Mitigation of Vineyard Greenhouse Gas Production Using Organic Floor Management Approaches

This project represents an overarching effort to develop accurate metrics for vineyard carbon footprints under two widely used organic treatments. The project coordinates with efforts by Dr. William Salas (Applied Geosolutions LLC) and Alison Jordan of the Wine Institute to calibrate the DeNitrification DeComposition model (DNDC). The model will be embedded into decision support systems (DSS) providing trending analyses for use by practitioners for carbon and energy assessments (https://metrics.sustainablewinegrowing.org/). The modeling exercises will allow us to test multiple management practices in order to lessen (mitigate) N2O emissions from California vineyards. The data is being made available to Dr. Alissa Kendall and Sonja Brodt of the Department of Agricultural and Environmental Engineering and Agricultural Sustainability Institute to assemble life cycle analyses for carbon footprints of vineyards. In this report we outline mechanistic studies undertaken to understand microbial processes and therefore better calibrate the DNDC model.

Interaction of Rootstock, Mechanical Crop Load Management Systems and Differential Regulated Deficit Irrigation on Mineral Nutrient Requirements of Wine Grapes in Southern San Joaquin Valley

Grapevine leafroll disease causes non-uniform maturation of fruit in Vitis vinifera, including poor color development in red grape varieties. The disease causes losses of as much as 20-40{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}, with delays of 3 weeks to a month in fruit maturation. To date 5 different viruses, namely Grapevine leafroll associated virus (GLRaV) types -1 through -4, and -7, have been conclusively shown to be associated with leafroll disease. In the case of GLRaV-4, several distinct leafroll disease-associated virus strains have been identified within the virus species. This project was planned as a detailed study of the effects of these viruses on cultivar Cabernet Franc grapevines. This grapevine produces a readily scored foliar response to leafroll virus infection. The analysis includes challenges with each agromonically significant GLRaV species, including types -1 and -2 (2 isolates each), -3 (3 isolates), -4, -5, -7 and -9 (one isolate each). Also, pairwise combinations of GLRaVs -1, -2, -3, -5 and -7 are being tested. The test vines are grafted onto a broad selection of different rootstock varieties. Nine different rootstocks are involved in the test, including AXR #1, Mgt 101-14, 110R, 3309C, 5BB, 420A, Freedom, St.

George 15 and St. George 18. 15 replicates for each treatment are divided into three separate blocks each (5 replicate per treatment per block). The project has thus-far revealed a spectrum of differences in infection symptoms attributable to the different virus species, and to different combinations of these viruses and the grapevine varieties they infected. For example, it was observed that leaf symptoms produced by GLRaV-3 were more severe than those produced by GLRaV-4. In another example, it was found that GLRaV-2 induced more severe reactions on vines propagated specifically on rootstocks Freedom and 5BB. Those test vines exhibited red leaf symptoms, short internodes, and a near-lethal decline in vigor. Detailed analysis of these and other specific aspects of leafroll disease are on-going. In 2014, the vine performances were evaluated by measuring the trunk diameter, cane length, pruning weight, yield and fruit composition.

Trunk diameter analysis did not show much differences on each rootstock treated with different GLRaVs and virus isolates. For cane length measurements, the data showed that St. George 15 and St. George 18 rootstocks were not affected by different treatments. However, the two different isolates of GLRaV-2 (2B and 2C) had significant impact on cane length of plants propagated on rootstocks 101-14, 3309C, 5BB and Freedom. The yield did not show any significant difference between different treatments on rootstocks 110R, 420A, 5BB, AXR, Freedom, St. George 15 and -18. Pruning weight analysis did not show any differences between different treatments and rootstocks 110R, 420A, St. George 15 and -18. However, significant differences were observed between different treatments and the rootstocks 101-14, 3309C, 5BB and Freedom. Rootstock AXR was less affected. The analysis also showed that both GLRaV-2 isolates (2B and 2C) in general have been more severely affected the plants on panel of rootstocks.

