% of the world’s grape acreage and 29% of the world’s organic fruit acreage
(Granatstein et al., 2010). In recent years the demand for organic wine grapes has increased. A
2006 market review showed that the organic wine market grew by 10-15% as compared to 2005
(Richter and Padel, 2007). In 2007, more than 810 ha (2,000 A) of vineyards in the U.S. were managed organically and did not use synthetic products, but instead relied on naturally derived pesticides and fertilizers and alternative methods for weed control (Hostetler et al., 2007). Currently,
4% of grape acreage in Washington is organically certified, a 22% increase since 2005 (Granatstein et al., 2010; Reeve et al., 2005). During the same time period, certified organic acreage grew by
67% nationally (Bair et al., 2008; USDA-ERS, 2005). Today, organic wine has attained a reputation of excellent quality and award winning taste (Geier, 2006).
! 40 The growing demand for organic wine has led to an increased demand for efficient and cost effective organic grape production systems. Organic vineyards tend to have higher costs during the establishment years than conventional vineyards (White, 1996); therefore it is very important that growers consider their management options with short-term as well as long-term costs in mind.
Organic certification requires complete records of all vineyard supplies and applications. Also required is an historical record of land use and applications for three years prior to certification. Only organic-compliant materials, including posts, fertilizer and pesticides, may be used in a certified organic vineyard. Growers are encouraged to review organic certification regulations with their certifier prior to establishing a vineyard.
This publication will discuss the primary steps for establishing an organic vineyard and will provide some specific examples based on our experience of establishing a 2.5-acre organic vineyard at
Washington State University. Resource information is provided for each topic as much has been written about wine grape production and readers are encouraged to review this information for more in-depth information.
Resource Information:
Dufour, Rex. 2006. Grapes: organic production. National Sustainable Agriculture Information
Service. http://Appropriate Tech. Transfer Rural Areas (ATTRA). Nat. Ctr. Appropriate Tech.
(NCAT).org/attra-pub/grapes.html
Hoheisel, G., T. Ball, M.A. Olmstead, and N. Rayapati. Vine to wine: successfully establishing a
vineyard and winery (DVD). https://pubs.wsu.edu/ItemDetail.aspx?ReturnTo=0&ProductID
=15409
Madge, David. 2007. Organic viticulture: an Australian manual. Department of Primary Industries
in Irymple, Victoria, Primary Industries Research. http://www.dpi.vic.gov.au/DPI/nrenfa.nsf
/9e58661e880ba9e44a256c640023eb2e/9e81d00a9e71d90dca2573ae001242ca/$F
ILE/Part1.pdf
! 41 Moulton, Gary. 1997. Growing grapes for wine and table in the Puget Sound region. Washington
State University Extension Publication EB0775. http://cru.cahe.wsu.edu/CEPublications
/eb0775/eb0775.html
Moulton, G and J. King. 2005. Growing wine grapes in maritime western Washington. Washington
State University Extension Publication. EB2001. https://pubs.WSUe
du/ItemDetail.aspx?ProductID=13959&SeriesCode=&CategoryID=137&Keyword
Sood, Tara. 2008. Sustainable agriculture: organic grape production. University of Lincoln,
Nebraska. http://cari.unl.edu/SustainableAg/organicgrapeproduction.html.
! 2.2 Vineyard establishment
2.2.1 Start up expenses
Before establishing your vineyard, list expected costs, which will include:
• Land – purchase or lease
• Water utilization - public or private
• Grapevines – purchase costs of grafted or non-grafted vines, shipment costs
• Machinery – purchasing or renting for site preparation and management (cultivator, disk, ATV,
truck, mower, trencher, etc.)
• Fuel – usage, storage
• Irrigation – equipment and supplies, including shipment costs (pipe, filter, backflow prevention
device, pressure reducer, drip-line or sprinkler heads, fertilizer injector, etc.)
• Trellising – supplies including shipment costs (end posts, line posts, wire, planting stakes,
anchors, cable, crimps, wood drill, etc.), purchasing or renting equipment (auger, post hole
digger, etc)
• Labor wages
For more information regarding business planning and associated costs for establishing a vineyard
! 42 please see resources below. While only a few of these publications are specific to organic wine grapes, they all present information that applies to all vineyard operations.
Resource Information:
Ball, T., R. Folwell, J. Watson, and M. Keller. 2003. Wine grape establishment and production
costs in Washington. Washington State University Cooperative Extension and U.S. Dept. of
Agriculture. EB1955. http://cru.cahe.wsu.edu/CEPublications/eb1955/EB1955.pdf
Ball, T., R. Folwell, J. Watson, and M. Keller. 2004. Establishment and annual production costs for
Washington Concord grapes. Washington State University Cooperative Extension and U.S.
Dept. of Agriculture. EB1965. http://cru.cahe.wsu.edu/CEPublications/eb1965/eb19
65.pdf
Folwell, R.J., B.D. Gebers, R. Wample, A.F. Aegerter, and T. Bales. 2003. Production and
marketing risks associated with wine grapes in Washington. Washington State University
Cooperative Extension and U.S. Dept. of Agriculture. XB0977e. http://cru.cahe.wsu.edu/
CEPublications/xb0997e/xb0997e.pdf
Julian, J.W., C.F. Seavert, C. Kaiser, and P.A. Skinkis. 2009. Establishing and producing Cabernet
sauvignon wine grapes in western Oregon. Oregon State Unversity Extension Bulletin.
EM8974-E. http://arec.oregonstate.edu/oaeb/files/pdf/ EM8974-E.pdf
Julian, J.W., C.F. Seavert, P.A. Skinkis, P. VanBuskirk, and S. Castagnoli. 2008. Establishing and
producing Pinot noir wine grapes in western Oregon. Oregon State Unversity Extension
Bulletin. EM8969. http://wine.oregonstate.edu/files/ files/ EM8969E%5B1%5D%
20Economics%20of%20Vineyard%20Establishment%20W%20OR%202008.pdf
Klonsky, K., L. Tourte, and C. Ingels. 1992. Sample costs to produce Organic Wine Grapes on the
North Coast with an annually sown cover crop. University of California, Davis Cooperative
Extension and SAREP. http://www.sarep.ucdavis.edu/ pubs/costs/92/grape1.htm
Washington Wine Industry Foundation. 2006. Business plan: checklist. VineWise.
! 43 http://www.vinewise.org/files/documents/Business_Plan.pdf
Washington Wine Industry Foundation. 2006. Vineyard establishment: checklist. VineWise.
http://www.vinewise.org/files/documents/Vineyard_Establishment_ FINAL.pdf
Washington Wine Industry Foundation and U.S. Dept. Agr. 2011. Cost of production calculators for
wine and juice grapes. http://www.nwgrapecalculators.org/
! 2.2.2 Vineyard site selection
2.2.2.1 American Viticultural Areas (AVAs)
Currently, there are eleven American Viticultural Areas (AVAs) in Washington State (Figure 2.1).
Each AVA consists of a designated geographical area, and vineyards that produce wine or grapes from within those areas are permitted to include the AVA name on their label. Consumers associate the AVA on the label with certain flavors, grape varieties, and wine quality. Washington’s AVAs are each unique and are individually recognized by consumers, some more so than others. Before choosing your site and grapevine cultivars, research popular Washington AVAs and their current grape production prices.
2.2.2.2 Topography
Elevation, slope and aspect are topographic characteristics that are important to vineyard site selection. Elevation influences air temperatures due to thermal inversion events caused by the movement of colder, denser air downhill displacing the less dense, warmer air, causing it to move uphill. This creates a warm belt found at certain elevations that are relative to the elevation. Identify the elevation of the warm belt in the area you are interested in and plant the grapevines around this elevation. Every 1000 ft.of elevation increase above the warm belt is associated with a 3.6°F decrease in temperature. The low-lying areas where the cold air drains is a potential frost pocket and can cause frost damage to vines (Kurtural, 2010).
Slope, measured as a percentage of elevation change over horizontal distance, affects the
! 44 drainage of colder air downhill. Plant the vines on a slope of 5-10% to allow cold air drainage and safe equipment travel and operation (Kurtural, 2010). The slope’s aspect, that is the compass direction it faces, affects the amount of direct sunlight that hits the slope and the vines (see Light), and also the number of growing degree-days (GDDs) that accumulate over the growing season (see
Climate). Plant on a slope with a southern exposure for optimum sunlight absorption, however if this is not possible a western-facing slope can promote earlier warming in the spring due to warmer afternoon temperatures and thus could be chosen. Earlier bud-break occurs in vineyards with southern or western aspects, compared to northern aspects, and warming in the spring occurs sooner due to warmer afternoon temperatures (Kurtural, 2007).
Resource Information:
Ahmedullah, M., and J. Watson. 1985. Site selection for grapes in eastern Washington.
Washington State University Extension Bulletin EB1358. https://pubs.WSUedu/
ItemDetail.aspx?ProductID=13558&SeriesCode=&CategoryID=137&Keyword
Washington Wine Industry Foundation. 2006. Vineyard site selection: checklist. VineWise.
http://www.vinewise.org/files/documents/Vineyard_Site_Selection__FINAL.pdf
2.2.2.3 Climate
Grapes are a temperate crop customarily grown between the 30th and 50th latitudes. Most varieties cannot tolerate temperatures below -15 °C (5 °F), and 90% of AVAs are located where the average temperature during the growing season is 15-21 °C (62-70 °F) (Jones et al., 2010). Grape growth and development is strongly influenced by GDDs, which is calculated using the following equation:
(maximum temperature + minimum temperature) － base temperature (10 °C or 50 °F) 2
! 45 The grape plant is only actively growing when the average daily temperature is above the base temperature of 10 °C (50 °F), thus, the rate of growth depends on the number of GDDs – the more
GDDs, the faster the growth. Across the Pacific Northwest, the range of GDDs is 1600-3300. The
Western Regional Climate Center website (http://www.wrcc.dri.edu/), includes 220 weather stations throughout Washington State, and provides current and historical data (including GDD accumulation) for all these stations; the Washington State University’s Agricultural Weather Network website
(http://www.weather.wsu.edu/) also provides similar data.
When selecting a cultivar, one of the most critical limitations will be GDD accumulation. There are a limited number of cultivars that will produce quality wine at the lower end of the GDD range (< 1700
GDD) characteristic of western Washington, however eastern Washington provides near optimum conditions in most areas. Therefore selecting a cultivar for eastern Washington is not nearly as limited as for western Washington. For more information regarding cultivars and their associated optimal GDD range, refer to Reisch et al. (1993), and for information on grape varieties best suited for western Washington, refer to Moulton and King (2005).
2.2.2.4 Light
Grape vines thrive when they receive direct sunlight for at least 2-3 hours a day during the growing season, from April 1 through October 31. Growing grapevines in western Washington and most other regions requires management efforts to maximize light exposure, whereas in inland desert areas
(e.g., eastern Washington) the management strategy must include techniques to protect vines from sunburn through canopy manipulation (Spayd et al., 2002). In July, a south-facing slope in western
Washington (e.g., Seattle area) receives around 7 kilowatt-hours!meter-2!day (kWh!m-2!d-1), while a south-facing slope in eastern Washington (e.g., Yakima area) receives 10-14 kWh!m-2!d-1, the highest in the U.S. (NREL, 2011). Sugar production and accumulation in the grape is the primary focus, and is directly related to the amount of light the vine receives (Olmstead et al., 2006; Smart, 1986). In grapevines, 30-40% of full sunlight, or at least 800 µmol!m-2s (7.2 kWh!m-2!d-1 at 550 nm), is
! 46 required for maximum sugar production (Smart, 1988). Photosynthetic processes only utilize light ranging from 400-700 nm, also called photosynthetically active radiation (PAR), and the most efficient wavelength, or the most intensely absorbed, is 550 nanometers (Smart, 1985). The canopy structure dictates how and where this PAR is absorbed by the plant. The outer leaves of the canopy generally absorb at least 85% of the total PAR, depending on canopy structure, and the inner leaf layers absorb only about 10% of the PAR (Smart, 1985).
Vineyards suffering from inadequate light exposure demonstrate symptoms such as decreased fruit set, delayed fruit maturity, reduced fruit color, reduced acid degradation, reduced fruit cluster initiation for subsequent seasons, increased disease incidence (e.g., powdery mildew), and increased insect pest populations (e.g., leafhoppers) (Dry et al., 2000).
2.2.2.5 Rainfall
In areas of high precipitation (> 1000 mm), a vineyard is more susceptible to fungal infestations and diseases. Good air filtration can help alleviate disease pressures in areas of higher summer rainfall, and air filtration is best on a sloping hillside or near bodies of water. There are only a limited number of effective organic pesticides, so select a site that does not receive excessive summer rainfall. Another effect of heavy rainfall can be soil saturation, especially in areas with poorly drained soil or high water tables. Fertilizer should not be applied during likely times of soil saturation, or heavy precipitation, since this can lead to surface run-off and possible water pollution. In eastern WA the average annual rainfall is 130-380 mm (5-15 in.), soil saturation is not generally a problem and the emphasis is on selecting a site with adequate irrigation.
Resource Information:
University of Washington, Department of Atmospheric Sciences. 2011. Average monthly
temperatures for Washington State. http://www.atmos.washington.edu/
marka/wa.normals.html
Washington State University. 2011. Washington agricultural weather network.
! 47 http://weather.WSUedu/
Western Regional Climate Center. 2011. Climate information. http://www.wrcc.dri.edu/
2.2.2.6 Soil
Before planting your vineyard, test the soil to determine its characteristics and nutrient levels.
Collect soil from different locations within the site so that the samples accurately portray the entire planting area. Soil composition can vary significantly over distances as close as 15.2 m (50 ft).
Therefore several samples may be needed so the soil test represents the entire planting area. For each soil sample, 15 to 20 subsamples should be collected (Hart, 1995). The soil analysis will provide information regarding possible nutrient deficiencies or toxicities. Essential nutrients for healthy grape production include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), boron
(B), magnesium (Mg), copper (Cu), sulfur (S), manganese (Mn), and iron (Fe). Soil pH is an important soil characteristic as it not only directly impacts plant health but can also impact availability of nutrients even if they are present in the soil. The soil analysis should include all these elements and will be used to determine the amounts of nutrients or lime (to increase soil pH) to apply (Galet,
1998). For information on interpreting the soil analysis, refer to the Vine Nutrition section at the WSU
Viticulture and Enology Research and Extension website (wine.wsu.edu/research-extension/grape- growing/).
