Dry Farm Melon Production in Oregon

Background Information
Literature review: In a study conducted in Jordan (Al-Mefleh 2021), deficit-irrigated muskmelon (single variety, unspecified) were shown to have smaller fruit and lower total soluble solids (TSS) than fully irrigated melons. In addition, deficit irrigation in some years reduced fruit firmness. In a Turkish study (Akhoundnejad and Dasgan 2019) of nine melon varieties shown in previous studies to have drought tolerance, varietal dry farm performance (yield and quality) varied significantly. The two highest performing varieties had significantly higher yield and TSS when dry-farmed than when grown with full irrigation. For other varieties, yield and TSS were lower when dry-farmed. 

Flavor: The Dry Farming Collaborative, led by Garrett, conducted a watermelon demonstration in 2019 in which they compared the flavor of dry-farmed and irrigated watermelons with a focus on varieties considered to be high performing when dry-farmed. Consumer taste tests of these watermelons indicate that dry farming can increase watermelon sweetness. The proportion of tasters who rated dry-farmed Blacktail Mountain watermelon as being “very sweet” was 25% higher than for the same variety irrigated, while for Cream of Saskatchewan it was 160% higher.

Tomato variety evaluations: Our group screened more than 225 varieties of tomatoes for dry farm performance in 2020 and 2021, resulting in the identification of 30+ high performing varieties (OPs and F1s, including red, dark, pink, yellow, and paste, and grafted scion/rootstock combinations), only one of which had been identified as a productive dry farm variety previously (summary at https://tinyurl.com/dryfarmtomatosummary2021). Our tomato work and the Turkish study indicate that the first step in developing a dry farm melon system is screening large numbers of cultivars (both OPs and F1s) under dry farm conditions to identify the top performers (yield, quality, shelf-life), as varieties vary dramatically in their dry farm performance.

Planting density: The optimal planting density for dry farm crop production is largely unexplored, and is likely both crop- and site-dependent. Historic dry farm crop production wisdom recommended very low planting densities to increase per-plant water availability (Creswell and Martin 1998). However, the Bay Area Early Girl dry-farm tomato system is planted as intensively as intensive drip irrigated systems (Leap et al 2017). In 2019, we evaluated the effect of planting density on the marketable yield of dry-farmed Early Girl tomatoes; an intensive 20 sqft per plant spacing was most productive, as blossom end rot incidence (which renders fruit unmarketable) decreased and fruit number (per acre) increased as planting density increased (Davis et al., 2023).

Preliminary melon data collection: Our group conducted preliminary melon variety trials at the OSU research farm in 2021 to develop production and data collection protocols (five watermelon varieties: four OP, one F1; five muskmelons: three OP, two F1; two honeydews: one OP, one F1). Small plot watermelon yields varied from 24 to 67 T/A, muskmelons from 17-36 T/A, and both honeydews yielded 52 T/A. While these yields are preliminary as they are from a single (very hot) summer and are extrapolated from small plots (some without borders), the yields fall in or above published irrigated yield ranges for muskmelon and watermelon (Hartz et al 2008; Lukas et al 2020), suggesting that dry-farmed melons are a promising dry farm crop that could be grown in rotation with dry-farmed tomatoes.

Grafting of dry farm tomatoes:
In our dry-farmed tomato work across two years, Fortamino and DRO141TX were shown to be very high performing rootstocks. As an example, on average, the rootstock DRO141TX increased yields by 110%, fruit size by 42%, and reduced BER incidence by 81% in a trial at the OSU vegetable research farm. Grafting had no effect on fruit firmness. Grafting can make cultivars such as BHN871 (an F1 orange slicer that is not high performing when dry-farmed ungrafted) high performing; grafting on Fortamino resulted in a 92% increase in yield, a 34% increase in fruit size, and a 96% decrease in BER incidence in an OSU experiment station trial. See the last table in the variety trial summary (https://tinyurl.com/dryfarmtomatosummary2021) for comparative grafted and ungrafted tomato yields from five on-farm trials.

