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 °Brix than fully irrigated melons. In addition, deficit irrigation in some years reduced fruit firmness. In a Turkish study (Akhoundnejad and Dasgan 2019) of 9 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 fruit °Brix when dry farmed than when grown with full irrigation. For other varieties, yield and °Brix were lower when dry farmed. 

Flavor: The Dry Farm Collaborative, led by Garrett, conducted a melon demonstration in 2019 in which they compared the flavor of dry farmed and irrigated melons with a focus on  varieties considered to be high performing when dry farmed. Consumer taste tests of these melons indicate that dry-farming can increase melon 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 (Cresell 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 15 sq ft per plant spacing was most productive, as blossom end rot incidence (which renders fruit unmarketable) decreased and fruit number increased as density increased.

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: 4 OP, 1 F1; five muskmelons: 3 OP, 2 F1; two honeydews: 1 OP, 1 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, 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 farm 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-farm 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 farm melons:
Grafting of melons has been widely shown to reduce soilborne 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 soilborne disease management; they tried grafting melons, but were unsuccessful.

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-farm 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 8 of the farmers in this project are also 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 will work with Stone and FRA to identify cultivars to include in the 2022 variety trial. They will participate in the project farmer field day to evaluate/identify promising cultivars, and a winter project planning and evaluation zoom meeting.

Year 2 (2023)

Farmers will participate in a winter 2022-23 zoom meeting and work with Stone to identify cultivars to include in the 2023 variety trial. They will host on-farm cultivar trials, participate in the project farmer field day to identify and describe promising cultivars, present at project presentations and workshops, and participate in a final winter project evaluation zoom meeting.

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, the project will evaluate only the grafted scion/rootstock combinations (rootstock ‘Shintoza’) currently 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 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 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 germination 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 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 foot between row spacing is about as wide as you can go and still lay a layer of 12’ 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.

Handling and Storage – After harvest, melons should be moved to a cool, dark location to finish ripening. They should only be moved into the cooler once they are completely ripe, as moving them into a cooler will arrest the ripening process. This is especially true for inodorus melons and watermelons. Refrigerating melons for too long can affect their texture.

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: Approximately 100 cultivars (2022 high performing cultivars and grafted plants, plus new cultivars) will be grown by Stone/FRA at the OSU research station, with harvest frequency and measurements as in 2022.

On-farm trials: Project farmers, with Stone and FRA assistance, will conduct 10 on-farm trials in year two.  Before or at planting, project staff will collect 5 ft soil borings from each site and Andy Gallagher, soil scientist, will describe the profile and quantify its available water holding capacity, the most important predictor of the site’s dry farm suitability and productivity.  Watermark sensors will be installed in the melon plots at 2 and 4 ft depths to assess the relative speed and depth of soil drying of the sites.

Approximately six of the 2022 high performing grafted or ungrafted cultivars (2 varieties of each of the 3 melon types) will be selected by farmer partners for inclusion in 2023 on-farm trials. All farms will grow 5-8 plants of each cultivar at 15 sq ft per plant, with effective border rows. For the 5 farms located near OSU, OSU staff will collect harvest data. Harvest frequency and measurements taken will be the same as for the research station experiments.

Research station and on-farm data will be collected and interpreted using mixed effect modeling with cultivar as the fixed effect and farm as the random effect.

To capture farmer preferences related to cultivar qualities other than yield (e.g. days to maturity, size, type, appearance, taste, smell), and to capture information on all 10 on-farm trials, all farmers will rank and describe positive and negative qualities of the cultivars grown on their farms using provided ballots. In addition, farmers will taste, rank and describe the top 5 varieties of each of the three melon types at the project farmer field days.

Yield/quality, rank, preference indices, tasting results, and descriptive information will be summarized and discussed in winter meetings with farmers to identify the overall top performers.

Tasting: In year two, as in summer 2021 for dry farm tomatoes, Selman will coordinate take-home tastings of high performing varieties or scion/rootstock combinations at the Dry Farm Collaborative summer field day (approx. 150 attendees) and winter meeting (approx. 120 attendees). The goal will be to have at least 40 consumers rank the sweetness, flavor and texture of the 3-5 highest performing varieties of each of the three melon types. Attendees will volunteer to participate in the tasting, and each will decide to taste 1 set, 2 sets or all 3 sets (watermelon/muskmelon/honeydew). Each volunteer will be given 1-3 bags, each containing 3-5 samples, a tasting ballot, and a dry farm melon sticker as a thank you gift.  Volunteers will take the bags home, taste the melons within 4 hours, and enter their tasting data into an online Qualtrics survey. Ballots will ask tasters to rank samples for sweetness, flavor attributes, texture, appearance and overall liking. Data will be analyzed using mixed effect modeling with cultivar as the fixed effect and participant and date as the random effects.

Partner farmer field day:
A second partner farmer field day will be conducted by Stone and FRA in August 2023, using the 2022 methods.

Objective 3: Evaluate the effect of planting density on yield

Year 2 (2023)
Three top-performing cultivars or scion/rootstock combinations (from variety evaluations year 1) will selected for planting density evaluations conducted by Stone and FRA at the OSU vegetable research farm in year 2. Each cultivar will be grown at 6 densities (10-60 sq ft per plant, 7 plants per plot) arranged in the field as a density gradient. Guard rows will separate and surround the cultivar-specific density experiments. Measurements taken will be the same as for the research station experiments. Data will be analyzed by ANOVA/mean separation and linear regression.  This split plot design will be tested using mixed effects modeling with the effect of density nested within cultivar.