The depth of the soil and the presence of hard pans or mineral compaction layers, such as Caliche, should also be determined. Shallow soils (less than 0.9 – 1.2 m deep) may not allow for adequate grapevine root growth. If a hardpan or compaction layer is present in the selected site, break it up using deep tillage devices (e.g., chisel plow) before you proceed with vineyard establishment. Soil texture and organic matter can provide key information regarding potential issues with phylloxera
(Daktulosphaera vitifoliae Fitch) and nematodes (i.e. root-knot Meloidogyne spp. and dagger
Xiphinema spp.) (McKenry, 2001), however for definitive evaluation of the presence of these pests,
! 48 specific bioassays are essential and can be provided by certified testing laboratories. Washington
State University’s Pest Management Resource Services provides a listing of laboratories and their services. Use soil pest assays to determine if vines require grafting to a resistant rootstock (Galet,
1998). Soil water holding capacity is affected by the regional climate, and is another essential analysis. Drought conditions can severely damage newly planted vines, but waterlogged soil leads to root asphyxia or root rot.
Resource Information:
Dow, A.I., and M. Ahmedullah. 1981. Soil fertility and nutrient management of Washington
vineyards. Washington State University Extension Bulletin 0874. http://wine.wsu.edu/
research-extension/files/2010/05/soil-fertility.pdf
Irrigated Agriculture Research & Extension Center. 2011. Nematodes of Grapes in Washington
State. Washington State University. http://www.prosser.wsu.edu/ faculty/riga/Riga-
index.html
Nail, W.R. 2005. Critical issues with early vineyard establishment. Connecticut Agricultural
Experiment Station. New England Vegetable and Fruit Conference (NEVFC).
www.newenglandvfc.org/pdf.../earlyvineyard_establishment.pdf
Nicholls, C.I., M.A. Altieri, A. Dezanet, M. Lana, and D. Feistauer. 2004. A rapid, farmer-friendly
agroecological method to estimate soil quality and crop health in vineyard systems. Bio-
dynamics: a periodical furthering soil conservation and increased fertility in order to
improve nutrition and health. 250:33-40. http://wine.wsu.edu/ research-
extension/files/2010/05/vineyard-crop-and-soil-indicators.pdf
United States Department of Agriculture National Resource Conservation Service. 2011. Soil
survey for Washington State. http://websoilsurvey.nrcs.usda.gov/app/
Washington State University. 2011. Analytical laboratories and consultants serving agriculture in
the Pacific Northwest. http://www.puyallup.wsu.edu/analyticallabs/services/
! 49 Washington Wine Industry Foundation. 2006. Soil and site properties: checklist. VineWise.
http://www.vinewise.org/files/documents/Soil_and_Site_Properties_ FINAL.pdf
! 2.2.3 Choosing grapevines
Grapes can be self-rooted or grafted to a rootstock, depending on the grower’s needs, preference or budget. In western Washington, grapevines can be grafted to rootstocks that promote early ripening which is desirable due to fewer GDDs in the area. The majority of grapevines in eastern
Washington are self-rooted since the climate provides optimum growing conditions for wine production, so altering the vines’ characteristics (i.e. earlier ripening by grafting to rootstock) is not necessary. In many grape-producing regions, the primary reason grapes are grafted is to control phylloxera. In the Pacific Northwest, phylloxera-infested Vitis vinifera plants have been removed in eastern Washington and the sandy soil that is typical in that region prevents phylloxera infestation
(Folwell et al., 2001). Phylloxera has not yet been found in western Washington, and statewide regulations prevent out-of-state material, such as rootstocks from Oregon where phylloxera is still present, from entering Washington.
Select a grapevine supplier that is reliable and has a respectable reputation as determined by previous clientele experience. Grapevines from a local nursery will spend less time in transport and will likely have less vine damage caused by prolonged exposure and/or handling. In a study in
California, the most common cause of poor performance of young grapevines was physical defects present in the vines at the time of planting (Stamp, 2001). Nursery-induced stress can inhibit vineyard establishment, and therefore vine maturation. Some examples of stress factors originating at the nursery include: rootstock shaft lesions developed from the basal disbudding site and/or improperly healed graft unions; inadequate root systems and other physical defects; limited carbohydrate reserves; stress from extended cold storage or excessive time in containers; and Petri disease pathogens (Stamp, 2001). Petri disease, also referred to as Young Vine Decline (YVD), is caused by Phaeoacremonium and Phaeomoniella fungal species (Scheck et al., 1998). There are
! 50 few organic options for treating disease or deficiencies, so it is very important to start with clean, healthy and strong vines.
Orders for non-grafted and green-grafted grapevines should be placed by the end of February for planting the same year. However, orders for dormant grapevines, grafted or self-rooted, should be placed at least 18 months in advance. There is no maximum order for grapevines, however most nurseries require a minimum order of 25 vines. A ‘green graft’ or ‘green bench graft’ is currently a popular grafting method because it requires less time to produce. The vine is grafted in late winter
(February – March) and is ready to plant in May. A dormant graft is grafted in late winter and is ready to plant 12 months later during the following dormant/winter season. In California, some nurseries will graft in late winter, grow the grafted vines in the field that growing season, and then sell the vines as ‘1-year field grown plants’. A less common grafting method that is increasing in popularity is a ‘potted graft’, which is similar to a ‘green graft’ but grown into the summer in a larger container.
The lengthened hardening period allows nurseries to make these grafts available all year long.
2.2.3.1 Cultivars
Choose a cultivar based on climate features (i.e. cool-climate or hot, arid-climate) and based on your preference to produce for a particular type of wine. It is important to keep in mind that the growing environment will ultimately determine which wine grapes to plant. There are many cultivars available for most climate zones. Galet (1998) has described the characteristics of many cultivars and rootstocks currently being used by wine grape growers throughout the U.S. in his book Grapevine
Varieties and Rootstock Varieties. For more information regarding cultivars and their associated optimal GDD range, refer to Reisch et al. (1993), and for information on grape varieties best suited for western Washington, refer to Moulton and King (2005). Additionally, visit local vineyards to see which cultivars do well in your area, and ask your local extension agent for variety recommendations.
2.2.3.2 Rootstocks
Considerations for rootstock choice include soil characteristics, local climate, scion cultivar,
! 51 specific use of grapes produced (i.e. wine production or table grapes), target quality, and desired training method (Galet, 1998). Some rootstocks promote earlier ripening which can be extremely beneficial in areas with low GDDs like western Washington. Resistant rootstocks are highly recommended in areas with phylloxera infestation. Rootstocks can also provide lime tolerance, which can boost vine growth and production if this is an issue at the site. There are fewer organic treatment options for insect pests and diseases so prevention is generally the best protection method, therefore grafting may be worth the extra cost.
A popular rootstock currently used in western Washington is Couderc 3309, also referred to as
Couderc 3309, and is a cross between Riparia tomentiux x Rupestris martin. Until 1968, Couderc
3309 was the second most propagated rootstock in French nurseries and today is the third most commonly used rootstock. This rootstock is popular throughout the Mediterranean region due to its phylloxera-resistance, induction of earlier ripening and maturation, moderately vigorous growth, and ease of rooting and grafting. Couderc 3309 has also been described as being well suited to close spacing (Wolpert, 2005). However, Couderc 3309 is somewhat limited by its medium tolerance for active lime (11% according to the Drouineau-Galet index), sensitivity to all species of root-knot nematodes (Meloidogyne spp.), and latent viruses depending on which scion it is grafted to (Galet,
1998; Wolpert, 2005). Refer to Galet (1998) for descriptions of rootstocks used by grape growers throughout the U.S.
Resource Information:
Delate, K., and A. McKern. 2006. Evaluation for grape varieties for certified organic production –
Neely-Kinyon trial. Iowa State Agron. Extension report. http://
extension.agron.iastate.edu/organicag/researchreports/nk05grape.pdf
Moulton, G. and J. King. 2005. Growing wine grapes in maritime western Washington. Washington
State University Extension Bulletin EB2001. http://cru.cahe.WSUedu/
CEPublications/eb2001/eb2001.pdf
! 52 Moulton, G.A., J. King, L.J. Price, R.S. Darland and T.R. Bronkema. 2002. Annual report: evaluation
of wine grape cultivars and selections for a cool maritime climate. Washington State
University Northwest Research and Extension Center. http://extension.wsu.edu/maritime
fruit/reports/Pages/WineGrapes02.aspx
National Organic Program. 2011. Database on NOSB recommendations for materials considered
for use in organic agricultural production and handling. United States Department of
Agriculture. Excel spreadsheet. http://www.ams.usda.gov/AMSv1.0/getfile?dDoc
Name=STELDEV3100278&acct=nopgeninfo
O’Neal-Coates, S. 2003. Crop profile for wine grapes in Washington. 2003. Washington State
University Cooperative Extension Bulletin MISC0371E. http://wine.wsu.edu/research-
extension/files/2010/05/crop-profile.pdf
Olmstead, M.A. and M. Keller. 2007. Chip bud grafting in Washington state vineyards. Washington
State University Extension Bulletin EB2023E. https://pubs.wsu.edu/
ItemDetail.aspx?ProductID=13980&SeriesCode=&CategoryID=137&Keyword=
Reisch, B.I., R.M. Pool, D.V. Peterson, M.H. Martens, and T. Henick-Kling. 1993. Wine and juice
grape varieties for cool climates. New York State Agricultural Experiment Station, College of
Agriculture and Life Sciences, Cornell University Bulletin.http://www.nysaes.cornell.edu/
hort/faculty/reisch/bulletin/wine/
Washington State Dept. of Agriculture Organic Food Program. 2009. Seed and planting stock
guidelines. Fact sheet AGR3000. http://agr.wa.gov/FoodAnimal/Organic
/docs/3000_seed_planting_stock_factsht_8.09.pdf
Zabadal, T.J. 2002. Growing table grapes in a temperate climate. Michigan State University
Extension, Department of Horticulture. Extension Bulletin E2774.
http://web2.msue.msu.edu/bulletins/Bulletin/PDF/E2774.pdf
!
! 53 2.3 Vineyard site preparation and maintenance
2.3.1 Trellis system
Grapevines are supported on a trellis to maximize leaf light exposure, support the weight of the grapevine when it has a full fruit load, and support the vine high enough above the ground to increase air circulation and compete against floor vegetation. End posts provide the main support for the grape vines, and are the most costly component of a vineyard trellis system due to the strength and size needed to construct a long-lasting trellis system. Construction of a trellis system for an organic vineyard differs from a conventional vineyard primarily in the choice of materials used for end posts. The U.S. National Organic Program (NOP) standards prohibit the use of wood treated with copper-chromium-arsenate (CCA) or other prohibited materials (e.g., creosote). Treated wood in existing trellis systems that are certified to National Organic Standards (NOS) is allowed, but replacement wood must not be treated.
For an organic system, posts can be of wood, steel, plastic, concrete or a combination. Steel and concrete posts have low load-bearing capacity, are more likely to cause damage to machinery and are usually used only for line posts. Plastic posts are also weak, having only 10% the same load- bearing capacity of wood posts, however recently innovated recycled plastic posts have demonstrated adequate performance in a cool climate vineyard, but not in a hot climate vineyard where the heat reduces the rigidity of the plastic. Some positive aspects of using recycled plastic are its termite, rot, and corrosion resistance characteristics and the reduction in amount of plastic entering landfills. Untreated timber is currently the best option for end post material due to its durability. Different tree species and wood types (i.e. heartwood, sapwood, softwood, hardwood) have different strengths and durability. Sapwood should not be used unless it is treated with a preservative, however most preservatives are not permitted for organic systems. Heartwood is the most durable, and is recommended despite its increased expense.
Tree species types that produce naturally durable wood include Western Juniper (Juniperus
! 54 occidentalis Hook.), Black Locust (Robinia pseudoacacia L.), Osage-orange (Maclura pomifera [Raf.]
Schneid.), redwood, Pacific Yew (Taxus brevifolia Peattie.), Oregon White Oak (Quercus garryana
Douglas ex Hook.), and several species of cedar (Cedrus sp.), fir (Abies sp.), pine (Pinus sp.), and hemlock (Tsuga sp.) (Morrell et al., 1999). A long-term study at Oregon State University compared the durability of untreated posts from these trees and found that Juniper lasted more than 30 years, longer than any of the untreated western species. Western Juniper was selected for the end posts in the WSU Mount Vernon NWREC organic vineyard because of its highly durable nature, natural resistance to decay, availability in the region, and its affordable price when compared to other materials. In addition, it shrinks and swells less than many other PNW species, and has unique bending properties. Before selecting an end post material, compare current costs and availability.
End posts should be set 0.9 m deep or more, and be well braced to resist shifting caused by stresses on the trellis system. The bracing methods and the depth to which posts are set will vary somewhat depending on the soil character and land contour. For example, in the WSU Mount Vernon
NWREC organic vineyard, where the soil type is sandy loam with a slope of 0-2%, end posts are 2.7 m long and sunk into the ground at an angle of 30° from vertical. The brace wire is perpendicular to the ground and held by earth anchors 91 cm long with a 15 cm-helix. By installing the posts and earth anchors at wider angles, less of the wire tension is on the end posts and more is on the anchors. Too much wire tension on an upright end post can pull it inward and wire tension will be lost.
Anchors used to brace the end posts should be of high quality steel with a center or offset eye and helix plate. Angle and depth of setting depends on the method of bracing and on soil type. Install anchors in line with the wire, so the offset eye is just above the ground. Install anchors by hand using a rod, crow bar, or length of pipe. If the ground is very hard, dig a hole to a depth about 1/2 the length of the anchor, then turn the rest of the way by hand. Earth anchor adaptors can be used on post-hole augers for mechanical installation.
Install the end posts before planting but line posts and wires may be installed after planting. Line
! 55 posts, also referred to as intermediate posts, support the wire along the length of the row. Line posts are generally placed every 5.5-7.3 m (3-4 vines). The longer the row, the more spacing is recommended between line posts. Currently there are many different styles of line posts and most are made of metal (Table 2.1). Organic regulations require that these posts are not chemically treated with a galvanizing agent.