Grafting of dry-farmed melons:
Grafting of melons has been widely shown to reduce soil borne disease severity and increase yield (Jang 2014) and fruit firmness (Kyriacou et al 2016). Only one paper (Yavuz 2021) was found on the impact of grafting on melon yield and quality when grown under drought conditions.  A single scion/rootstock combination was evaluated, and for that combination, grafting did not significantly change melon yield or quality when grown under irrigated or drought conditions.

Project partner Log House Plants grafts tomatoes. They tried to graft melons but it is difficult so they no longer do so, and instead purchase grafted plants from their partner Plug Connections (see Log House Plants letter). Project farm Gathering Together routinely grafts all of their tomatoes for soil borne disease management; they tried grafting melons, but were unsuccessful. We successfully grafted ten melon varieties onto the rootstock Flexifort in 2023.

Objectives:

Building on past and ongoing efforts, this project will:

Objective 1: Engage farmers in development, delivery, and evaluation of project

Objective 2: Identify productive dry-farmed melon varieties and/or rootstock/scion pairs

Objective 3: Evaluate the effect of planting density on yield

Objective 4: Market and promote dry-farmed melons

Objective 5: Engage other farmers in project outcomes

Objective 6: Evaluate project outcomes

Objective 1: Engage farmers in development, delivery, and evaluation of project

Year 1 (2022)
This project is a logical next step from the dry farm tomato project, and four of the farmers in this project were also involved in the tomato project. These farmers have a strong interest in and commitment to dry farming, and have conducted two on-farm tomato trials and participated in tomato project meetings and farmer field days. Project farmers worked with Stone and Davis to identify cultivars to include in the 2022 variety trial. They participated in the project farmer field day to evaluate, taste, and identify promising cultivars.

Year 2 (2023)

Farmers worked with Stone and Davis to identify cultivars to include in the 2023 variety trial. They hosted on-farm cultivar trials, participated in the project farmer field day to identify and describe promising cultivars, were present at project presentations, and participated in the final winter project evaluation.

Objective 2: Identify productive dry-farm melon (watermelon, muskmelon, and honeydew) varieties and/or rootstock/scion pairs

Year 1 (2022):
41 cultivars were evaluated at the OSU vegetable research farm, including:

• cultivars historically dry-farmed in CA and OR
• farmer partner favorite cultivars
• cultivars recommended by seed companies
• ungrafted plants of the cultivars that will be grown as grafted plants (listed below)

Scion/rootstock evaluations
Because melon grafting is considerably more difficult than tomato grafting, and ungrafted plants are unlikely to be produced by farmers in the near term, in 2022 the project evaluated grafted scion/rootstock combinations (rootstock ‘Shintoza’) formerly offered by Plug Connection (see project partner Log House Plants letter).

• Cantaloupe: Ambrosia
• Watermelon: Sugar Baby 

Site and soil selection – In 2022, we trialed 41 melon and watermelon cultivars at the Oregon State University Vegetable Research Farm, outside of Corvallis, OR. The soil there is a Chehalis silt loam with more than 12 inches of available water holding capacity (AWHC) in the first five feet. We believe that this may be one of the best soils for dry farming in the Willamette Valley. However, a plowpan was present on the site and may have limited yields in the 2022 season (our tomato trial, planted in the same field, had much lower yields than in previous years). This may explain why melon yields were lower compared to our data from 2021. 

Transplants – We had a lot of success starting melons indoors and then planting them out about a month later. Melons used for the trials were seeded on 4/13/2022, and a second “back-up” seeding occurred on 4/25/2022 (some of these plants were used as border plants and to fill plots if plant establishment was low). We used 200 cell flats with cells that were 2 ¼” deep. Temperature of germination chamber was kept between 75 and 80^oF. Plug mix used was Pro-Mix BX. Trays were subirrigated to prevent splashing and keep seedlings growing straight. Mike Hessel (Advisor Representative) insisted that melon seeds be planted with the pointy end upright as this ensures that the cotyledons can easily break free from the seed coat.

Planting – Melons were planted on 5/27/2022. Soil was loosened using a garden fork and then transplants were planted using a Pottiputki. The ground was firmed up around the base of the transplant. Transplants were subirrigated prior to planting and then were watered in with about a liter of water after planting.

