Progress report for SW23-956
Project Information
Limited water availability is a major issue in the western US. Leap et al. (2017) demonstrated profitable dry farmed tomato production in coastal California, and suggested that dry farmed tomatoes have improved flavor. The WSARE project, “Production and Marketing of Dry Farmed Tomatoes in Oregon” has demonstrated that dry farm tomato production is possible in the Willamette Valley using blossom end rot (BER) resistant varieties and grafting. However, many BER resistant varieties and grafted tomatoes were rated lower than ungrafted BER susceptible tomatoes like 'Early Girl' in overall preference during sensory evaluations.
Farmers want to grow flavorful tomatoes with low rates of BER. This project will create a “BER Toolkit” for farmers. All of these tools are based on Saure’s hypothesis that BER is the result of a sequence of luxurious growth followed by severe stress (Saure, 2014). We will test the effectiveness of the following "tools":
- Sheltering
- Soil amendments
- Decreased in-row spacing
- Deficit-irrigating transplants prior to planting
The toolkit will be disseminated to farmers through field days, publications, and videos made available on the Dry Farm Collaborative Youtube page. Farmers will understand all of the benefits and drawbacks of each “tool” and will be able to test a suite of them. A diversity of vegetable producers will be able to apply the principles of the BER toolkit to their farms whether irrigated or dry farmed.
Determining how to successfully dry farm ‘Early Girl’ tomatoes in the Willamette Valley will open up a high value market while reducing water use and increasing in-stream flows. It will eliminate the need for costly irrigation systems, increase profitability, and reduce greenhouse gas emissions. It will allow farmers on lands with no or limited irrigation rights to grow profitable crops with little to no risk, thereby increasing profitability and quality of life.
- Test and demonstrate a suite of "tools" for mitigating blossom end rot (BER) in dry farmed tomato production, all based on the Saure Hypothesis that BER is caused by a sequence of early season luxurious growth followed by severe stress.
- Tool 1: Sheltering by intercropping with dry farmed corn to reduce drought stress.
- Tool 2: Reducing soil amendment applications to reduce early season luxurious growth.
- Tool 3: Decreasing in-row plant spacing to reduce early season luxurious growth.
- Tool 4: Pre-stressing seedlings during nursery production to produce transplants with "Drought Stress Memory."
- Determine effects of tools on other measures of yield, fruit quality, wind run, cost of production, and plant health.
- Determine the interactive effects between the different tools.
- Demonstrate the effectiveness of the BER toolkit when implemented on farms.
- Educate farmers and agricultural professionals to different theories of the cause of BER in tomatoes.
- Educate farmers and agricultural professionals to the components of the BER toolkit (including grafting), how they effect crop production, and how they interact.
- Promote dry farmed tomatoes and educate the consumers, retailers, wholesalers, and other marketers to the value of dry farmed tomatoes, including environmental benefits and culinary value.
Cooperators
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Research
The tools in the BER toolkit were selected because they have been shown to reduce BER incidence in trials conducted from 2019-2022. The tools were based on the hypothesis presented by Saure (2014, 2001). Saure hypothesized that BER was the result of a sequence of a) rapid growth that predisposes fruit to BER followed by b) severe stress that results in cell death at the fruit’s blossom end (in the case of dry farming this would be drought stress). Therefore, the tools aim to either reduce drought stress or prevent rapid early season growth. The treatments are:
- Reducing drought stress by sheltering the crop from the wind – Rows of corn were planted to the north of plots to reduce wind run through the tomato crop.
- Reducing rapid early season growth by limiting soil amendment application – this included a reduced amendment treatment (50 lbs of N per acre) and a no amendment treatment.
- Reducing rapid early season growth by decreasing in-row spacing and increasing between row spacing – We reduced the in-row spacing from 2’ 6” to 1’ 8” and the between-row spacing increased from 6’ 0” to 9’ 0”.