Support stakes are needed for each vine during the establishment years, and are placed in the vineyard when vines are planted. Bamboo stakes are often used for the first two years or until vines reach the fruiting wire, after which they can be removed. Steel support stakes have attachment points for easy wire installation, are longer lasting than bamboo stakes but are also more expensive.
For trellis construction, use 9–12 gauge, tempered, high-tensile wire adapted to vineyard uses; it resists rust and stretching better than galvanized wire. Standard vineyard trellis systems include one low irrigation wire (about 38 cm above ground level), one fruiting wire (71 cm above ground level), and two to three pairs of catch wires each spaced 30-60 cm apart above the fruiting wire.
Two commonly used types of wire fasteners are the crimping sleeve and the Gripple®. Inexpensive crimping sleeves are effective for splicing wires, requiring only a crimping tool, and in-row spool type wire tighteners to adjust wire tension. A Gripple splices smooth wire up to six times faster than traditional methods for joining smooth wire. Inside the Gripple, each wire moves in only one direction, passing over high precision gear-tooth rollers. The moment any load is applied in the opposite direction, the rollers bite, locking the wire. Gripples are recommended for in-line splices, loop anchoring and repairs on trellis lines up to 152 m long. A Gripple tensioning tool will be required to pull the wire effectively through the fastener to the required tension.
The trellis system used in the WSU organic research vineyard consists of Western Juniper end posts (Linde Vineyard Supply, Albany, OR) set at a 30° angle with steel “dead man” anchors (Wilson
Irrigation and Orchard Supply, Yakima, WA) and 2.4 m galvanized, steel line posts (R.C. Macdonald
Ltd., Christchurch, New Zealand). The end posts stand 36 in. from the first plant in each row, and the line posts are positioned every 4 plants, or 7.3 m, amounting to 7 posts per row. Cables and gripples
! 56 (Gripple Inc., Aurora, IL 60502) hold the end posts to the anchors. Two 12.5-gauge trellising wires
(Wilson Irrigation and Orchard Supply) are strung at 45 and 60 cm above the ground, along each row, placed in the line post notches, and crimped at the end posts tautly.
Resource Information:
Ahmedullah, M. 1996. Training and trellising grapes for production in Washington. Washington
State University Extention Bulletin EB0637. http://cru.cahe.wsu.edu/CEPublications/
eb0637/eb0637.pdf
Gegner, L. 2002. Organic alternatives to treated lumber. NCAT-Appropriate Technology Transfer in
Rural Areas (ATTRA). http://eagleris ing.net/files/lumber.pdf
Morrell, J.J., D.J. Miller, and P.F. Schneider. 1999. Service life of treated and untreated fence
posts: 1996 post farm report. College of Forestry, Forest Service Research Laboratory.
Oregon State University.
U.S. Dept. Agr. 2000. National organic program final rule. Federal Registry. Vol. 65, No. 246.
Thurs., December 21. p. 41-42. http://www.ams.usda.gov/nop/
nop2000/Final%20Rule/nopfinal.pdf
! 2.3.2 Fertilizer
In vineyards, as in many perennial organic cropping systems, plant nutrition is planned in advance before planting. Organic fertilizers tend to be expensive and so nutrient sources such as compost and manure are commonly used in organic production. Legume cover crops may also be used as a source of biological N. Fertilizer should be purchased at a reliable distributor that is knowledgeable of local product use and organic regulations. Many local farm supply stores now stock organic fertilizers, or products can be sourced online. Before applying any product, first confirm with your certifier that the product is allowable. Allowable materials can change over the course of the year, and there have been several major non-compliance issues with fertilizer products in recent years.
! 57 In vineyards, fertilizer is usually applied only in the row to minimize application rates and costs. The soil test will show current nutrient levels and will provide recommended application rates. Refer to
Dow et al. (1983) for fertilizer recommendations for grapes in Washington. During the first 2-3 years, apply 44-88 kg!N!ha-1 each year in late spring and late fall. From year 4 onwards, apply 66-133 kg!N!ha-1 either in late spring or late fall (Peacock, 2004). Fall applications should only be made if rainfall levels are low and are not conducive to leaching. Typically, grapevines that are deficient in N will have yellowing leaves and do not grow vigorously. Testing the grapevines for nutrient deficiencies can be done by petiole samples during the beginning of the growing season, or leaf samples near the end of the growing season. Although leaf or petiole analyses do not accurately reflect soil N status, most other nutrients are well correlated.
Organic fertilizers can be expensive, and so cover crops are often the main source of nutrients, primarily N, within many organic cropping systems (Altieri, 1995). Legume cover crops naturally fix N from the atmosphere into plant usable form. Mowing the legume cover crop causes the roots to slough off and decompose, releasing N into the soil, where grape roots may absorb it. The mowed cover crop may be left in the alley or placed as mulch into the row where it will decompose on the surface, and N will be flushed into the soil where it will be available for grape plant uptake. Nutrients can also be brought in from outside sources such as manure, compost, or organically allowable fertilizers. Manure and compost are the most common soil amendments used in organic systems
(Watson et al., 2002).
Resource Information:
Bary, A., G. Cogger, and D. Sullivan. 2000. Fertilizing with manure. Washington State University
Extension Publication PNW0533. https://pubs.WSUedu/ItemDetail.aspx?
ProductID=14941&SeriesCode=&CategoryID=173&Keyword=
Davenport, J. and D.A. Horneck. 2011. Sampling guide for nutrient assessment of irrigated
vineyards in the inland Pacific Northwest. Washington State University Extension Bulletin
! 58 PNW622. https://pubs.WSUedu/ItemDetail.aspx?ProductID=15405&SeriesCode=&Cat
egoryID=137&Keyword
Kalita, P. and R. Hermanson. 1999. Animal manure data sheet. Washington State University
Extension Publication EB1719. https://pubs.WSUedu/ItemDetail.aspx?ProductID=13737&
SeriesCode=&CategoryID=173&Keyword
Organic Materials Review Institute (OMRI). 2010. Eugene, Oregon. http://www.omri.org
Schreiner, P., and P. Skinkis. Monitoring grapevine nutrition. eXtension. Oregon State University.
http://www.extension.org/pages/Monitoring_Grapevine_Nutrition
USDA-AMS. 2011. National list of allowed and prohibited substances. United States Department
of Agriculture. Agricultural Marketing Service. http://www.ams.usda.gov/AMSv1.0/getfile?
dDocName=STELPRDC5068682&acct=nopgeninfo
Washington State Department of Agriculture. 2009. Manure and compost guidelines. Organic
Food Program. http://agr.wa.gov/FoodAnimal/Organic/docs/2805_manure_compost_
guide.pdf
Washington State Department of Agriculture. 2011. Brand name material list – sorted by product
name. Organic Food Program. http://agr.wa.gov/FoodAnimal/Organic/docs/bnml_by_
product.pdf
Washington State University. 2011. Analytical laboratories and consultants serving agriculture in
the Pacific Northwest. http://www.puyallup.wsu.edu/analyticallabs/services/
Washington State University. 2011. Grape leaf tissue adequate ranges- nutrient reference table.
http://www.prosser.WSUedu/pdf%20files/nutrient-ref-table.pdf
Washington Wine Industry Foundation, and Vinewise. 2006. Soil management: checklist.
Washington Association of Wine Grape Growers (WAWGG). USDA grant. http://www.vine
wise.org/ files/documents/soil_management.pdf
! 59 2.3.3 Irrigation
Drip and sprinkler irrigation are the two main systems used in vineyards. Today, 80-90% of new vineyards utilize drip irrigation (O’Neal-Coates, 2003). Drip irrigation is most commonly used with grapevines since it uses less water than other systems and it deposits water directly around grapevine roots, thereby increasing irrigation efficacy (Guthman, 2000). In addition, drip irrigation reduces water availability for weed growth between rows, which is of special significance to organic growers who find weed control a primary issue. In contrast, sprinkler irrigation systems increase water availability to weeds growing between the rows and increase foliar moisture, which encourages some diseases. However, sprinkler systems can help when establishing a cover crop in an arid region where precipitation is insufficient.
If irrigation is needed, install the irrigation system prior to planting so newly planted grapevines will have water available to them immediately after transplanting. Install the main line irrigation pipe before installing the end posts. The main-line water pipe is typically buried along one side of the vineyard. Assemble an above ground manifold that includes a filter, pressure reducer, on/off ball valve, and fertilizer injector (Figure 2.2). While a fertilizer injector is not required, it is easier and more economical to inject fertilizer than to apply it manually. Clean filters frequently and replace them as needed to maintain irrigation flow.
Deficit irrigation is the minimization of irrigation during the growing season, especially just before harvest, and is used specifically to control berry size and vegetative growth (Wample and Smithyman,
2002; McCarthy, 2002; O’Neal-Coates, 2003; Chaves et al., 2007). Irrigation can be utilized as a strictly scheduled regime (i.e. twice a week for 2 hours) or can be based on visual cues (i.e. dry soil around grape roots).
In the inland Pacific Northwest, irrigation is essential due to the hot, arid climate. In the maritime
Pacific Northwest, irrigation is needed for newly established vineyards but may not be necessary every year if there is an adequate amount of rainfall throughout the growing season. Established vineyards do not require irrigation if rainfall is sufficient (>610 mm/yr) and temperatures are mild
! 60 enough to limit evapotranspiration (avg. <24 °C), unless the soil has low-water holding capacity.
Refer to the Western Regional Climate Center and Washington State University’s Agricultural
Weather Network for climate information in your area. Studies in western Washington show that irrigated vineyards can be fully productive much sooner than non-irrigated vineyards and could develop more uniformly, suggesting that irrigation costs could prove worthwhile in the long term
(Moulton and King, 2005).
Resource Information:
Hellman, Ed. 2010. Irrigation and water management in a vineyard. eXtension. http://www.exten
sion.org/pages/Irrigation_and_Water_Management
Watson, Jr., J.W. 2005. Drought advisory: grapes. Washington State University Extension and
USDA EM4831E. https://pubs.WSUedu/ItemDetail.aspx?ProductID=14127&SeriesCode=
&CategoryID=137&Keyword=
Washington State University. 2011. Irrigation website. WSU-Prosser. http://irrigation.WSUedu/
Content/Washington-Irrigation.php
Washington State University. 2011. Washington agricultural weather network. http://weather.
WSUedu/
Western Regional Climate Center. 2011. Reno, Nevada. http://www.wrcc.dri.edu/
Washington Wine Industry Foundation, and Vinewise. 2006. Water management: checklist.
Washington Association of Wine Grape Growers (WAWGG). USDA grant.
http://www.vinewise.org/files/documents/water_management.pdf
2.3.4 Planting the grapevines
Be ready to plant the vines as soon as they arrive on site to minimize over-drying that can lead to vine stress and possibly death. Water the new vines intermittently while they wait to be planted and turn on the irrigation in each row as it is planted. Do not irrigate during planting or right before as this
! 61 will cause the soil to become thick, muddy, and difficult to dig.
Plant the grapevines so that all of the roots are underground; typically the planting hole only needs to be about 15 cm deep. If the vines are grafted, the graft union should stay 2.5-5 cm above ground so that the scion does not form roots. If the soil is loose, the plant hole can be dug relatively quickly by hand with a handheld trowel, otherwise a hole-auger may be needed. Remove any paper or plastic container around the plants before planting and do not leave these in the vineyard. If all of the vines cannot be planted in the same day, store the vines in a dark, cool and moist place overnight, making sure they do not dry out.
Resource Information:
Stafne, E. 2011. Planting grape vines. eXtension. http://www.extension.org/pages/
Planting_grape_vines#Planting_Grape_Vines
! 2.3.5 Weed control
Weed control is one of the most demanding and costly tasks in vineyard management and organic farmers do not have many effective and affordable options (Bond and Grundy, 2001; Guthman,
1999). Typical weed control methods include in-row and between-row cultivation (clean cultivation), in-row cultivation and between-row cover crop, or in-row and between-row cover crops. Organic herbicides are available however they are expensive and may not be effective in all situations
(Lanini, 2010). In western Washington, newly planted vineyards are particularly susceptible to weed competition, as weeds are quick to germinate and grow in this cool, moist environment. The establishment years of a vineyard are the most critical in terms of weed management because young vines have difficulty competing for light, water and nutrients with vigorously growing weeds (Elmore and Donaldson, 1999). Consequences of insufficient weed control can be delayed vine growth and maturity, and subsequent delayed income for the grower (Madge, 2005). An efficient weed management program the first two years of establishment usually includes cultivation or mowing in
! 62 alleyways, and cultivation plus hand weeding in the rows (Madge, 2005).
2.3.5.1 In-row
The most important area to keep weed free is the area directly below the vines where most grape root growth and nutrient absorption takes place. This is the area where weed competition can most negatively affect vine growth and it is the area where it is the most difficult to control weeds (Dufour,
2006). Weed control options are limited in newly established organic vineyards, so the best strategy is to reduce weed pressure as much as possible prior to planting. Common strategies include planting several intensive cycles of cover crops, followed by mowing and cultivation. Once the vines are in place, cultivation with specialty devices is possible, but special care must be given to not damage fragile vine roots (Dufour, 2006).
Specialized cultivators are designed to maneuver in narrow spaces and around vines, posts, and irrigation risers and are widely used in vineyards around the world (Madge, 2005). Specialty cultivators have different depth settings that enable the operator to select an appropriate depth to avoid accidental root damage. This allows the operator to cultivate at higher speeds with minimal vine damage, which can be especially beneficial in large vineyards (Madge, 2005). Some cultivators work best running at speeds of around 10 mph, however an inexperienced operator may need to practice at slower speeds beforehand (Sweet and Schreiner, 2010). Specialized cultivators are tractor mounted with a manual or automatic retractable arm that is moved by the operator or triggered by a solid object (Dufour, 2006). The tractor mounting location can differ and includes side, rear, or front-mounted. Other cultivators include rotary hoes and finger weeders that hill soil up under the vines while uprooting weeds and have blades that cut weeds at the ground level, leaving roots underground. A list of specialized cultivators is presented in Table 2.2 along with the main attributes and limitations of each. Select a cultivator that is compatible with your tractor and your budget.
Currently, organic management of vineyard floors typically involves in-row tillage and between-row
! 63 mowing or light cultivation (Hostetler et al., 2007). However, new tools are available that mow under the trellis, cutting vegetation as close as several in. above the soil surface (Wise et al., 2007). These new tools are being used in some commercial vineyards in Washington and elsewhere, and are tractor or ATV mounted with small side decks that pivot around vine trunks (Wise et al., 2007).