Spacing – We have found that 7 feet between rows and 4 feet in row spacing works really well for melons and watermelons. The 7 ft between row spacing is about as wide as you can go and still lay a layer of 12 ft row cover over them to protect them from striped and spotted cucumber beetle.

Fertilizer – Fertilizer was applied on 5/24/2022. Nutririch (4-3-2) was applied at 1100 lbs/acre and pelletized feathermeal (12-0-0) was applied at 630 lbs/acre. This was about half of the fertilizer that we had originally intended to apply. Fertilizer was incorporated using a powerharrow after it was applied.

Weeding – The field was kept clean using Allis-Chalmers Model G tractors, hoes, and wheel hoes.

Harvest – We harvested melons twice a week, on Monday and Thursday, starting on 8/15/2022 and ending on 9/26/2022. During the final harvest, melons that were almost ripe (would have ripened in the next week) were also collected. Harvest data for these melons was not included in the total yield data, however it was included in the continuous figures as a final harvest on 9/29/2022 (see report for figures).

Handling and Storage – After harvest, melons were moved to a cool, dark location to finish ripening. 

Sensory Evaluations – During the growing season we convened two different panels to evaluate melons, one of retailers/marketers and the other of farmers. Unfortunately, we were not able to test more than five cultivars at each event as tomato sensory evaluations were the main objective of these panels.

Year 2 (2023):
Research station trial: 70 cultivars (22 from 2022 high performing cultivars), ten cultivars grafted onto Flexifort rootstock, a planting density trial, and a succession trial were grown by Stone/Davis at the OSU research station 'Vegetable Research Farm', with harvest frequency and measurements as in 2022.

On-farm trials: Project farmers, with Stone and Davis assistance, conducted four on-farm trials in year two. These were plantings of ten melon varieties. In addition, ten farmers grew a single replication of the melon 'Lilly'. Project staff collected borings from each of the four main on-farm trials and Andy Gallagher, soil scientist, described the profile and quantified its available water holding capacity (AWHC), an important predictor of the site’s dry farm suitability and productivity.  

Each of the four on-farm trials grew five plants of each of the ten (in one instance six) cultivars at 28 sqft per plant (7 ft between rows and 4 ft in-row), and border rows were planted on either side of the trial. For the farms located near OSU, OSU staff collected harvest data. Harvests occurred once a week and measurements were the same as at the research station experiments.

Research station and on-farm data were collected and interpreted using mixed effects modeling with cultivar as the fixed effect and farm as the random effect. This allowed for us to determine the mean yield across the five sites.

Tasting: In year two, Selman coordinated tastings of high performing varieties at the Vegetable Research Farm summer field day (approx. 70 attendees). Twenty three consumers ranked the sweetness, flavor and texture of six high-performing varieties, each from a different market class. Attendees entered their tasting data into a Seedlinked survey. 

An additional tasting event allowed us to compare irrigated (grown by a local grower) and dry-farmed 'Bella' ananas melon. 

Objective 3: Evaluate the effect of planting density on yield

Year 2 (2023) – We planted a density trial with two replications of four different varieties, planted at three different densities (see the map of the trial). These were managed the same as the OSU vegetable research farm variety trial.

Objective 4: Market and promote dry-farmed melons

Selman promoted dry-farmed melons through a focus group (2022), at a variety showcase, at three field day events, a private event and at the Dry-Farmed Tomato Festival at Wellspent Market. Additional funds were used to work with an artist to develop dry-farmed melon posters and cards. 

Objective 5: Engage other farmers in project outcomes

We engaged with farmers outside of the project team in a number of ways. This included at field days (three), through the dry farmed accelerator program, and the Dry Farming Collaborative Winter Meeting. Additionally, we shared data with Organically Grown Company and the farmer who they are working with to develop their dry farming program. 

Objective 6: Evaluate project outcomes

At the end of the project, we sent a survey to 16 farmers and gardeners that participated in the study. Ten farmers completed the survey. These results are presented in the Education and Outreach section of this report.