Developing and Evaluating Social Networking Tools for Viticulture

We sought to 1) determine how familiar our academic and industry colleagues were with blogs, Facebook, and Twitter, and provide training for them if necessary, 2) extend more viticulture information through social networking tools, and 3) develop some metrics to learn how often the tools were used, and by whom. Surveys distributed separately to core clientele, viticulture specialists and advisors in California, and out¬of¬state extension faculty, suggested that many academic and industry colleagues were potentially interested in using social networking tools to extend and receive viticulture information, but they needed training to learn how to use them, particularly in a professional context. Therefore we provided social media training at several meetings throughout the state. Perhaps due in part to our training efforts, our sites have steadily attracted more users over time; the number of people who ?like? our Facebook page has increased from 93 people in January 2010 to 249 people in January 2011, and our followers on Twitter have increased from 182 last January to 357 this January. Further, our blog was accessed nearly 50,000 times in 2010 and, in December 2010 alone, our Facebook page was accessed more than 11,000 times. We dramatically increased the content provided in 2010. For example, we sent 87 ?tweets? in 2009 versus 272 tweets in 2010. In 2010 we also began to use special software that allowed us to integrate, to some extent, our social media tools. This provided content at varying levels of detail and may have helped us expand our reach. We intend to further extend our reach by developing other types of content including video and pictures which can be shared on specialized social sites such as YouTube, and Flickr, respectively. Monitoring social media is complex, but we?ve learned that our sites are regularly accessed by men and women of a wide age range, from at least 20 different countries. The social aspect of these sites, especially Twitter, has facilitated sharing of information beyond our immediate users, thereby expanding their impact.

Developing Sustainable ‘In-Row’ Management Practices for Improving Weed Management and Soil Nitrogen Retention

The goal of this research is to develop alternative ‘in-row’ weed management practices that both provide effective weed management, do not negatively impact grapevine growth and juice, and improve soil nitrogen (N) retention by minimizing inorganic N leaching and nitrous oxide (N2O) emissions. The establishment of ‘in-row’ treatments was initiated in October 2009. Greenhouse gas emissions (N2O and carbon dioxide, CO2) were collected bimonthly, and C and N dynamics in response to events that increase greenhouse gas emissions were measured from October 2009 to the present. These measurements will continue through the study’s third year. Preliminary findings indicate that ‘pulse’ events such as cultivation, compost addition, fertigation, irrigation and rainfall are major periods of greenhouse gas emissions. When cultivation occurred just after compost addition, N2O and CO2 emissions increased and were greater than the cover crop and herbicide treatments. When rainfall occurred immediately after this cultivation, N2O and CO2 emissions were also greater than the other treatments, highlighting the interactive effects of management (i.e., cultivation and compost) and rainfall on greenhouse gas emissions. When treatments were irrigated, both N2O and CO2 were greatest from the cultivated treatment, followed by the cover crop and herbicide treatments, respectively. Although the cultivated treatment emitted more GHGs, further analysis will determine the net carbon footprint of each respective treatment. The cover crop and herbicide treatments tended to have greater nitrate leaching than the cultivated treatment. Temporal dynamics of leaching differed among treatments, suggesting that management practices could be adjusted over time to minimize these losses. Data from this study will be incorporated into the GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network) database to develop predictive models of greenhouse gas emissions in response to agricultural management. GRACEnet is a national network of USDA/ARS scientists who develop “…agricultural practices that will enhance carbon sequestration in soils, promote sustainability and provide a sound scientific basis for carbon credits and trading programs work on greenhouse gas emissions in agricultural operations across the nation”. This project compliments the study funded by the CDFA Specialty Crops Block Grant program (SCBG) (“Reducing Our Footprint: Minimizing Greenhouse Gas Emissions and Nitrogen Leaching in Vineyards, and Enhancing Landscape Carbon Stocks”). Furthermore, findings from this study will be included in the development of an interactive process model for grower use assessing GHG emissions associated with different management practices, a project that was recently awarded to the California Sustainable Winegrowing Alliance by CDFA SCBG (“Field Testing a Carbon Offset and Greenhouse Gas Emissions Model for California Wine Grape Growers to Drive Climate Protection and Innovation”).