Cultivators cannot reach all vegetation, thus occasional hand weeding is necessary to maintain clean in-row areas, especially around the vines and posts. Other options for in-row weed control include organically approved contact herbicides, propane fueled weed burners, and mulch. These require additional costs and are usually not completely effective. Cover crops have been used for in- row weed control; however, they are only used in vineyards with too much vine vigor where their competition with the grapevines can be beneficial.
2.3.5.2 Between-row
In organic vineyards, between-row areas (alleyways) are usually planted with a perennial companion grass mix that is mowed 1-4 times each year to control weeds (Tesic et al., 2007; Sweet and Schreiner, 2010). Mow highly vigorous cover crops more often than low vigor cover crops.
Mowing height should be below the plants’ regeneration point. For example, mowing at 20-25 cm can control medium to tall broadleaf weeds while allowing legumes to regenerate. On the other hand, mowing at 2.5-5 cm can control a larger number of species and tends to favor grasses as they have a physiologically lower regeneration point (Madge, 2005). The cuttings can be left in the alleyway or thrown into the vine row and used as mulch and a nutrient source (McGourty, 2004). To increase competition, reduce vine vigor, and reduce soil compaction or disturbance, mow every other row only (Pardini et al., 2002).
Alleyways can be clean cultivated using discs or rototillers without damaging grapevine roots
(Madge, 2005). To maintain low vegetation levels, cultivation is sometimes needed several times during the growing season, thereby increasing costs, erosion potential, soil compaction, and vine root damage potential (Pool et al., 1993). Clean cultivation is most commonly used in dry-land
! 64 conditions to minimize competition for water between the grapevines and the alleyway vegetation as this has been shown to dramatically decrease yields (Van Huyssteen and Weber, 1980).
2.3.5.3 Cover crops
Cover crops are widely used in both organic and conventional vineyards worldwide as they provide numerous benefits such as: increase soil organic matter, add N to the soil (i.e. legumes), reduce nutrient leaching, encourage micro-flora and earthworms, reduce soil erosion potential, increase soil porosity, reduce soil compaction, reduce surface crusting, and improve machinery movement
(Pardini et al., 2002). There are many options for cover crop species and each provides different benefits and limitations, depending on the amounts and types of weeds to be managed. Many factors can affect cover crop efficacy and competition for water and nutrients with the vine including climate, soil quality and texture, topography, vine planting density, rootstock and scion cultivars, training system, and trellis structure (Pardini et al., 2002). Choose a cover crop species and management regime based on your specific vineyard needs.
Cover crops are most often planted only in the alleyways, and the area directly under vines is kept clean. Vine vigor is directly affected by in-row vegetation, especially in young vineyards. If reduced vine vigor is desired, in-row cover crops may be used. Although much of western Washington has high precipitation levels, high-density cover crops in the alleyways can create significant competition for water. In areas where water is limiting, use drought tolerant covers crops (Olmstead et al., 2001).
Cultivate the alleyways before seeding the cover crop to reduce weed populations and improve the seedbed. Seeding depth should coordinate with seed size and seedling size and vigor. Grass seeds should be seeded at a shallow depth, whereas bigger seeds, like field pea, should be seeded deeper.
Any litter on the soil surface should be removed and the soil surface should be level to have uniform seeding depth (Porter, 1998). For more information on cover crop species and their uses, refer to the cover crop resource information below.
! 65 Resource Information:
Clark, A. 2007. Managing cover crops profitably. Sustainable Agriculture Research and Education
(SARE). http://www.sare.org/publications/covercrops/index.shtml
Olmstead, M. 2006. Cover crops as a floor management strategy for Pacific Northwest vineyards.
Washington State University Extension Bulletin EB2010. http://
cru.cahe.WSUedu/CEPublications/eb2010/eb2010.pdf
Washington State University, Grant-Adams. 2011. Cover crops for the Columbia Basin.
http://grant-adams.WSUedu/agriculture/covercrops/columbia_basin_covercrops.htm
! 2.3.6 Disease and insect pest control
Several organisms such as bacteria, fungi, viruses, and nematodes cause grapevine diseases.
Many of these diseases cause only minor problems in vineyards, however a few such as crown gall and powdery mildew can lead to severe vine damage or death and can infest an entire vineyard in a relatively short period of time. The best way to protect grapevines from diseases is through preventative efforts. This includes scouting for symptoms (e.g., leaf discoloration, fungal growth, leaf venation changes, etc.), testing grapevine tissue regularly, and minimizing practices that promote disease infection (i.e. over-watering or insufficient alleyway and canopy management). The
Washington agricultural weather network (www.agweathernet.wsu.edu) is a WSU online database of weather conditions and the associated risks for disease outbreak. Models for grape powdery mildew and bunch rot, two very economically important diseases for Washington State, are available through this system for eastern Washington. Models also exist for western Oregon, but research is just beginning in western Washington.
There are many insects that can have detrimental effects on grapevines, like mites (e.g., black rust and spider mites), worms (e.g., cutworms), flies (Spotted Wing Drosophila), and other insects (e.g., leafhoppers and mealybugs). Recently, the Spotted Wing Drosophila (SWD) (Drosophila suzukii) has
! 66 invaded the Pacific Northwest. SWD deposit eggs into ripening grapes (as well as other types of fruit) while they are still on the vine, and may cause significant losses in fruit prior to harvest. Monitor the vineyard for potential pests and diseases and take appropriate management steps before infestation occurs.
Resource Information:
Ahmedullah, M., and D. Johnson. 1986. Botrytis Bunch Rot of grape. Washington State University
Extension Bulletin EB1370. https://cru84.cahe.WSUedu/ItemDetail.aspx?
ProductID=13564&SeriesCode=&CategoryID=&Keyword=EB1370
Food and Environmental Quality Lab. 2011. Leaf symptoms of 2,4-D damage. Washington State
University, Tri-cities, Richland, WA. http://feql.WSUedu/eb/index.htm
Grove, G.G., J. Lunden, and S. Spayd. 2005. Use of spray oils in Washington powdery mildew
management programs. Washington State University Department of Plant Pathology New
Series #0382. Plant Management Network (PMN). http://www.
plantmanagementnetwork.org/pub/php/research/2005/oils/
Integrated Pest Management Centers. 2004. Pest management strategic plan for grapes in
Washington State: summary of workshop. March 17, 2004, Pasco, WA. http://www.
ipmcenters.org/pmsp/pdf/WAWineGrapePMSP.pdf
Olmstead, M.A., J. Davenport, and R. Smithyman. 2005. Blackleaf in grapes. Washington State
University Extension Bulletin EB0745. https://pubs.WSUedu/ItemDetail.aspx?
ProductID=13355
Olsen, K., and W. Cone. 1997. Grape leafhoppers in Washington. Washington State University
Extension Bulletin EB1828. http://cru.cahe.WSUedu/CEPublications/
eb1828/eb1828.html
Pscheidt, J. 2010. Eutypa Dieback disease. Oregon State University - online guide to plant disease
control. http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=519
! 67 Washington State University. 2011. Biology and control of major Pacific Northwest grape pests.
WSU Department of Viticulture and Enology, Tri-Cities. http://www2.tri
city.WSUedu/aenews/Grape/EB1871Biologyandcontrol.html
Washington State University. 2011. Grapevine virology website. WSU Viticulture and Enology
Department, Virology. http://wine.WSUedu/research/virology/
Washington State University Agricultural Integrated Pest Management. 2011. Spotted Wing
Drosophila website. WSU Extension, Prosser. http://extension.WSUedu/
swd/Pages/default.aspx
Washington State University Extension. 2011. Pest management guide for grapes in Washington.
WSU Extension Bulletin EB0762. http://cru.cahe.WSUedu/
CEPublications/eb0762/eb0762.pdf
Washington Wine Industry Foundation and Vinewise. 2006. Pest management: checklist.
Washington Association of Wine Grape Growers (WAWGG). USDA grant. http://
www.vinewise.org/files/documents/Pest_Management_FINAL.pdf
Watson, J., W. Cone, and M. Hasket. 1990. Grape phylloxera in Washington. Washington State
University Extension Bulletin EB1566. http://cru.cahe.WSUedu/CEPublications
/eb1566/eb1566.html
University of California Statewide Integrated Pest Management Program Online. 2002. Grape
cutworms. UC, Davis. http://www.ipm.ucdavis.edu/PMG/r302300511.html
University of California Statewide Integrated Pest Management Program Online. 2001. Grape
scales. UC, Davis. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/ pn7408.html
University of California Statewide Integrated Pest Management Program Online. 2002. Grape
thrips. UC, Davis. http://www.ipm.ucdavis.edu/PMG/r302300911.html
! 2.3.7 Pruning and training
Grapevines are pruned every year during the dormant season (December – March). After the first
! 68 growing season, prune the vines back to two buds. After the second growing season, prune the vines back to the fruiting wire with two buds at or above the wire. After the third growing season, or the fourth if the vines did not grow vigorously, prune the vines back to a standard form that will be maintained for following years. Not much pruning will be needed during the growing season until the grapevines are mature enough to produce harvestable grapes, which is typically after the fourth year.
How much, and in what form, the vines are pruned will be based on the grower’s preference. For organic grape production, pruning is used to maintain good air circulation to prevent diseases such as grape powdery mildew (Erysiphe necator) and Botrytis Bunch Rot (Botrytis cinera). The best control method for Botrytis Bunch Rot, which develops in grape clusters where there is insufficient air circulation, is to remove leaves surrounding the cluster, exposing it to drying conditions (Gubler et al., 1987; English et al., 1988). Refer to resource information for detailed information regarding pruning.
The training system should exploit the site’s limiting factors (i.e. light, water, wind) as much as possible. In general, the vertical shoot positioning (VSP) training system, where the vine shoots are positioned upright, maximizes canopy light penetration and air circulation and is recommended for western Washington (Olmstead et al., 2006). In eastern Washington solar radiation levels are high and a training system that enables more leaf area and less light exposure, like Geneva Double
Curtain (GDC), can be used. Very fertile soils and high water availability, such as found in western
Washington, can cause vines to grow too vigorously, resulting in undesirable fruit composition or fruit exposure. In these circumstances a training system such as the Scott-Henry that minimizes vine vigor may be the best choice (Henry, 1991; Olmstead et al., 2006; Reynolds and Vanden Heuvel,
2009). A general guideline for maximizing light exposure is a 1:1 ratio of trellis height to row width
(Smart et al., 1982).
During the first year, grapevines will not need much training until their growth reaches the fruiting wire. Once the young vines can be tied to the wire, train the vines based on lighting needs, growth potential and future harvesting methods. For example, increasing the canopy’s surface area will
! 69 increase sunlight interception; or, decreasing the canopy’s surface area of a vineyard planted on a steep slope that is subjected to high velocity winds will minimize wind damage. In some climates, nutrients, water, or light are not limiting to high-quality grape production, and shoot pruning or leaf thinning may be needed to balance vine growth with the available resources.
Resource Information:
Ferguson, H. 2006. Canopy management for Pacific Northwest vineyards. Washington State
University Extension Bulletin EB2018E. https://pubs.WSUedu/ItemDetail.as
px?ProductID=13975&SeriesCode=&CategoryID=137&Keyword
! 2.4 Conclusions
Grapes can be successfully grown and managed organically throughout the Pacific Northwest.
Although organic methods are more time-consuming and costly, and may require more planning to be effective, the returns per ton can be greater than for conventionally produced grapes. Review the organic certification regulations and discuss with an expert any questions you may have prior to vineyard establishment. A primary difference between organic and conventional vineyards is end posts. Organic vineyards may not contain end posts treated with prohibited substances. Treated end posts would need to be replaced and three years of transition time would be required before the vineyard could be organically certified.
Choose a vineyard site that offers as many climatic advantages as possible given your regional climate. Select a cultivar that is well suited to the climate of your vineyards as this will minimize management issues and optimize production success. If necessary, prior to planting grapes, spend
1-2 years cover cropping, mowing and tilling the vineyard site and spot treating perennial weeds as needed to control weeds. Weed management is often the most challenging task in an organic vineyard and it is easier and less expensive to intensively manage weeds before the vineyard is established. Use the establishment phase of your vineyard to learn its advantages and limitations so
! 70 that when the vines are ready to produce grapes, you will have a management regime that best suits your vineyard.
! 71 ! ! 2.5 References
Altieri, M.A. 1995. Agroecology: the science of sustainable agriculture. Westview Press. Boulder,
CO.
Bond, W. and A.C. Grundy. 2001. Non-chemical weed management in organic farming systems.
Weed Res. 41:383–405.
Chaves, M.M., T.P. Santos, C.R. Souza, M.F. Ortuño, M.L. Rodrigues, C.M. Lopes, J.P. Maroco, and
J.S. Pereira. 2007. Deficit irrigation in grapevine improves water-use efficiency while
controlling vigour and production quality. Ann. Appl. Biol. 150:237–252.
Dow, A.I., W.J. Clore, A.R. Halvorson, and R.B. Tukey. 1983. Fertilizer guide: irrigated vineyards.
Wash. St. Univ. Ext. Pub. FG-13.
Dry, P.R. 2000. Canopy management for fruitfulness. Aust. J. Grape Wine Res. 6:109-115.
Dufour, R. 2006. Grapes: organic production. APPROPRIATE TECH. TRANSFER RURAL AREAS
(ATTRA). NAT. CTR. APPROPRIATE TECH. (NCAT). U.S. Dept. Agr. Rur. Bus. Coop. Serv..
Elmore, C., and D. Donaldson. 1999. UC pest management guidelines: grape integrated weed
management.
English, J.T., A.M. Bledsoe, and J. Marois. 1990. Influence of leaf removal from the fruit cluster
zone on the components of evaporative potential within grapevine canopies. Agr. Ecos.
Environ. 31:49–61.
Flexas, J., J. Galmés, A. Gallé, J. Gulías, A. Pou, M. Ribas-Carbo, M. Tomàs, and H. Medrano. 2010.
Improving water use efficiency in grapevines: potential physiological targets for
biotechnological improvement. Aust. J. Grape & Wine Res. 16:106–121.
Galet, P. 1998. Grape varieties and rootstock varieties. Château de Chaintré, Chaintré, France.
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! 75 Sacramento, CA. Feb. 6-7.