- Trellising – We trellised plants using a basket weave. We hypothesized that trellising would increase BER incidence and drought stress by elevating the crop and exposing it to the wind.
To test the effects of the treatments, two trials were conducted. The first was at the Oregon State University Vegetable Research Farm (VRF), and tested five treatments (sheltering, reduced amendment, no amendment, in-row spacing, and trellising) against a control. The treatments are detailed in Table 1.
The second set of trials were conducted on commercial farms throughout the mid-Willamette Valley. These trials tested the effect of fertilizer application on diverse sites to determine an optimum application. These treatments were the same as the no amendment, reduced amendment, and control treatments from the VRF trial. Each of the five farms had one replication of these three treatments.
Additionally, six farmers independently trialed the BER toolkit. For these trials the farmers selected with of the tools that they wanted to trial against a control. They recorded their observations in a survey that we provided.
Table 2 shows the effect of the different treatments on yield and fruit quality for dry-farmed tomato grown at the OSU Vegetable Research Farm. Treatments did not differ in total yield. Treatments did different in marketable yield, with the trellised treatments having higher marketable yields than the no amendment treatment, the control, and the sheltered treatment. Trellising also resulted in larger fruit than any other treatment. Treatment impacted BER incidence, with the reduced amendment treatment having lower BER than the control treatment. It should be noted that there was incredibly low BER incidence in the OSU Vegetable Research Farm trial. Treatment did not affect incidence of yellow shoulder, but it did affect incidence of sunscald. The trellising treatment had the lowest and reduced in-row spacing treatment had the second lowest incidence of sunscald.
Results of the on-farm trials are presented in Table 3. Treatment did not affect mean total yield or mean marketable yield. However, it should be noted that at one of the on-farm trials, there was a substantial increase in yield when fertilizer was applied. This field was former pasture and had very low phosphorus concentration. Thus, it is possible that on certain sites, fertilizer does improve yields. Treatment did affect average fruit size, with the no amendment treatment having larger fruit than the control. Fertilizer application treatment affected incidence of yellow shoulder; the control had half the yellow shoulder incidence than the no amendment treatment. Treatment also affected soluble solids concentration (sugar) with the control having a higher soluble solids concentration than the no amendment treatment.
Site data is presented in Table 4. Farms differed considerably in soil and climate characteristics. Most farms had an available water holding capacity (AWHC) of 8 inches or greater. AWHC is important when dry farming, as the amount of water the soil can hold correlates with total yield. Some farms had almost no wind while others were very windy. Some farms had very little soil fertility while others were extremely fertile.
Finally, six farms trialed the BER toolkit independently. We did not collect yield or fruit quality data on these sites, but they do offer an opportunity to see what farmers thought about the treatments. Three of the six farmers reported that the tools that they implemented resulted in a decrease in BER. The other three farms reported no effect. One farm that had found reduced BER from the corn shelter also had lower marketable yields from the corn shelter. This was due to the shelter blowing over onto the tomato crop during a storm. Farmer survey data is presented in Table 5.
BER incidence at the OSU Vegetable Research Farm was very low this growing season, and this may explain why we were not able to detect many treatment difference. We believe that the low BER incidence at the Vegetable Research Farm was due to the plant being less drought stressed, though we are unsure why they were less drought stressed this year than in previous years. Low BER was not the only way that the VRF trials differed from the on-farm trials. There was also higher yields, larger fruit, a higher incidence of yellow shoulder, and fruit had lower SSC. This may have been the result of careful soil prep in addition to lower soil fertility. However, we were able to detect an effect of some of the treatments. We will present the effect of each of the treatments.
Sheltering – Sheltering with blocks of corn did not appear to have much of an effect on BER in tomato at the OSU Vegetable Research Farm in 2023. This may be in part because the corn plots were too small to block the wind effectively. Wind run was also active from south and west. However, additional plots within the control and sheltering treatments were harvested in an attempt to test the effect of distance from the corn on BER incidence. While distance from the corn did not affect BER incidence, when all of these plots were included in the analysis a small but statistically significant effect was detected (1.2% BER in sheltered plots vs. 1.6% BER in the control plots). Italian dry farmers reportedly intercrop tomatoes with corn (Castronuovo et al. 2023).