Evaluation of the Impacts of in-row Vineyard Floor management Practices on Soil & Water Erosion, Vine Growth & Productivity, Weed Control and the Economics of Wine Grape Production

One large-scale experiment and two small plot experiments have been established to evaluate the impact of in-row barley cover cropping on soil and water erosion, vine growth and productivity, weed control, and the economics of wine grape production. A 3.5-acre experimental site is evaluating three in-row management practices. The in-row treatments evaluated are:

  1. Standard, pre-emergent herbicide using flumioxazin (Chateau®) at 0.38 lbs a.i./acre + 2{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} glyphosate with follow-up post emergence applications of 2{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} glyphosate applied as needed in the summer to control escaped weeds.
  2. Standard + polyacrylamide (PAM) applied in a band under the vine row @ 3 lbs per acre prior to rain events with weed control as described above.
  3. In-row cover crop using barley that was allowed to develop to 12 inches and then burned back with a 2{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} glyphosate application.

Two small plot experiments were established, one to evaluate the influence of timing of burn-back herbicide sprays to in-row covers and the second to evaluate the use plant type for in-row cover cropping.

Investigations on a Necrotic Union Disorder of Pinot Noir/11OR Grapevines

Although RT-PCR assays of diseased collections were positive for RSPaV and RVFV,
the same viruses were also detected in non-diseased collections. Thus, there was no
apparent correlation between them and necrotic union disease.

Regarding the red leaf grapevines of PN777 putatively grafted on rootstock 101-14. With
the grower?s consent (because cost of analysis was anticipated), roots from both the red
leaf- and the green leaf-grapevines were submitted for DNA analysis at FPS. Test results
identified both diseased grapevines as 110R and the healthy grapevine as 101-14.
Evidently, a mixture of two rootstocks was planted in the block. Anecdotal observations
suggest further that the rootstock 101-14, unlike 110R, is likely tolerant of the putative
agent of necrotic union and that infected, asymptomatic grapevines of PN777/101-14
may have served as internal reservoirs of a causal agent. Also and perhaps a larger
question looms in that what impact might the causal agent of 110R necrotic union have in
infected asymptomatic scions on 101-14. Does it affect berry maturation or soluble solid
composition, e.g. delays sugar accumulation, pigmentation, etc?

In Trial 2005, the lack in development of necrotic union symptoms was not surprising. It
has been our experience that wood markings require, minimally, two-year incubation;
vis-à-vis stem lesion disease. We anticipate union symptoms to develop in 2007 in the
test plants inoculated in Trial 2005. Likewise, union symptoms in Trial 2006 are
anticipated in 2008.

Rapid spread had continued in the Carneros West block and less so in the south Napa
District. This suggests that a putative vector species was more active in one area, then in
the other. Secondary spread is hypothesized because necrotic union symptoms have
developed on large mature grapevines. If infected nursery stocks were planted, they
should remain small in stature with weak growth and/or succumb.

The standard cloning procedure is laborious and inefficient in cloning viruses in lowcopy
numbers. Our laboratory has struggled with this problem for quite some time.
However, we now have access to the Genome Sequencer 20tm, which can sequence 1000s
of cDNAs and should enable us to obtain sequences for the necrotic union agent (see
details in 2007-2008 proposal).