! 76
2.6 Tables
Table 2.1 Line post options and features for organic vineyard establishment.
Type/Name Pros Features
Mannwerks® post • Gentle on harvesting Cold-formed hot rolled steel with equipment min. tensile strength – 65,000 psi and min. yield point – 50,000 psi • Stable in soil • User friendly
Rib back post • Ideal for rocky or hard pan 9 feet long (3 lbs of steel per foot) soils with 3/8-inch diameter wire holes run entire length of post every 2 • Could be used as end post inches
Diamond back post • Could be used as end post Diamond shape and rounded because diamond shape edges provides adequate strength • Easy on mechanical harvesters
Fencing T-post • Inexpensive Requires installation of wire clips to support the wire (additional • Available in various lengths expense and labor)
Rolled Edge Vertical • Side notches make wire 8 feet long, 13 gauge (or 12 line postz placement easy gauge for extra strength) and self- colored for natural ‘wood’ look • Do not require wire clips without wood preservatives • Suitable for mechanical harvests zUsed as in-row support posts in the WSU Mount Vernon NWREC organic vineyard.
! 77 Table 2.2 Specialized cultivators commonly used in vineyards (Dufour, 2006).
Type/Name Pros/Cons Features
French plow or grape Pros: heavy duty, traditionally used • Does best in moist soils hoe Cons: soil is thrown back under the vine after the pass
Weed Badger (Weed Pros: heavy duty, many available • Lots of moving parts Badger Division, models, fits with cultivator or mower, • Varies in durability by Marion, ND) works for any size weed, adjustable model head for different angles and slopes
Cons: very wide and slow
Wonder Weeder Pros: fast, allows for closer cultivation • Has an articulating swing- (Harris to the vine than other cultivators arm with rotary harrow Manufacturing, and disk attachments Cons: very expensive Burbank, WA) • Touch sensitive ‘shear bar’ !
! 78
2.7 Figures
Fig. 2.1 American viticultural areas in Washington State (Courtesy of the Washington Wine
Commission, 2010).
! 79 !!! Direction of water flow during:
Fertigation/fertilization -or- Normal irrigation
Fig. 2.2 Irrigation manifold used at the WSU Mount Vernon NWREC organic vineyard showing
components and direction of water flow.
! 80 CHAPTER 3. WEED CONTROL IN A NEWLY ESTABLISHED ORGANIC VINEYARD
3.1 Abstract
Environmental concerns regarding the impact of agriculture have created ever-growing pressure for growers to incorporate increasingly sustainable practices. Consumer demand for organic grape products, the major organic horticultural fruit crop worldwide, has led to growers seeking more information on organic grape production. Within organic grape production, weed management is the most critical issue with a newly established vineyard. In 2009, an organic vineyard was established to analyze the effectiveness of cover crops compared to tillage for weed control. Five treatments were applied to ‘Pinot noir précoce’ (PNP) and ‘Madeleine angevine’ (MA) grapes during the first two years of establishment. Weed control treatments were standard cultivation between-row and hand- weeding in-row (ST), in-row tillage with Wonder Weeder® and grass ((Lolium perenne L. and Festuca rubra L. ssp. arenaria ‘Osbeck’ F. Aresch.) cover crop seeded between-row (WW), winter wheat
(Triticum aestivum L. cv. ‘Otis’) cover crop and in-row string-trimming (W), Austrian winter pea (Pisum arvense L.) cover crop and in-row string-trimming (P), and wheat and pea cover crop mix and in-row string-trimming (W/P). Weed biomass in September 2009 was greater in the P treatment than under
ST and W. Weed biomass in July 2010 was greater in W, P, and W/P than in ST or WW. By
September, however, weed biomass was not different among treatments. Plot maintenance in ST, for the two growing seasons combined, required more time than WW or the annual cover crop treatments. MA produced more shoot growth than PNP in September 2010. Grapevines under ST measured significantly longer than vines under any other treatment. Weed biomass was reduced by the wheat and pea cover crops, and the vine growth was also negatively affected by these cover crops. Wheat and pea did not differ in their level of competition with the weeds or the grapevines.
Cultivation and hand weeding reduced weed biomass, but hand weeding required the greatest maintenance. In a newly established organic vineyard, the most effective and efficient management regime includes a vegetative-free zone around the vines (i.e. in-row) maintained using a specialty
! 81 cultivator (e.g., Wonder Weeder), to minimize the need for hand weeding and a perennial cover crop in the alleyway to reduce weed biomass.
3.2 Introduction
In the last seventeen years, the Pacific Northwest (PNW), which includes Washington, Oregon, and
Idaho, has developed into a wine grape (Vitis vinifera L.) growing region second only in U.S. production to California (O’Neal-Coates, 2003). Within the PNW, Washington State accounts for almost 90% of the wine grape production and as of 2010, 13,800 of Washington’s 24,280 grape hectares were wine grapes (USDA-NASS, 2010). Environmental concerns regarding increased soil erosion, decreased soil fertility, limited water supply, biodiversity loss, and herbicide resistance are leading to increased efforts to maintain sustainable agricultural systems (Krauss et al., 2010; Lal et al., 2007; Montgomery, 2007; Triplett and Dick, 2008). Many organic farmers rely on mechanical and hand cultivation for weed control; but while these methods are highly effective they are also labor-intensive and not sustainable (Guthman, 2000). Weed management practices that promote sustainability include the use of cover crops, mulches, reduced or no-tillage, and organic herbicides
(Altieri, 1995). These practices have allowed grapes to be successfully managed organically and produce qualities comparable to conventionally managed grapes (White, 1996). Weed management is the most expensive and the most technically challenging practice for organic grape production
(Dufour, 2006; Guthman, 2000).
It is common to use cover crops in the alleyways and cultivation under the vines for weed control in organic vineyards. Specialty cultivators that can work close to the vines without damage are essential. Currently, many in-row cultivators specifically designed for orchard and vineyard use are available (e.g., Wonder Weeder [Harris Manufacturing, Burbank, WA], Weed Badger [Weed Badger
Division, Marion, ND] and French plow). These devices are able to cultivate much closer to the vine row than standard cultivators; however the area immediately around the vines still requires manual weeding (Zabadal, 1999).
! 82 Cover cropping is an alternative weed suppression technique used in organic and conventional vineyards worldwide (Dastgheib and Frampton, 2000; Liebman and Davis, 2000; Pardini et al.,
2002). Recent studies have demonstrated that cover crops can increase soil organic matter, micro- flora and earthworm populations (Tan and Crabtree, 1990; Davies et al., 2001; Nevens and Reheul,
2002). Cover crops can also decrease the need for fertilizers through inherent nutrient additions (i.e. legumes fixing nitrogen). Additionally, cover crops can reduce pH, nitrate leaching (Hansen and
Djurhuus, 1997), soil erosion, soil compaction, surface crusting, and improve soil porosity and machinery movement (Gulick et al., 1994; Hogue and Neilsen, 1987; Langdale et al., 1991; Lu et al.,
2000; Pardini et al., 2002; Rinnofner et al., 2008). Climate, soil quality and texture, topography, vine planting density, rootstock and scion cultivar, training system, and trellis structure all contribute to the efficacy of a cover crop and interact to make a cover crop choice particularly difficult (Pardini et al., 2002). Cover crops are most often planted in alleyways and not within the vine row, unless reduced vine vigor is desired in an established vineyard (Celette et al., 2005; Celette et al., 2009;
Tesic et al., 2007). Most commercial wine grape growers are changing to drip irrigation for better deficit irrigation execution, and drought tolerant cover crop species (e.g., forage legumes, grasses, and some forbs) are used (Clark, 2007; Olmstead et al., 2001).
Legumes form a symbiotic relationship with bacteria that have nitrogen-fixing attributes. As a result, legume cover crops can be planted to reduce fertilizer costs. Mowing and tillage of the legumes during bloom are required for rapid and optimum nitrogen mineralization (Doran and Smith,
1991, McGourty, 2004). Without cover crop incorporation, the decomposition rate is slowed and nitrogen mineralization is delayed (Ingels et al., 1994). Grasses have large, expansive root systems that reduce soil erosion, increase soil organic matter from residual biomass, improve soil porosity, increase water penetration and drainage, and reduce vine vigor (Blake, 1991; Bugg et al., 1996;
Morlat and Jacquet, 2003; McGourty, 2004). Unlike legumes, grasses have high C:N ratios, causing
N to be tied up in the soil (Mary et al., 1996; Coppens et al., 2006; Celette et al., 2009), however, nitrate leaching is reduced (Morgan et al., 1942; Karraker, 1950; McKell et al., 1969; Martinez and
! 83 Guiraud, 1990; Meisinger et a., 1991; Ingels et al., 1994; Brandi-Dohrn et al., 1997; Sattell et al.,
1999). Mowing a grass cover crop increases organic matter, releases nitrogen and potassium into the soil, and increases pH, particularly if the residue is incorporated into the soil (Snapp and Borden,
2005; Ripoche et al, 2011). Remaining stubble of a grass cover crop also allows for greater solar radiation absorption by the soil, reduces dust, and provides traction for equipment (Gaffney and Van
Der Grinten, 1991; Bugg et al., 1996; Olmstead, 2006).
In western Washington, wheat (Triticum aestivum L.) and annual ryegrass (Lolium multiflorum L.) are frequently utilized as cover crops in vineyards. In western Oregon, where climate and soil properties are similar to western Washington, mixtures of winter annuals, clovers, native grasses, native meadow species, perennial grass and clover, and resident vegetation demonstrated low competition with mature grapevines (Sweet and Schreiner, 2010). Each had minimal impact on the vine’s growth compared to clean cultivation, showing it is possible to establish a high vigor cover crop without negatively affecting grapevine growth. Young vines can be more susceptible to cover crop competition since they have not developed nutrient reserves, therefore, cover crops for new vineyards should be less vigorous than those for established vineyards (Eastham et al., 1996). It is not well known whether less competitive cover crops provide adequate weed suppression in a newly established vineyard without impacting vine growth. Thus, the objective of this study was to investigate the efficacy of four cover crop and tillage regimes for weed suppression in a newly planted vineyard in transition to organic production.
3.3 Materials and methods
3.3.1 Vineyard establishment
In 2008, a 1.2-ha (3-acre) field was identified to establish an organic research vineyard at the
Washington State University Northwestern Washington Research and Extension Center (NWREC)
(Mount Vernon, WA). The soil type was a Skagit Series soil (fine-silty, mixed, super-active, nonacid, and mesic Fluvaquentic Endoaquepts). Field records indicated the last non-organic chemical
! 84 application was September 2007; therefore, organic certification was possible in October 2010.
Untreated barley (Hordeum vulgare L) was purchased from the local farm supply store (Skagit
Farmer’s Supply, Mt. Vernon, WA) and planted on August 13, 2008 as a cover crop to provide weed control and potentially add organic matter to the soil. Barley grain was harvested (September 29,
2008) and the field was rototilled, disked, and plowed to provide a proper planting bed for both grapevines and weed suppression treatments. A winter cover crop (untreated cereal rye [Secale cereale L.]) was purchased from the local farm supply store (Skagit Farmer’s Supply) and planted in
October 2008. This rye cover crop was incorporated into the field on March 26, 2009. Soil samples were collected from the field site in October 2008 were analyzed (Soiltest Farm Consultants, Inc.,
Moses Lake, WA) and interpreted (Marx et al., 1996; Moulton and King, 2005) (Table 3.1), and organic amendments were incorporated accordingly (see Soil Preparations below).
The vineyard established for this study was 180.4 m (592 ft) wide and 48.2 m (158 ft) long, equaling 0.87 ha (2.14 A). Spacing for equipment turnaround was approximately 4.9 m (16 ft) wide surrounding the vineyard, totaling 1.23 ha (3.03 A). The experiment was a split-plot, randomized complete block design (RCBD) with 3 replications. The main plot is weed suppression treatment and the sub-plot is grape cultivar. Each main plot consists of 9 rows, each 25.6 m (84 ft) long with 14 plants per row (2.4 m between rows and 1.8 m between vines).
The subplots included two wine grape cultivars, ‘Madeleine angevine’ (MA; 4 rows) and ‘Pinot noir précoce’ (PNP; 5 rows). In western Washington, the expected yield for PNP is 1.5 kg (3.2 lbs) per vine and for MA it is 3.6 kg (8 lbs) per vine. Based on these average yields, the number of data vines differed for MA (N=20) and PNP (N=30). An additional two plants at the end of each data row were considered buffer plants. Vineyard rows were oriented in a north-south direction to optimize sunlight interception for this location. All vines were pruned back to 2 nodes on February 16 and 18, 2010 and trained to a spur-pruned, bilateral cordon system. The vineyard trellis was established per standard protocols using organically approved materials (OMRI, 2009).
! 85
3.3.2 Climate
Climatic characteristics of the maritime region in northwestern Washington include cool, dry summers and mild, wet winters. Precipitation ranges from 310-1270 mm (12 to 50 in.) per year or higher and mostly occurs as rainfall during late fall and early spring. The heat units of this area can vary from 1400 to 2300 growing degree-days (GDD; base 10 °C, or 50 °F). This amount of heat is low compared to the Columbia Basin, east of the Cascades where GDD ranges from 2000 to 3500
GDD. The Puget Sound American Viticultural Area (AVA) has a long-term average of 1656 GDD and the Red Mountain AVA, representing the hottest area in eastern WA, has a long-term average of
3302 (>10 °C) GDD (Washington State University, 2011). These low average GDDs for the Puget
Sound AVA indicate that grape varieties best suited for this area are early ripening cultivars like
Siegerrebe, MA, Muller-Thurgau, and PNP (Moulton and King, 2005).
3.3.3 Grapevines
Two grapevine cultivars were chosen based on vineyard site meso-climate and local wine cultivar trends. Madeleine angevine is a French, white wine variety that has been grown in western
Washington for 25 years (Moulton and King, 2005). It is known to be productive but susceptible to water stress and fruit rot. Pinot noir précoce is a French, red wine variety similar to Pinot noir with the exception that its ripening period is accelerated by two weeks (Moulton and King, 2005), a positive aspect for the region.