Fertilizer application – The effect of fertilizer application was tested in both on-farm trials and at the OSU Vegetable Research Farm. We found some interesting results. First, increasing fertility appears to increase incidence of BER but it also decreased incidence of yellow shoulder. The optimum amount of fertility to add is probably site dependent, with current soil nutrient levels and degree of sheltering from the wind having some effect. Fertilizer application also affected fruit weight and soluble solids concentration. It may be that increasing fertilizer application causes plants to use water less efficiently, and that the decrease in fruit size and increase in soluble solids concentration is a result of the plants being more drought stressed.
In-row spacing – Decreasing the space between plants decreased the incidence of sunburn. Because the plants were closer together, it is possible that fruits were better covered by foliage.
Trellising – These plots had the best results, with higher marketable yields, increased average fruit size, and reduced sunscalding. Trellising may have prevented sunscald by improving coverage. Plants that were allowed to sprawl would occasionally have vines break under the weight of the fruit, allowing light to penetrate the canopy. We expected that trellising would increase BER incidence, but this result was not observed.
Research Outcomes
Dry farming has been widely adopted for certain crops in the Willamette Valley of Oregon, and this is increasingly true for vegetables. However, dry-farmed tomato growers continue to struggle with physiological disorders, including BER, yellow shoulders, and sunscalding. OSU researchers have shown that some of this effect can be mitigated by site selection, variety selection, and vegetable grafting. In this project, we have focused our attention on management practices. If farmers are able to control physiological disorders in dry-farmed tomato, this will help them profitably produce crops without irrigation. This will improve their livelihoods while also reducing the burden on surface and ground water resources.
The project team continues to believe the in efficacy of the BER toolkit as a management strategy for reducing BER in dry-farmed tomato. Sheltering the crop from the wind is expected to decrease crop drought stress, increase marketable yields, and reduce BER incidence. Optimum fertilizer is site dependent, though on most sites excess fertilizer results in an increase in BER. Fertilizer applications affect other tomato quality measures, including incidence of yellow shoulders, average fruit weight, and soluble solids concentrations. Planting rows at a tighter in-row spacing appears to reduce incidence of sunscalding. Finally, trellising increased marketable yields and average fruit weight. However, it is still possible that by elevating the crop it is more exposed to the wind, which may increase drought stress.
In 2024, we are going to focus on testing the interactions between the different treatments. To do this, we will conduct large trials at research farms and in on-farm trials. We will also test how seedling production practices affect dry-farmed tomato success. Large trials will consist of eight plots. Four of these will be sheltered by corn (or sunflowers) and four will be exposed to the wind. The tomato plots will be planted on the leeward side of the corn. Density and fertility treatments will be planted in a 2x2 factorial design.
Education and Outreach
Participation Summary:
Of those surveyed, 16/17 reported that they now understood that there are multiple theories regarding the direct causes of BER.
Of those surveyed, 4/17 reported that they intended to grow dry-farmed tomatoes after learning about our project. An additional 8/17 reported that they already grew dry-farmed tomatoes and 4/17 reported that they did not grow dry-farmed tomatoes, but intended to before they learned about the project.
Of those who said that they had grown dry-farmed tomatoes before:
6/8 said that they were interested in using sheltering to control BER
7/8 reported that they were interested in applying fewer soil amendments to control BER
7/8 reported that they were interested in planting at a different spacing to control BER, while 1/8 wanted to see more data
1/8 reported that they were interested in using tomato grafting to control BER, while 1/8 wanted to see more data
3/8 were interested in pre-drought stressing seedlings to create drought stress memory, while 3/8 wanted to see more data
Of those whose had not grown dry farmed tomatoes before:
6/8 were interested in growing a shelter crop to prevent BER, while 1/8 wanted to see more data
6/8 were interested in applying fewer soil amendments to control BER, while 2/8 wanted to see more data
6/8 reported that they were interested in planting at a different spacing to control BER
1/8 reported that they were interested in using grafting to control BER
4/8 reported that they were interested in pre-drought stressing seedlings to create drought stress memory, while 2/8 wanted to see more data.
