Dr. Terry Bates of the Lake Erie Regional Grape Program (LERGP) at the Cornell Lake Erie Research and Extension Laboratory (CLEREL) was host to an “on-the-fly” variable rate demonstration at the Wednesday, May 10, 2017 LERGP Coffee Pot Meeting. The extension team holds Coffee Pot meetings every Wednesday during the growing season from early May through the end of July. These meetings are hosted by growers across the Lake Erie Grape Belt, on their farms and in their barns. The LERGP Extension team provides only the coffee and donuts, the agenda is usually set by grower questions. This provides an informal setting for exchange of information and ideas, as well as a means to apply current research results to the issues of the growing season.
The May 10 Coffee Pot meeting was different in that it was held at CLEREL, and was started with a demonstration of a portion of the research being conducted as part of the USDA/NIFA SCRI Efficient Vineyard project. Dr. Bates explained that vineyards can be scanned using NDVI technology (Normalized Difference Vegetative Index) which shows the amount of photosynthetic (green) matter in the vineyard at the time of scanning. During the early season, this accounts for the shoots that are just emerging from the canes and are approximately 2-3 inches in length. With this map in hand, the grower can go into the vineyard and validate the information in each of the zones (i.e. how many shoots are in a low vigor zone or a high vigor zone) by counting the number of shoots on the vines in each of the zones. The shoot numbers can be applied back to the NDVI map and a shoot count map can be created. With this map, and the right technology, a grower can input the data into a field computer in their tractor which will then control the hydraulics of the shoot thinner. The map provides the computer with vigor zones from low to high causing the shoot thinning head to speed up to remove a higher percentage of shoots in the high vigor zones, and where there are less, the shoot thinner will slow down and remove less shoots. The goal of this on the fly variable rate shoot thinning is to create a uniform vine size across the vineyard block optimizing production.
At this meeting, the 30 growers in attendance were shown how the shoot thinner responds to the maps without operator involvement. Rhiann Jakubowski, GIS technician with LERGP, created a “fake map” of the parking lot so the attendees would be able to see how the thinning heads sped up or slowed down according to the zones from the map. The tractor operator then drove through the vineyard providing growers a firsthand look at variable rate shoot thinning. For growers in the Lake Erie region, if you are interested in taking the first step toward variable rate management, please contact a member of the LERGP extension team to set up an NDVI scan of your vineyard.
This is the second year that we have been able to perform on-the-fly variable rate shoot thinning and we are excited to see the results as the season progresses. For more information about the Efficient Vineyard project, please visit our website at efficientvineyard.com. To learn more about the Lake Erie Regional Grape Program you can visit our website at lergp.com.
Executive Summary: Outreach and Adoption Showcase Meeting - Efficient Vineyards USDA/NIFA SCRI Project - June 16, 2016
One of the objectives of the Outreach and Adoption team for the USDA/NIFA SCRI project, Efficient Vineyard’s, is to determine the current knowledge base of grape growers regarding the use of spatial data for variable rate vineyard management, as well as identify the preferred learning styles of growers. A survey was created and disseminated to the members of the project team for review. A total of 181 surveys have been completed by growers, members of the grape industry, as well as members of the Efficient Vineyards advisory committee. Fifty-eight growers completed a hard copy version of the survey at a California meeting conducted by Kaan Kurtural, 40 growers participated during “Coffee Pot” Meetings held in the Lake Erie grape belt of New York and Pennsylvania, 16 members of the advisory committee participated and 67 responses were collected via an on-line version of the survey using Survey Monkey. Participation in the survey was concentrated in California, New York and Pennsylvania but the on-line survey allowed for participation by growers from 15 additional states.
Survey results indicate that the members of the advisory committee are good representatives of the growers participating in the survey as comparing responses of the two groups showed they were very similar. An identified shortcoming of the survey results is that the table grape industry is underrepresented. We are currently working with project team members representing this industry group to increase participation.
Baseline information shows that there is a need for better promotion of the USDA/NIFA SCRI Efficient Vineyards project to improve the realization that the project exists as well as what the projects’ goals are and how they might be used in their vineyard operations. This is not an unexpected response as we are in the first year of the project.
When asked if vineyard blocks, or portions of vineyards of the same variety are currently being managed differently, survey participants overwhelmingly replied that they did manage blocks and vineyards differently. However, when asked how they determined the variability in a vineyard to allow them to apply management practices differently, personal observation was the number one answer for all groups taking the survey. Survey results showed sensors as being only 25% as likely to be used in making variable rate management decisions as personal observations. These responses are good indicators that this project can have an impact at the vineyard level.
The survey showed that manual labor remains an important component of implementing variable rate practices. The majority of responses showed that variable rate practices are currently implemented primarily through the use of manual labor while manual adjustment of mechanized practices was the second most reported practice. This projects’ goal of using GPS or other automatic adjustment of mechanized practices is being used in a very small number of vineyards represented by this survey.