Couderc 3309 is a popular rootstock for California and the maritime Pacific Northwest, including western Washington. Couderc 3309 induces low to moderate vigor in scions and is adapted to deep soils (Christensen, 2003). Previous research conducted at WSU-NWREC indicated Pinot noir scions grafted to Couderc 3309 rootstock yielded juice with higher °Brix, lower titratable acid, and higher pH than self-rooted vines. Couderc 3309 rootstocks allowed Pinot noir vines to mature faster and ripen more quickly than self-rooted vines over the same period of time (Moulton and King, 2005).
! 86 In October 2008, 1180 PNP and 890 MA scions were grafted to Couderc 3309 rootstocks and hardened at Cloud Mountain Nursery (Everson, WA). Grapevines were transported and transplanted
(June 1-2, 2008). Due to the unusually cold temperatures in the 2008-09-winter season, about 17% of MA vines suffered winter injury. Due to this plant shortage, 10 border rows (140 vines total) were not planted until June 2010, when replacement vines were acquired.
3.3.3.1 Irrigation
On May 18, 2009, installation of the irrigation system began with digging a trench 45–61 cm (18-
24 in.) deep on the North side of the vineyard, from East to West. A 5.1-cm (2-in.) mainline PVC pipe was installed in the trench along the North end of the vineyard. At 2.4-m (8-ft) intervals, 74-5.1 cm x
5.1 cm x 1.9 cm (3/4 in.) “Tees” were fitted to the mainline, and drip tape fittings (Larson Irrigation,
San Diego, CA) were attached to risers just above ground level. A 2-in. ball valve (Larson Irrigation) was installed between the main water source and the manifold and at each end of the mainline. The manifold was installed to connect the main water source to the mainline, and included a pressure reducer (Larson Irrigation) followed by a Mazzei injector (Mazzei Injector Company, Bakersfield, CA) isolated by ball valves (Larson Irrigation), and a 200-mesh filter (Larson Irrigation). Once the irrigation system was completely assembled, it was flushed and the trench was filled in and compacted using a loading skid-steer to move the soil and a tamper.
After the irrigation system was flushed, drip tape (Point Source Irrigation, Fresno, CA) was laid out along each row and connected to the water source using drip tape adapters. The drip tape diameter was 18 mm and allowed 2.1 L (0.55 gal) per hour for every 0.6 m (24 in.). The drip emitters were every 0.6 m (2 ft) therefore each plant was within 0.3 m (1 ft) of an irrigation emitter.
3.3.3.2 Fertilizer
Fertilizers and soil amendments approved for use in certified organic production systems were used to adjust soil fertility conditions (WSDA-OFP, Olympia, WA; OMRI, Eugene OR). These included bone meal (5N-16P-0K), K-Mag (0N-0P-22K-1Mg) and granulated gypsum (22% Ca). The vineyard
! 87 was rototilled 18 May, 2009, and soil amendments were applied 19 and 22 May, 2009. Bone-meal
(Wilbur-Ellis Co., Yakima, WA) was applied at 207 kg!ha-1 (185 lbs!A-1) or 2.6 kg!row-1 (5.7 lbs!row-1) using a push fertilizer/drop spreader (Scott’s Miracle Grow Company, Marysville, OH) and pelletized gypsum (Pacific Calcium Inc. Tonasket, WA) was applied at 1233 kg!ha-1 (1100 lbs!A-1) or 15 kg!row-1
(33 lbs!row-1), using a 1.2-m (4-ft) wide drop spreader (Gandy Company, Owatonna, MN) ATV attachment; both were incorporated into the soil to a depth of 15-21 cm (6-8 in.) by tillage. K-Mag
(The Mosaic Co., Plymouth, MN) was applied at 646 kg!ha-1 (577 lbs!A-1) or 7.8 kg!row-1 (17.3 lbs!row-
1), using a Nordsten seed planter (Kongskilde Industries A/S, Denmark).
3.3.3.3 Cover crop treatments
The study included five main plot weed suppression treatments:
1. between-row tillage, in-row hand weeding (ST);
2. between-row companion cover crop mix of 75% Dwarf Perennial Ryegrass (Lolium perenne
L.) Gator III and 25% Creeping Red Fescue (Festuca rubra L. ssp. arenaria ‘Osbeck’ F.
Aresch.) and mowing, in-row tillage with the Wonder Weeder (WW);
3. between-row hard white winter wheat (Triticum aestivum L. cv. ‘Otis’) cover crop seeded at
334 kg!ha-1 (300 lbs!A-1) and mowing, in-row string-trimming (W);
4. between-row Austrian winter pea (Pisum arvense L.) (cultivar not identified by the supplier)
cover crop seeded at 334 kg!ha-1 (300 lbs!A-1) and mowing, in-row string-trimming (P);
5. between-row winter wheat and winter pea mix seeded at 2:1 ratio, respectively, and
mowing, in-row string-trimming (W/P).
Organic winter wheat and a generic organic winter pea were planted in 2009 and 2010. In 2009, cover crop seed was purchased from Peaceful Valley Farm & Garden Supply (Grass Valley, CA) and in
2010 cover crop seed was purchased from Pacific Northwest Farmers Cooperative (Genesee, ID).
In both years, W and P treatments were seeded at 335 kg!ha-1 and the winter wheat plus winter pea cover crop treatment was seeded in a 2:1 ratio of wheat to winter pea at 224:112 kg!ha-1
! 88 (200:100 lbs!A-1). Cover crops were planted in W, P, and W/P plots using an Ortho® Whirly-bird
Spreader (Marysville, OH) on 30 June 2009 and on 23 March 2010 (Table 3.2). Preferred seed placement was in the alleys between each row, leaving vine rows (i.e. in-row areas) clear, however
100% coverage was not possible using a broadcast seeder. A chain-link fence segment was attached to an ATV and dragged down the row centers to incorporate the seeds 2.5-5 cm (1-2 in.) into the soil; afterwards, the soil was pressed using a roller attachment. In 2009, the companion mix was seeded using the Whirly-bird broadcast spreader at 11 kg!ha-1 (10 lbs!A-1), but due to insufficient coverage, the companion grass mix was seeded at 15 kg!ha-1 (13 lbs!A-1) in 2010, resulting in better coverage.
3.3.4 Vineyard maintenance
The vineyard was irrigated twice per week for an average of 3 hours (1 June through 1 September in 2009, and from 6 July until 1 September in 2010). In both years, the irrigation rate was 2.1 L!h-1
(0.55 gal.!h-1) per 0.6 m (2 ft) of row, or each drip emitter. In 2009, the vineyard was fertigated with
17.8 L!h-1 (4.7 gal.!h-1) of Vegan Nitrogen (6N-0P-0K) (Westbridge Agricultural Products, Vista, CA) on three occasions (30 June, 7 July, and 21 July). In 2010 the vineyard was fertigated with 20.4 L!h-1
(5.4 gal.!h-1) of Phytamin fish fertilizer (4N-2P-4K) (California Organic Fertilizers Inc., Fresno, CA), because Vegan Nitrogen was no longer listed as an accepted material in organic systems, on July 27 and August 3. The total N fertilizer applied was 123 kg!ha-1 (110 lbs!A-1) in 2009 and 247 kg!ha-1
(220 lbs!A-1) in 2010.
On October 8, 2009, the headlands were seeded with the same non-treated grass mix used in WW plots described earlier. The headlands were mowed when vegetation height hindered traffic in the vineyard, on May 11, May 27, June 19, and July 6 in 2010.
3.3.5 Measurements
Measurements taken in the vineyard include: shoot length, shoot diameter or caliper, weed biomass, and time requirements for maintenance.
! 89 3.3.5.1 Shoot length
Shoot length was measured on five randomly selected vines from previously designated data vines.
Effort was made to use the same five vines for measurements throughout the entire 2-year study by tagging the vines. However due to unintended vine death from string trimming and/or poor initial vine health, not all measurements were done on the same vines over the course of this study. Vines directly adjacent to the dead or damaged vine were preferred when choosing the replacement.
One-year old shoot growth was measured from base of the shoot to the tip in both years. In 2009, shoot length was measured on July 30, August 14, and September 26, while in 2010, shoot length was measured on May 27, June 10, June 24, July 8, July 22, August 5, and August 19. On August 24,
2010, the non-measurement vines were pruned back to the fruiting wire to induce lateral shoot production, however some measurement vines were mistakenly pruned which prevented further shoot length measurements.
3.3.5.2 Shoot diameter
Shoot diameter (caliper) was not measured during year 1 because vine growth did not appear significantly different across treatments. In year 2, shoot diameter was measured at 15 cm (6 in.) above the graft union on June 8 and September 10. Shoot diameter was measured using a Storm® digital caliper measurer (Central Tools Inc., Cranston, RI).
3.3.5.3 Weed biomass
Weed measurements both years included two weed biomass collections, on 3 August and 27
September in 2009 and on 22 July and 27 September 2010. Weed biomass collections were made in each subplot in the between-row and in-row areas using a 0.13 m2 quadrat placed randomly on the ground. At each measurement time, all of the vegetation, including cover crops, found rooted inside the quadrat was clipped, roots and any sub-soil growth were removed, and vegetation was separated by species. Vegetation was dried at 35 °C for approximately three days and dry weight was recorded.
! 90
3.3.5.4 Weed management
In both years, the time needed for maintenance tasks in each treatment was recorded.
Maintenance time was incorporated into economic analyses of organic vineyard establishment.
String trimming was used under the vines in W, P, and W/P to limit the growth of competing vegetation. In year 1, string trimming occurred on August 11. In year 2, string trimming was measured in W, P, and W/P on 14 May, 14 June, 6 July, and 3 August. Each string trimming was completed within five days, depending on the number of available workers, which ranged from 1 to
3. String trimming occasionally caused accidental vine damage or death. Total vine death during the first season was approximately 5%, and 2% (28 vines) was caused by string trimming.
Hand weeding was used on between-row areas of ST and the in-row areas of WW as needed. Total time and number of workers were recorded to compare the potential economic viability of hand weeding in comparison to string-trimming and the Wonder Weeder. In year 1, hand weeding was used on 21 July and 13 August. In year 2, hand weeding occurred on 1 June, 29 June, and 11
August.
3.3.6 Statistical analysis
All data were subjected to analysis of variance. Main effects and interactions were tested for significance. Data with significant interactions of 2 or 3 factors had means separated overall all interacting factors. Means were separated using Tukey’s Honestly Significant Differences (HSD) at P
! 0.05. Data were analyzed using JMP®, a Macintosh compatible statistical software by SAS® (Cary,
NC).
3.4 Results
3.4.1 Soil testing and amendments
Soil test results showed the cation exchange capacity (CEC) of the vineyard soil to be 19.5
! 91 meq/100g. The calcium (Ca) level requirements is 67% CEC in a pre-plant field; the measured level was 44% CEC (8.6 Ca/19.5 CEC meq/100g). The magnesium (Mg) level requirement is 13% CEC, and the measured level was 7% CEC (1.4 Mg/19.5 CEC meq/100g). Nitrogen level was measured at
32 kg!ha-1 (29 lbs!A-1); the recommended level is 78 kg!ha-1 (70 lbs!A-1) (Table 3.1). Adequate phosphorus (P) and potassium (K) levels are 25 ppm and 250 ppm and the measured levels were 7 ppm and 158 ppm, respectively. All other measured nutrient levels including boron, zinc, manganese, copper, iron, sodium, total bases, and pH were adequate (Moulton and King, 2005).
3.4.2 Treatment effects on weed biomass distribution and composition in 2009
On August 3, the interaction between row location and treatment was significant for biomass measurements (Table 3.2). Total biomass (weeds plus cover crops) in-row for all treatments and between-row for W, P, and W/P ranged from 207.1 to 300.8 g!m-2. The in-row biomass mainly consisted of weeds and the between-row biomass consisted primarily of the cover crop. Weed biomass primarily consisted of common lambsquarters (Chenopodium album L.), shepherd’s-purse
(Capsella bursa-pastoris L.), smartweed (ladysthumb, Polygonum persicaria L., and pale smartweed,
P. lapathifolium L.), and henbit (Lamium amplexicaule L.). Total between-row biomass was lowest in
ST and WW (0.9 and 6.9 g!m-2) (Table 3.3), due to low weed and cover crop presence in these treatments. Of the annual cover crops, pea biomass in W/P was low and did not differ between-row and in-row (34 and 40 g!m-2, respectively), while nearly twice as much pea biomass was collected between-row than in-row in P (179.4 and 107.3 g!m-2, respectively). Similarly, wheat biomass collected in W and W/P was twice as great between-row as in-row (approximately 180 and 98 g!m-2, respectively). In general, more weeds were found in-row rather than between-row in all treatments.
All treatments produced a similar between-row weed biomass, ranging from 0.8 to 94.1 g!m-2. Weed biomass in W, P, and W/P ranged from 65.4 to 156.4 g!m-2 for in-row and between-row samples, and, except for in-row biomass in P, were all similar to between-row weed biomasses in ST and WW
(0.8 and 6.5 g!m-2, respectively). The greatest weed biomass was sampled in-row in WW and ST
! 92 (311.2 and 205.4 g!m-2, respectively).
On September 27, there was a significant interaction between collection area (i.e. in-row or between-row) and treatment for biomass measurements (Table 3.2). Total biomass collected in-row for all treatments and between-row for annual cover crop treatments ranged from 52.8 to 108.3 g!m-
2. Total between-row biomass was lowest in ST and WW (2.9 and 28.5 g!m-2, respectively) and consisted entirely of weeds. Peas were found at very low levels in-row in P and W/P (1.5 and 0.9 g!m-
2, respectively). Wheat biomass was twice as great between-row as in-row in W and W/P
(approximately 100 and 40 g!m-2, respectively). Weed biomass was greatest in-row in P and WW
(94.6 and 68.0 g!m-2, respectively). Except for ST, in-row and between-row weed biomass was similar for all treatments. In ST, more weeds were found in-row rather than between-row, although the magnitude of the difference was less pronounced than in August.