Of those who grow dry-farmed tomatoes, 4/8 report that they already market dry-farmed tomatoes, 1/8 reported that they intended to market dry-farmed tomatoes before seeing the presentation, and 2/8 reported that they intended to after seeing the presentation.
Of those who did not grow dry-farmed tomatoes, 1/8 reported that they intended to market dry-farmed tomatoes before seeing the presentation and 5/8 reported that they now intend to market dry-farmed tomatoes after learning about the project.
Of those surveyed, 7/17 were interested in using the marketing materials to help them sell dry-farmed tomatoes.
In summary, of all those who filled out a survey, 16/17 reported that they intended to change a practice, whether that was adopting one of the tools or growing or marketing dry-farmed tomatoes.
Education and Outreach Outcomes
Farmers are open to the learning about alternative theories as to the direct causes of BER. Unfortunately, many publications on the physiological disorder strictly focus on the theory that calcium deficiency is the direct cause. Even if this theory is ultimately more correct, it may cause farmers to pursue solutions that have no effect on their crop. For example, those who promote the calcium theory of BER often claim that while calcium is the direct cause of BER, this is not due to insufficient calcium in the soil. Instead, BER is due to their being insufficient water to move the calcium, an excess of other cations, or some other factor that is limiting calcium uptake and allocation to the fruit. However, when a farmer hears that calcium is the cause, they will assume that they can fix BER by adding more calcium to the soil. We propose that rather than focusing on generalizable theories, those who conduct educational and outreach activities should focus on presenting methods that actually control BER and help to educate farmers on the contexts in which these practices actually work.
In the case of our project, we promote treatments like sheltering to control BER. We hypothesize that sheltering will reduce wind, which will in turn reduce evapotranspiration and drought stress. However, there are contexts in which sheltering will have little effect. One of our on-farm trials was an urban farm with very little wind measured (see Table 4, Monmouth). At this farm, planting a shelter will probably have no effect on BER incidence. However, this site had relatively high BER, likely induced by the large amount of compost that had been applied to the field. Thus, for this farmer, we would recommend reducing the amount of fertilizer and compost applied, or opening a new field where there is lower organic matter.
In summary, our aims are to help farmers understand practical tools that they can use to manage physiological disorders, rather than confusing them with theory. We also want to contextualize these tools so farmers understand the conditions that make each of them appropriate.
- Methods of dry-farmed tomato production.
- Multiple theories on the direct causes of BER.
- Tools of the BER toolkit and their efficacy.
Farmers were taught methods of field prep, amendments, planting, and crop management for dry-farmed tomatoes. Of the farmers who completed the survey, eight reported that they grew dry-farmed tomatoes, four reported that they did not grow dry-farmed tomatoes but wanted to grow them prior to learning about the project, four reported that they intend to grow dry-farmed tomatoes after what they learned from the project, and one reported that they did not intend to grow dry-farmed tomatoes.
Of the farmers surveyed, 16 reported that they now had a better understanding of the multiple theories as to the direct causes of BER and one reported being more confused about the causes of BER after learning about the project.
After learning about the project, 12 farmers reported that they wanted to try growing a shelter crop, 13 farmers reported that they wanted to try reducing the amendments they apply, 13 reported wanting to plant dry-farmed tomatoes at a tighter in-row spacing, two farmers reported that they wanted to graft tomatoes to reduce drought stress, and seven farmers were interested in trying to prestress seedlings in the nursery prior to planting.