When asked about the preferred method of obtaining vineyard management information, it was not unexpected that there was no clear information transfer method selected by respondents. Newsletters and field meetings were the most often selected methods but internet resources and email were also well represented. It was interesting to see that when asked how they would like to receive sensors maps, responses by members of the California grape industry were almost totally by computer or smartphone, whereas New York and Pennsylvania responses showed there is still the desire by a significant number of growers for paper copies.
Variability in vine vigor was the information identified as the number one piece of information growers would like to see via sensor mapping followed by yield maps, water status of vines and variability of soils.
Current users of sensor maps reported that they find them mostly, to sometimes, reliable but also report that maps or data are difficult to interpret and costs are high. Participants also indicated that both lowering costs and increases in quality were thought to be benefits of addressing variability in the vineyard. These answers identify a real opportunity for this project. Developing a system to efficiently collect, create and distribute spatial data maps that can then be used to apply mechanized variable rate management will address the concern of maps being difficult to interpret and should provide the data needed to show any improvements in fruit quality and profitability.
A follow up survey will be conducted in the final year of the project to determine impacts on a grower level.
Take Home Messages
- The Efficient Vineyard Advisory Committee is representative of the grape industries involved in the project.
- Personal observation is currently the most commonly used method for determining the need for implementing variable rate management. This shows a significant opportunity for showing an impact through the implementation of collecting spatial data using sensors.
- Manual labor is currently the most common form of implementing variable practices in vineyards. This signifies another opportunity for significant impact through the implementation of spatial mapping linked to variable rate equipment.
- Lowering costs and improving quality are seen by survey participants as the reasons for implementing variable rate practices.
- While California growers embrace the use of computers and smart phones to access spatial data mapping, an educational effort is needed in New York and Pennsylvania to move growers from paper copies to allow them to take full advantage of the maps in the implementation of variable rate management.
Outreach and Adoption Survey - June 2016
As a part of our Outreach and Adoption portion of the Efficient Vineyard SCRI project, a survey was conducted to assess the grower population’s initial perception/awareness of the project and the processes involved with it. It also seeks to find the best methods to distribute information to growers and others interested in this project. The following graphs represent the responses received from the various sources as indicated.
Seasonal Concord Fruit Development in the Lake Erie Region
Understanding fruit development is important in Concord grape production because fruit is the final agricultural product delivered to be processed into juice and other grape products. Payment to producers is based on fruit yield and juice soluble solids. Controlling crop size in relation to vine size is critical in delivering the highest possible yield of quality fruit. Fruit set and development is influenced by biological and environmental factors and it is important to understand and track how the crop is developing to make appropriate crop control management decisions. This article discusses Concord fruit development from bloom through the three stages of berry growth to harvest during the 2017 season.
Concord Fresh Berry Weight
Each growing season, Concord fresh berry weight is collected from a standard set of “phenology” vines maintained at the Cornell Lake Erie Research and Extension Laboratory in Portland, NY. The curve represents the 18-year mean in berry weight (error bars = standard deviation). Tracking the current season berry weight in relation to the long-term mean assists with a more accurate crop estimate.
Concord Bloom: 6/14/2017
This season, the staff at CLEREL recorded trace bloom in the standard phenology vines on 6/11/2017 and official bloom (50% cap fall) on 6/12/2017. The Concord flower cluster in this image is at over 90% full bloom on June 14th.
Most of the wild grapes you see on the roadside or in the woods have either all male or all female flowers. However, most of the cultivated grape varieties we grow have “perfect” or “hermaphrodite” flowers. Interestingly, cultivated grapes are also highly self-pollinated because the pollen will go from the anther to the stigma before the cap pops off. To catch and rehydrate the pollen, the stigma produces a sap (seen at the tip of the stigma arrow in the picture). Rehydration of pollen takes about 30 minutes and then the pollen uses stored starch in the pollen grain to grow down the style. The speed of pollen tube growth and the time it takes to reach the ovule is related to temperature (roughly 48 hours at 60 degrees F, 24 hours at 70 degrees, and 12 hours at 80 degrees). The colder it is, the slower the pollen tubes grow. Since the ovules are only receptive for a short time, cool weather during bloom can cause the pollen to miss the window and lead to poor fruit set.
Concord Pre-Fruit Set: 6/16/2017 (left) and Concord Mid-Shatter: 6/19/2017 (right)
Just after flowering, the pollinated pistils on the grape clusters will start do develop but not all of the ovaries will successfully develop into fruit. This Concord cluster has about 100 developing ovaries but will only retain and develop 25-30 fruit, on average. Expanding pollen must first fertilize at least one of four ovules while they are receptive. Successful fertilization induces the production of certain plant growth hormones for cell division (auxin) and cell expansion (gibberellin) in different tissue layers. The balance of these hormones is important for the successful retention of the developing ovary. Percent total fruit set is influenced by cultivar and certain management practices, such as pruning level. A variety of environmental stresses (light, temperature, carbohydrate, nutrient, and water stress) can also reduce fruit set. Many of our management recommendations, such as for weed control and mineral nutrition, aim to eliminate any vine stress during the fruit set and berry cell division phase in the 3-4 weeks after bloom. Unfertilized or stressed ovaries will eventually abscise or “shatter.”