3.4.3 Treatment effects on weed biomass distribution and composition in 2010
On July 22, the interaction between row location and treatment was significant for clover, ryegrass, and total biomass (Table 3.3). Weed biomass primarily consisted of white clover (Trifolium repens
L.), Italian ryegrass (Lolium perenne ssp. multiflorum L.), common lambsquarters (Chenopodium album L.), shepherd’s-purse (Capsella bursa-pastoris L), smartweed (ladysthumb, Polygonum persicaria L., and pale smartweed, P. lapathifolium L.), and panicle willowweed (Epilobium brachycarpum L.). The greatest clover biomass was collected in-row in W/P and P (360.2 and 157.3 g!m-2, respectively). Clover biomass in all other treatments and collection areas ranged from 0.2 to
111.9 g!m-2. Ryegrass biomass was similar between-row and in-row in ST, W, P, and W/P treatments
(ranging from 0.1 to 158.9 g!m-2). However, eight times more ryegrass was found between-row in
WW than in-row. Ryegrass was either perennial (L. perenne L.) or annual (L. multiflorum LAmer.) and a distinction in the data was not made because distinguishing between the two was difficult.
Perennial ryegrass was part of the companion grass mix seeded in WW, whereas annual ryegrass was a weed. From this point forward, ‘ryegrass’ will be used to refer to both species for biomasses in
! 93 WW, but only the annual species in other treatments. The greatest total in-row biomass was in W/P and P (491.5 and 347.7 g!m-2, respectively), and the in-row biomass for P was also similar to between-row biomass of WW, W, P, and W/P.
In July, weed biomass was greater between-row (70.8 g!m-2) than in-row (36.2 g!m-2), and was marginally greater in the annual cover crop treatments (ranging from 60.8 to 97.1 g!m-2) than in ST and WW (ranging from 5.5 to 25.2 g!m-2) (Table 3.4). In September, the interaction between row location and treatment was significant for ryegrass and total biomass (Table 3.3). Ryegrass biomass was similar between-row and in-row (0.1 to 102.3 g!m-2), except for the WW treatment where more ryegrass was found between-row than in-row (175.5 g!m-2 and 22.2 g!m-2, respectively). The annual cover crop treatments had the greatest clover biomasses ranging from 121.2 to 205.7 g!m-2, and ST and WW had the lowest (6.6 to 43.4 g!m-2). Weed biomass was not significantly different amongst treatments on September 27.
3.4.4 Treatment effects on grapevine shoot growth in 2009
Weed management did not affect grapevine shoot length on July 30, but shoots were longer in WW and ST than in the annual cover crop treatments on August 13 and September 27 (Table 3.5 and
Figure 3.1). Shoots were longest at the end of the season in WW (66 cm) and shortest in W (11 cm).
In 2009, MA shoots tended to be longer than PNP; however the difference was not significant on
August 13. MA grew an average of 43.5 cm in 2009 while PNP grew approximately 42% less (25.6 cm). There was no interaction between weed control treatment and cultivar on July 30 or August 13, however there was an interaction on September 27 where PNP shoot length did not differ from MA in
W/P, while PNP shoots were shorter than MA in all other treatments.
3.4.5 Treatment effects on grapevine shoot growth in 2010
Weed management treatment significantly affected shoot length on all measurement dates in
2010 due to treatment and tended to be greater in ST and WW (Table 3.6 and Figure 3.2). The greatest growth over the season was in ST (125 cm) and the least growth was in W/P (58.5 cm). In
! 94 2010, MA shoot lengths were greater than PNP; however this difference was not significant on June
10. The overall mean growth for MA was 93.3 cm and for PNP was 29% less (66 cm).
3.4.6 Maintenance requirements
In 2009 and 2010, the annual cover crop treatments required the least amount of maintenance time (12.8-18.3 h!p-1!ha-1 and 51.9-66.2 h!p-1!ha-1, respectively) (Tables 3.7 and 3.8). The in-row area required 94% more time than the between-row area in 2009 (67.2 h!p-1!ha-1 and 3.5 h!p-1!ha-1, respectively) and 77% more time in 2010 (118.8 h!p-1!ha-1 and 27.7 h!p-1!ha-1, respectively). In
2009, more time was spent hand weeding ST and WW than on any other task (77.8 and 32.6 h!p-
1!ha-1, respectively). In 2010, the greatest percentage of time was spent string-trimming the annual cover crop treatments (41%, 42.5-66.8 h!p-1!ha-1), however the most time spent on a single task was hand weeding in ST (73.6 h!p-1!ha-1). There was no difference in maintenance requirements between grape cultivars.
3.5 Discussion
3.5.1 Weed control
Weed biomass in 2009 consisted mostly of annual species, which is common in vineyards during their first year (Baumgartner et al., 2008). The annual cover crops were able to compete successfully with between-row weeds because of their high seeding rate, and had greater biomass than the weeds throughout 2009, with the exception of P. As a result, weed presence was primarily in-row in
W, P, and W/P, and between-row in ST and WW where tillage was practiced and no cover crop was seeded in 2009. Tillage leads to increased numbers of annual weeds because upturning the soil exposes buried seeds to light and stimulates germination (Buhler, 1997). Similar trends in greater annual weed emergence after cultivation have been previously reported (Akemo et al., 2000;
Baumgartner et al., 2008; Ross et al., 2001; Sheaffer et al., 2002). Weeds grew in greater density where there was the least amount of competitive pressure. The annual cover crops were seeded both in-row and between-row, however the drip line supplied added water and nutrients to the in-row
! 95 areas only. Thus, in-row weeds were better supplied and competed better with the cover crops in- row. Pea and wheat cover crop biomass in-row and between-row were consistent with their seeding rate and placement.
In 2009, maintenance was implemented more frequently after August, which resulted in reduced weed biomass between-row in September as weeds were removed before they became established.
This was more so the case where no cover crop was planted (i.e. ST and WW), suggesting that cultivation reduced weed growth more than mowing. Between-row cover crop biomass also decreased from August to September, with wheat persisting longer than pea under this maintenance program. The cover crops were maintained by mowing between-row and string-trimming in-row.
Mowing is known to injure most broadleaf plants more than grasses since the meristematic region of grasses is below the blade level. Mowing apparently also injured pea more than the broadleaf weeds, because between-row weed biomass was greater in P than in W and W/P in September. Towards the end of the summer, the soil had dried significantly and became a physical barrier against germinating weeds, resulting in lower weed emergence and biomass.
The only cover crop that did not out-compete the weeds was pea. Weed biomass was greater than pea biomass in P in-row in August and September and between-row in September. This is consistent with results from Brennan and Smith (2003) and Daly et al. (1996) who found that a legume cover crop will have lower density and lower weed suppression ability. Furthermore, legume cover crops have relatively low early- and mid-season light interception, resulting in poor early season canopy development and weed suppression (Ross et al., 2001).
The lifespan of pea and wheat under these maintenance regimes was about three months. In
2009, cover crops were seeded in June and were nearly eliminated by September; in 2010, cover crops were seeded in March and were almost completely gone by July. White clover and ryegrass were the dominant species present in the vineyard by the summer of 2010. When cultivation is infrequent or absent, a shift from annuals to perennials in weed populations is often observed
(Derksen et al., 1993; Froud-Williams, 1998). It is well documented that Italian ryegrass has similar
! 96 growth habits and emergence time as winter wheat, as well as allelopathic characteristics, and often outcompetes wheat in cropping systems (Hashem et al., 1998; Justice et al., 1994; Kinfe and
Peeper, 1991; Liebl and Worsham, 1987; and Stone et al., 1998). White clover biomass was generally greater where pea was seeded, but ryegrass biomass did not differ among treatments or between row locations. Mowing during clover establishment is known to increase clover biomass by increasing light interception and decreasing competition from other vegetation, which can lead to an overall improvement in the clover’s weed suppression ability (Hiltbrunner et al., 2007; Ross et al.,
2001). However, increased mowing of clover can result in greater competition with the grapevines as well (Brandsæter et al., 1998), resulting in reduced shoot growth (Ross et al., 2001). This also explains the decrease in ryegrass biomass in treatments where white clover biomass increased.
Between-row cultivation in ST and in-row cultivation in WW kept white clover and ryegrass from establishing, and reduced annual weed biomass. According to Blum (1997), clovers can suppress broadleaf weeds more than grasses, which can be a beneficial aspect of cover crops in young vineyards.
Greater weed biomass was found in annual cover crop treatments than in ST or WW by July, and between-row weed biomass exceeded in-row biomass across all maintenance regimes. In-row areas of ST and WW were clean cultivated by hand and mechanically, respectively, whereas W, P, and W/P were string-trimmed. String trimming and mowing reduced weed growth but did not eliminate it whereas cultivation (ST in 2009 and 2010, and WW in 2009) provided more effective weed control.
Furthermore, string trimming appeared to have low efficacy on white clover given its prostrate growth habit and belowground growth (Thorsted et al., 2006). In consequence, weed biomass by September consisted mostly of white clover. Based on weed suppression ability alone, where low weed biomass is optimal, ST was the most effective treatment.
3.5.2 Grapevine growth
Grapevine growth was generally greatest with ST, followed by WW, and then by W, P, and W/P.
! 97 Between-row vegetation likely did not affect vine growth as much as in-row vegetation because grapevines were young and their root growth did not likely extend beyond the in-row area. Grapevine roots also tend to occur within the range of the drip-line emitters especially when fertigation is applied (Soar and Loveys, 2007). In 2009, when WW and ST were similarly maintained, vine growth was similar; but after ryegrass establishment in 2010, even though very little established in-row, vine growth in WW was less than in ST. In-row annual cover crops in W, P, and W/P reduced vine growth in WW more than the perennial cover crop. Bordelon and Weller (1997) found similar results with alleyway cover crops reducing vine growth more than a weed-free control. Conversely, Baumgartner et al. (2008) found that grapevine yield and growth was not affected by cover crops, provided a weed-free zone was maintained immediately around the vines. It should also be noted that this study used well-establish vines with an increased storage capacity for nutrients, which reduced the potential negative impact from cover crop competition. Based on vine growth alone, where maximum shoot length is desired, ST was the most effective treatment.
3.5.3 Maintenance
The most time-consuming maintenance task in this trial was hand weeding, accounting for 97% and 71% of the time spent on ST plots in 2009 and 2010, respectively. Although the vines grew almost twice as long in ST as in W, P, and W/P in both years, five times more time was spent on weeding in ST in 2009 and two times more in 2010. Based on maintenance time alone, where the minimum implemented time was preferred, W followed closely by W/P, was the most efficient treatment. Less maintenance time was spent in WW than ST in 2009, but similar times were spent in
2010 due to an increased usage of the Wonder Weeder. In 2010, two consecutive Wonder Weeder passes were needed to uproot ryegrass clumps in the first and second implementations. For the rest of 2010, the Wonder Weeder was only used in single passes as the ryegrass was kept at low densities so as to keep tough clumps from forming. If the Wonder Weeder had been implemented earlier in 2010, fewer passes may have been needed throughout that year and the overall
! 98 maintenance time may have been reduced. If this were the case, the maintenance time rank for WW would possibly have been number one and the overall rank for WW could have been greater than ST.
Failure to control weeds during vineyard establishment can also result in reduced vine growth and can delay fruit production for 1 year or more (Bordelon and Weller, 1997).
A comprehensive approach for ranking weed control treatments should include an analysis of primary factors involved: weed biomass, grapevine growth, and time spent on maintenance (Table
3.9). In this ranking system, weed biomass and shoot growth were of primary importance and were therefore given twice the power of maintenance time. Based on this scale, the treatments were ranked as (highest to lowest): ST > WW > W > W/P > P. Although ST, followed by WW, required the most time for maintenance, they also resulted in the lowest weed biomass and the greatest shoot length. Based on our results, an inverse relationship exists between weed biomass and time, and between vine length and weed biomass (Figure 3.5). That is, more maintenance time is required to reduce weed biomass, and lower weed biomass results in greater shoot growth.
3.6 Conclusions
In this study, weed biomass was reduced by the wheat and pea cover crops, but the vine growth was negatively affected by these cover crops likely due to in-row competition. All of the cover crops competed with the grapevines and reduced their growth. Future studies should include cover crops only seeded between-row. Wheat and pea did not appear to differ in their competitive ability with the weeds or the grapevines. Annual cover crops planted in mid-June were effective as weed suppressors through September, whereas annual cover crops seeded in March were effective only through June. The latter situation resulted in a niche replacement by summer perennials, which suppressed other species but also competed with the grapevines, and may be difficult to suppress in the future. Cultivation and hand weeding reduced weed biomass as compared to cover cropping and subsequent mowing or string trimming, but hand weeding accounted for the majority of maintenance time. In a newly established organic vineyard, the most effective and time efficient weed
! 99 management regime will likely include a vegetative-free zone maintained around the vines (i.e. in- row) using a specialty cultivator (e.g., Wonder Weeder) to minimize the time needed for in-row hand- weeding, and should start before ryegrass, or other noxious weed, clumps form. Further research is needed to identify best management practices for the between-row area, though cover crops appear to be effective at suppressing weeds with minimal vine competition in western Washington. A perennial cover crop in the between-row area is more likely to suppress annual weed species, and mowing may be more labor efficient and environmentally sustainable than cultivation and reseeding that would be needed for annual cover crops.