Organic Farming Practices and Conventional Farming Practices: Fruit/Wine Quality and an Economic Comparison

Two newly planted Cabernet Sauvignon vineyards were chosen for this study, one in Paso Robles and the other near Bradley in southern Monterey County. Each site consisted of a 40-acre parcel dedicated to organic production adjacent, but not co-mingled, with a conventionally farmed vineyard that employed recognized best farming practices. Vineyard Professional Services is responsible for the daily operations of the vineyards. Cal Poly personnel are responsible for cost analysis and research associated with this project in conjunction with VPS. The first year of this study was devoted to establishing the vineyards and preparing spreadsheets to analyze costs associated with organic and conventional winegrape production on the Central Coast. These vineyards are in warm region III-region IV climatic zones. Grow-tubes were employed at each site. Each vineyard operation was logged, recorded, and costs assigned for both sites. Vines were allowed to reach the fruiting wire and training has begun.Powdery mildew pressure is moderate in these locations, and none was noted on the plantings. Conventional sulfur dusting was employed with both locations for establishment years. Both vineyards were also planted to winter cover crops and mowed. Discing was not employed beyond planting. Measurements were not made concerning vine growth, but visual assessment did not detect differences, which was expected.The second year of this study will continue to focus on economics associated with this study. The major problem to be solved is water treatment. Well water used as irrigation source is high in carbonates, a condition traditionally handled with sulfuric acid addition. Sulfuric acid is not allowed in organic production, so alternative sources for water treatment are being explored. Dusting sulfur, the backbone of organic powdery mildew protection, is also being scrutinized more closely by regulatory agencies. Alternative materials approved for organic production will also be studied this year.

Organic Farming Practices and Conventional Farming Practices: Fruit/Wine Quality

Two newly planted Cabernet Sauvignon vineyards were chosen for this study, one in Paso Robles and the other near Bradley in southern Monterey County. Each site consisted of a 40-acre parcel dedicated to organic production adjacent, but not co-mingled, with a conventionally farmed vineyard that employed recognized best farming practices. Vineyard Professional Services is responsible for the daily operations of the vineyards. Cal Poly personnel are responsible for cost analysis and research associated with this project in conjunction with VPS. The first year of this study was devoted to establishing the vineyards and preparing spreadsheets to analyze costs associated with organic and conventional winegrape production on the Central Coast. These vineyards are in warm region IE-region IV climatic zones. Grow-tubes were employed at each site. Each vineyard operation was logged, recorded, and costs assigned for both sites. Vines were allowed to reach the fruiting wire and training has begun. Powdery mildew pressure is moderate in these locations, and none was noted on the plantings. Conventional sulfur dusting was employed with both locations for establishment years. Both vineyards were also planted to winter cover crops and mowed. Discing was not employed beyond planting. Measurements were not made concerning vine growth, but visual assessment did not detect differences, which was expected. The second year of this study will continue to focus on economics associated with this study. The major problem to be solved is water treatment. Well water used as irrigation source is high in carbonates, a condition traditionally handled with sulfuric acid addition. Sulfuric acid is not allowed in organic production, so alternative sources for water treatment are being explored. Dusting sulfur, the backbone of organic powdery mildew protection, is also being scrutinized more closely by regulatory agencies. Alternative materials approved for organic production will also be studied this year.