Just one week after the start of bloom, Concord clusters are setting fertilized berries and dropping others. This cluster has dropped about 40% of the pistils which were originally pollinated but not successfully fertilized. A corky abscission scar can be seen where the pedicel of aborted flowers have separated from the rachis (cluster stem).
Why is it important to track fruit set?
Current research objectives aim to improve mid-season crop estimation. Grape yield is a function of shoots/vine, clusters/shoot, berries/cluster, and final berry weight. These “yield components” can be influenced by biological factors such as vine size and vine water status, management factors such as pruning level, or environmental factors such as temperature during fruit set. Spatial data from the Efficient Vineyard project illustrate how yield components can vary from vineyard to vineyard as well as within a vineyard. We are testing the use of the Carnegie Mellon Image sensor to directly detect and count certain yield components – such as shoot number and berry number across a vineyard. We are also combining this information with other spatial data to direct vineyard sampling during the middle of the growing season to predict final crop size across whole vineyard blocks.
Concord 30 Days After Bloom: 7/12/2017
After bloom and fruit set, Concord berries enter a growth phase of both cell division and cell expansion. At 4-weeks post-bloom, Concord berries will reach approximately 50% of their final fresh weight but will still be in the middle of the rapid fruit growth (stage I). Berry size and weight in a cluster, vine, or vineyard varies at both 30 days after bloom and at harvest (as seen in the photo). Variation in berry growth is a function of both cell number (through cell division) and cell size (through cell expansion) – and these are controlled by both biological and environmental factors.
The developing seeds produce auxin, cytokinin, and gibberellin and it is the balance of these hormones which influences the amount of cell division and expansion in the fruit. A berry with more seeds will tend to be larger than one with fewer seeds because of the seeds’ influence on cell division and expansion. While all parts of the fruit are developing during stage I, it is the division and expansion of the mesocarp (flesh or pulp) that makes up most of the berry volume. Environmental factors, such as water availability, will also influence berry weight at 30 days after bloom by influencing cell expansion – again primarily in the mesocarp tissue. Cell number will double two times during stage I through cell division. In addition, cell volume will increase through cell wall loosening and the expansion of cell vacuole volume. Presumably, the cell division hormone, cytokinin, diminishes through stage I, which slows cell division as the berries enter the lag phase of berry growth (stage II).
Concord 45 Days After Bloom
At 45 days after bloom, Concord berries are between 60-65% final fresh weight and are entering stage II of berry development. This stage is also referred to as the lag phase and will last until veraison (approximately 69 days after bloom in Lake Erie Concord). Lag phase is dominated by seed development and maturation. By veraison, the seeds will reach their final size and lignify in preparation for dispersal. The growth of the mesocarp and exocarp slows during the lag phase. Again, it is the balance of plant hormones, such as auxin, cytokinin, and abscisic acid, which controls the cell division and expansion in berry tissues and prevents the seeds from germinating too early.
Concord Fresh Berry Weight Development: Beginning of Stage III. During stage III, the cell walls of the mesocarp change physically and chemically to soften and accumulate water and sugar. The seeds turn brown from tannin accumulation and harden through desiccation and become ready for dispersal. Veraison also triggers the accumulation of anthocyanins (purple pigments) in the grape skins (exocarp).
In Stage III of berry development from veraision to harvest, the seeds finish maturing and the fruit ripens to attract animal feeding for seed dispersal. Just before veraison, the berries are hard and green with relatively high organic acid (30 g/L) and low sugar concentrations (7.5 oBrix). Over a four to five week period from veraison to harvest, Concord fruit will become soft and dark purple with relatively low organic acid (10 g/L) and high sugar concentrations (16 oBrix). In Lake Erie Concord, veraison occurs 69 days after bloom, on average. Veraison may start a few days earlier in warm, dry years with moderate vine water stress and lower berry weight and it may be delayed in cool, wet seasons with high vine water status and larger berries. Veraison marks a physiological change in the fruit characterized by a rapid increase in water and sugar accumulation in the mesocarp (flesh) and anthocyanin accumulation in the exocarp (skin). There is also a degradation of organic acids and chlorophyll and the fruit will become soft as the cells walls of the mesocarp change and weaken.
Typical ripening concentration curves of juice soluble solids (left) and juice titratable acidity (right) in Lake Erie Concord. Desired fruit chemistry for producing single strength juice is 16 oBrix (+/- 0.5) and 1.0-1.1% (10-11 g/L) titratable acidity at approximately 30-40 days post-veraison. Environmental conditions (precipitation, sunlight, temperature) as well as viticulture management (crop load) can influence berry weight and the rate of sugar accumulation.
Concord Ready for Harvest
At approximately 100 days after bloom, Concord seeds are fully mature and the fruit has reached the right sugar, acidity, color, and texture to be eaten by animals and promote seed dispersal. In the processing industry, we use these attributes to harvest and process the fruit into grape juice. Most of the water, natural sugar, and fruit acidity can be pressed out of the mesocarp. The deep purple pigments are primarily in the grape skins and need to be extracted during processing to give Concord products the characteristic purple color. After juice processing, Concord seeds can also be collected, dried, and pressed to extract grapeseed oil.