! 100
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AVA growing degree days. 30 December, 2010. ! 106 extension/weather/growing-degree-days/>. White, G.B. 1996. Chapter 9: Sustainability - the economics of converting conventionally managed vineyards to organic management practices. Acta Hort. Intl. Soc. Hort. Sci. 429:377-384. Zabadal, T.J. 1999. Pest control in small vineyards. Mich. St. Univ. Ext. Bul. 2698. Zabadal, T.J. and J.A. Andresen. 1997. Vineyard establishment: preplant decisions. Mich. St. Univ. Ext. Bul. 2644. ! 107 3.8 Tables Table 3.1 Soil analysis of organic vineyard prior to plant establishment at WSU Mount Vernon NWREC (2008). Suggested levels Nutrient Levels present Adequacy Amendments at pre-plantz Phosphorus (P) 7 ppm 25 ppm Low Bone meal Potassium (K) 158 ppm 200 ppm Low K-Mag Boron (B) <1.24 ppm 1-2 ppm Yes No Zinc (Zn) <5.1 ppm 2 ppm Yes No Manganese (Mn) 2.6 ppm 5 ppm Yes No Copper (Cu) 4.2 ppm 2 ppm Yes No Iron (Fe) <55 mg/kg N/A N/A No Calcium (Ca) 8.6 meq/ 100g 13.1 meq/ 100g Low Gypsum Magnesium (Mg) 1.4 meq/ 100g 2.5 meq/ 100g Low K-Mag Sodium (Na) 0.64 meq/100g <1.95 meq/100g Yes No Sulfur (S) <18 ppm N/A N/A No 7.9 ppm or 15-25 ppm or Nitrogen (N) Low Bone Meal (32 kg!ha-1) (61-101 kg!ha-1) Quality Slightly pH <6.8 6.0-6.5 Gypsum acidic Cation Exchange 19.5 meq/100 g N/A N/A N/A Capacity (CEC) ! zStiles and Reid, 1991; Moulton and King, 2005; Marx et al., 1996. ! 108 Table 3.2 Mean dry-weight biomass in organic weed control treatmentsz between or within grapevine rows in 2009. Pea Wheat Weeds Total 3-Aug. 27-Sept. 3-Aug. 27-Sept. 3-Aug. 27-Sept. 3-Aug. 27-Sept. Trt Between-row (g"m-2) y ST 0.0 c 0.0 c 0.0 c 0.0 c 0.8 c 2.9 d 0.85 b 2.9 c WW 0.0 c 0.0 c 0.4 c 0.0 c 6.5 c 28.5 bcd 6.9 b 28.5 bc W 0.0 c 0.0 c 179.4 a 105.8 a 89.6 bc 2.5 d 272.1 a 108.3 a P 179.4 a 0.0 c 0.55 c 0.0 c 94.1 bc 71.4 ab 300.8 a 71.4 ab W/P 40.0 c 0.0 c 181.0 a 99.5 a 65.4 bc 4.5 d 286.5 a 104.0 a In-row (g"m-2) ST 0.0 c 0.0 c 1.7 c 0.0 c 205.4 ab 52.8 abc 207.1 a 52.8 abc WW 0.0 c 0.0 c 1.3 c 0.0 c 311.2 a 68.0 abc 312.5 a 68.0 ab W 0.0 c 0.0 c 98.3 b 37.7 bc 118.0 bc 22.5 cd 216.2 a 60.2 abc P 107.3 b 1.5 a 1.2 c 3.2 c 156.4 b 94.6 a 264.9 a 99.4 a W/P 34.0 c 0.85 ab 98.8 b 54.5 c 126.7 bc 42.6 bcd 259.4 a 98.0 a ! z Weed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). ! 109 Table 3.3 Mean dry-weight biomass of weeds between or within grapevine rows under five organic weed control treatmentsz in 2010. Clover Rye grass Weeds Total 22-July 27-Sept. 22-July 27-Sept. 22-July 27-Sept. 22-July 27-Sept. Trt Between-row (g"m-2) y ST 0.2 b 0.0 NS 5.8 de 5.5 c 26.9 NS 40.6 NS 32.9 d 46.2 cd WW 13.3 b 79.5 NS 175.5 a 177.6 a 1.4 NS 0.5 NS 190.2 bcd 257.7 abc W 57.0 b 100.4 NS 37.2 cde 19.1 bc 124.1 NS 42.9 NS 220.1 bcd 162.4 bcd P 14.0 b 73.8 NS 118.7 abc 65.5 bc 90.3 NS 34.3 NS 223.2 bcd 173.7 bcd W/P 62.5 b 160.3 NS 50.3 cde 14.1 bc 109.3 NS 60.4 NS 224.8 bcd 234.8 bcd In-row (g"m-2) ST 0.5 b 13.2 NS 0.1 e 0.1 c 23.3 NS 19.6 NS 24.0 d 32.9 d WW 29.7 b 7.2 NS 22.2 de 6.0 c 9.5 NS 8.3 NS 61.4 cd 21.5 d W 111.9 b 238.4 NS 80.9 bcde 84.2 bc 70.2 NS 67.8 NS 263.0 bc 390.4 a P 157.3 ab 168.6 NS 158.9 ab 102.5 ab 31.2 NS 74.8 NS 347.7 ab 345.8 ab W/P 360.2 a 251.0 NS 85.2 bcd 63.6 bc 45.9 NS 49.5 NS 491.5 a 364.1 ab ! zWeed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! 110 Table 3.4 Mean dry-weight biomass of white clover and other weeds within five organic weed control treatmentsz in 2010. (g!m-2) Clover Weeds Treatment 22-July 27-Sept. 22-July 27-Sept. y ST 30.1 b 6.6 c 25.2 bc 30.1 NS WW 4.5 b 43.4 bc 5.5 c 4.5 NS W 55.4 ab 169.4 ab 97.1 a 55.4 NS P 54.5 ab 121.2 abc 60.8 ab 54.5 NS W/P 54.9 a 205.7 a 77.6 a 54.9 NS ! zWeed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! 111 Table 3.5 Mean grapevine shoot length for five organic weed control treatmentsz and two grapevine cultivarsy in 2009. Shoot length (cm) Treatment 30-July 13-Aug. 27-Sept. x ST 35.4 NS 52.1 ab 97.4 a WW 37.9 NS 55.8 a 103.9 a W 29.8 NS 34.4 c 41.4 b P 34.4 NS 42.0 bc 53.6 b W/P 33.0 NS 38.3 c 46.9 b Cultivar MA 42.3 a 55.2 NS 85.9 a PNP 25.9 b 33.8 NS 51.4 b ! zWeed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yCultivars are ‘Madeleine angevine’ (MA) and ‘Pinot noir précoce’ (PNP). xMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! ! ! ! 112 Table 3.6 Mean grapevine shoot length for five organic weed control treatmentsz and two grapevine cultivarsy in 2010. Shoot length (cm) Treatment 27-May 10-June 24-June 8-July 22-July 5-Aug. 19-Aug. x ST 35.4 a 49.5 a 63.2 a 85.2 a 110.9 a 136.3 a 160.4 a WW 31.1 ab 42.9 ab 56.9 ab 71.8 ab 90.6 a 103.9 b 124.8 b W 25.6 bc 35.6 bc 47.2 bc 57.0 bc 65.4 b 74.4 c 84.8 c P 29.5 abc 39.5 bc 49.6 abc 56.8 bc 66.5 b 78.9 c 91.2 c W/P 23.8 c 30.9 c 41.1 c 50.3 c 59.4 b 67.8 c 82.3 c Cultivar MA 30.5 a 41.5 NS 55.1 a 70.2 a 87.5 a 104.4 a 123.8 a PNP 27.6 b 37.9 NS 48.1 b 58.3 b 69.6 b 80.1 b 93.6 b ! zWeed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yCultivars are ‘Madeleine angevine’ (MA) and ‘Pinot noir précoce’ (PNP). xMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! 113 Table 3.7 Mean hours (h"p-1"ha-1) required for mowing, disking, Wonder Weeding (WW), hand- weeding (HW), string-trimming (STR) and all season-long maintenance tasks (Total), for five organic weed control treatmentsz and two grapevine cultivarsy in 2009. Treatment Mow Disk WW HW STR Total x ST NONE 1.90 NONE 77.83 a NONE 79.73 a WW 1.26 1.90 11.51 32.53 b NONE 47.20 b W 1.26 NONE NONE NONE 11.51 b 12.77 c P 1.26 NONE NONE NONE 17.09 a 18.35 c W/P 1.26 NONE NONE NONE 17.09 a 18.35 c Row area Between-row 2.03 1.51 NONE NONE NONE 3.53 b In-row NONE NONE 4.59 44.14 18.30 67.06 a zWeed! control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yCultivars are ‘Madeleine angevine’ (MA) and ‘Pinot noir précoce’ (PNP). xMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! 114 Table 3.8 Mean times (h"p-1"ha-1) of mowing, disking, Wonder Weeding (WW), hand-weeding (HW), string-trimming (STR) and all season-long maintenance tasks (Total) for five weed-control treatmentsz and two grapevine cultivarsy in 2010. Treatment MOW DISK WW HW STR Total x ST NONE 30.60 NONE 73.61 a NONE 104.20 a WW 9.56 NONE 58.22 13.44 b NONE 81.21 ab W 9.56 NONE NONE NONE 42.48 a 52.04 b P 9.56 NONE NONE NONE 56.74 a 66.29 b W/P 9.56 NONE NONE NONE 52.73 a 62.29 b Row area Between-row 15.29 12.25 NONE NONE NONE 27.54 b In-row NONE NONE 23.29 34.83 60.79 118.9 a zWeed! control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). yCultivars are ‘Madeleine angevine’ (MA) and ‘Pinot noir précoce’ (PNP). xMeans followed by the same letter within columns are not significantly different (Tukey’s HSD, P ! 0.05). NS=nonsignificant. ! 115 Table 3.9 Ranking of organic weed control treatmentsz, based on total weed biomass, grapevine shoot growth and maintenance time (2009-2010). Whole number rankings scaled were: 1 = superior and 5 = unacceptable. Weed Suppression Grapevine Growth Time Requirements Total Weed Total Final Shoot Avg. Overall Trtz Biomass Rank Rank Maintenance Rank Length (cm) Rank Rank (g!m -2) Time (h!ha-1!p -1) ST 24.21 1 160.4 1 5 1.80 1 183.94 WW 28.22 2 124.77 2 4 2.40 2 128.41 W 34.94 4 84.83 4 1 3.40 3 64.81 P 43.56 5 91.23 3 3 3.80 5 84.64 W/ 32.78 3 82.3 5 2 3.60 4 P 80.64 z! Weed control treatments were standard cultivation between-row and hand-weeding in-row (ST), in- row tillage with Wonder Weeder and grass seeded between-row (WW), winter wheat cover crop seeded at 335 kg!ha-1 and in-row string-trimming (W), Austrian winter pea cover crop seeded at 335 kg!ha-1 and in-row string-trimming (P), and winter wheat and Austrian winter pea cover crop mix seeded at 224 kg!ha-1 and 112 kg!ha-1, respectively (W/P). ! 116 3.9 Figures 140 MA-ST 120 MA-WW 100 MA-W MA-P 80 MA-W/P PNP-ST 60 PNP-WW Shoot growth (cm) growth Shoot 40 PNP-W PNP-P 20 PNP-W/P 0 7/27 8/6 8/16 8/26 9/5 9/15 9/25 Date Fig. 3.1 Effect of weed control treatmentz on Madeleine angevine (MA) and Pinot noir précoce (PNP) grapevine shoot-growth on 30 July, 13 August, and 27 September in 2009. zStandard treatment (between-row (BR) cultivation, in-row (INR) hand-weeding) (ST), Wonder Weeder (Harris Manufacturing, Burbank, WA) treatment (BR companion grass, INR tillage with cultivator) (WW), winter wheat cover crop treatment (BR-seeded at 335 kg!ha-1, INR string-trimming) (W), Austrian winter pea cover crop treatment (BR-seeded at 335 kg!ha-1, INR string-trimming) (P), winter wheat and Austrian winter pea cover crop treatment (BR-wheat seeded at 224 kg!ha-1 and pea seeded at 112 kg!ha-1, INR string trimming) (W/P). 117 180 160 MA-ST MA-WW 140 MA-W 120 MA-P MA-W/P 100 PNP-ST 80 PNP-WW Shoot growth (cm) growth Shoot 60 PNP-W PNP-P 40 PNP-W/P 20 0 5/23 6/12 7/2 7/22 8/11 Date Fig. 3.2 Effect of weed control treatmentz on Madeleine angevine (MA) and Pinot noir précoce (PNP) grapevine shoot-growth on 26 May, 3 and 23 June, 7 and 21 July, and 4 and 18 August in 2010. zStandard treatment (between-row (BR) cultivation, in-row (INR) hand-weeding) (ST), Wonder Weeder (Harris Manufacturing, Burbank, WA) treatment (BR companion grass, INR tillage with cultivator) (WW), winter wheat cover crop treatment (BR-seeded at 335 kg!ha-1, INR string- trimming) (W), Austrian winter pea cover crop treatment (BR-seeded at 335 kg!ha-1, INR string- trimming) (P), winter wheat and Austrian winter pea cover crop treatment (BR-wheat seeded at 224 kg!ha-1 and pea seeded at 112 kg!ha-1, INR string trimming) (W/P). 118 40 35 ) 30 2 Weeds 25 Ryegrass 20 Clover 15 Dry-weight (g/m biomass 10 Wheat 5 Peas 0 Jul-10 Jul-10 Jul-10 Jul-10 Jul-10 Jul-10 Aug.-09 Aug.-09 Aug.-09 Aug.-09 Aug.-09 Aug.-09 Sept.-10 Sept.-10 Sept.-10 Sept.-10 Sept.-10 Sept.-10 Sept.-09 Sept.-09 Sept.-09 Sept.-09 Sept.-09 ST WW W P W/P Treatmentz Fig. 3.3 Mean weed and cover crop biomass in five organic weed control treatmentsz in 2009- 2010. zStandard treatment (between-row (BR) cultivation, in-row (INR) hand-weeding) (ST), Wonder Weeder (Harris Manufacturing, Burbank, WA) treatment (BR companion grass, INR tillage with cultivator) (WW), winter wheat cover crop treatment (BR-seeded at 335 kg!ha-1, INR string- trimming) (W), Austrian winter pea cover crop treatment (BR-seeded at 335 kg!ha-1 , INR string- trimming) (P), winter wheat and Austrian winter pea cover crop treatment (BR-wheat seeded at 224 kg!ha-1 and pea seeded at 112 kg!ha-1, INR string trimming) (W/P). 119 160 140 120 100 80 MA 60 PNP Shoot length (cm) length Shoot 40 20 0 ST WW W P W/P Treatmentz ! Fig. 3.4 Mean shoot lengths for organic weed control treatmentsz and cultivars Madeleine angevine (MA) and Pinot noir précoce (PNP) on 27 September 2009. zStandard treatment (between-row (BR) cultivation, in-row (INR) hand-weeding) (ST), Wonder Weeder (Harris Manufacturing, Burbank, WA) treatment (BR companion grass, INR tillage with cultivator) (WW), winter wheat cover crop treatment (BR-seeded at 335 kg!ha-1, INR string-trimming) (W), Austrian winter pea cover crop treatment (BR-seeded at 335 kg!ha-1, INR string-trimming) (P), winter wheat and Austrian winter pea cover crop treatment (BR-wheat seeded at 224 kg!ha-1 and pea seeded at 112 kg!ha-1, INR string trimming) (W/P). ! ! ! 120 Shoot Growth Vine High Maintenance ! !"#$ ! Biomass Weed %&'()*(&(+* ! ! Time for Maintenance ! Fig. 3.5 Three-way relationship between weed biomass, shoot growth, and maintenance time based on generalized results. ! 121