Optimal Viticulture Systems Comparison

For the 1997 season, several changes in the specific objectives of this project were implemented at the request of cooperators with Fetzer Vineyards. The modifications reflect an interest in generating research-based information which would be readily applicable to grape growers whose vineyard practices include a broad array of activities (i.e., from essentially organic to more conventional practices). Beginning with the 1997 season, the Optimal Viticulture Systems project included/the following three studies: 1) management of berm vegetation, 2) alternative control of powdery mildew, and 3) interrelationship of factors involved in mite pest problems. Unfortunately, since the decision to modify the project was not finalized until late in the spring, it was not possible to implement the berm management and powdery mildew components of the project during 1997. The third study in the Optimal Viticulture project focuses on a multifactored analysis of vineyard parameters associated with high density mite areas as compared with factors found in relatively mite-free areas in a given vineyard. Two vineyards (Chardonnay and Zinfandel) were selected for collection of data on mite population levels, site characteristics, vine water relations, and vine productivity. Both vineyards have demonstrated a history of mite problems occurring in various areas. These locations were designated as hot (mite pressure) and cold (no mite pressure) sites. Early in the season, a total of 18 locations in the Chardonnay vineyard and nine locations in the Zinfandel vineyard were surveyed to identify appropriate plots for the mite/vine stress study. In the Chardonnay vineyard, there appeared to be an inverse pattern of mites being heavier on foliage of hot site vines, while Erythroneura leafhopper nymphs were more abundant on foliage of cold site vines. Data from the Zinfandel vineyard revealed no consistent patterns of numerical differences for either mites or leafhoppers. The Chardonnay vineyard had statistically significant differences in yield and grapevine water relations for the 1997 season. Yields were highest for the cold sites. This can be attributed to both higher cluster weights and an increased number of berries per cluster. However, the treatments had no significant effect on fruit composition. Grapevine water relations were significantly affected by level of mite pressure in 1997. Cold sites had higher stomatal conductance and transpiration in the Chardonnay vineyard. On the other hand, the Zinfandel vineyard showed no statistically significant differences for yield, fruit composition and grapevine water relations. In conclusion, significant differences in viticultural performance were noted between hot and cold sites in the Chardonnay vineyard. Numeric differences were observed for mite populations but the differences were not statistically significant. A greater level of replication may have resulted in more clear cut results. To this end, in 1998, the focus of the study will shift to the Chardonnay vineyard and additional data collection sites have been added. Further research is needed to determine the factors involved in the observed differences.

Optimal Viticulture Systems Comparison

The dual experimental constraints of only two years of data collection (1995 and 1996) and relatively few differences among patterns of viticultural practices applied to the three types of treatment plots (i.e., organic, biologically-intensive, conventional) suggest the wisdom of extreme caution in attempting to draw biologically meaningful conclusions from results thus far in the study. However, several patterns of numerical trends indicate directions in which experimental results appear to be progressing. Total soil nitrogen analysis demonstrated differences of only 0.006{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} between 1995 and 1996, along with a nearly identical tight range of data grouped by treatment for 1996 (0.005{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}), as well as for 1995 and 1996 combined (0.006{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}). Data for soil microbiology activity indicates that conventional plots had higher biomass levels than organic or biologically intensive plots. Overall, one should be safe in concluding that no substantially significant differences across treatment plots for the soil chemistry and microbiological parameters as measured in this study were revealed through the 1996 sampling period. Nutritional status of the vines was greatly reduced from the adequate levels expressed during 1995. Nitrogen levels were half of their 1995 levels while magnesium, zinc, and manganese levels showed increases over 1995 levels. There was never any significant differences between nutrient levels in any of the treatments. During 1995 and 1996, arthropod data were collected for the herbivorous western grape leafhopper (Erythroneura elegantula), along with a wide array of natural enemies (i.e., predators and parasitoids), at approximately two-week intervals. With WGLH nymph densities throughout both 1995 and 1996 generally averaging well below 5 per leaf, very little differences between treatments could be reliably detected. The slowly developing grapevine canopy yielded very few beneficial arthropods sampled by leaf counts in 1996. A tremendous number of spiders were collected by pitfall trap sampling in this study during.1996: over one-half million (508,017) spiders were recorded! However, of the half-million spiders trapped in 1996, nearly 95{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} (3265/3456) belonged to the family Lycosidae, commonly known as wolf spiders and virtually never being found in the grapevine canopy itself. Thus, although these highly abundant lycosid spiders are most certainly generalist predators, the prey upon which they were feeding in 1996 most likely was limited to small soil-dwelling arthropods, which may themselves have had little distinct involvement (good or bad) with the grapevine canopy proper.