Production and marketing of dry-farmed tomatoes in Oregon

OBJECTIVE: Describe best soil management practices

Soil management trials: The treatment with the highest marketable yield was the low nitrogen fertilizer application treatment and the lowest marketable yield was for the weedy treatment. The dust mulching and gypsum treatments did not differ from the control. High fertilizer nitrogen was associated with high blossom end rot incidence. High compost and leaf mulch treatments resulted in high total fruit numbers, but fruit weight was low and blossom end rot incidence was high. In summary, dry farm tomato soil management recommendations include 1) clean cultivation to control weeds and minimize soil disturbance, and 2)  moderate N fertilization (amendments and fertilizers), as excess N generates high blossom end rot incidence later in the growing season.

Watermark sensor data showed that soil moisture decreased at 6-9 inches and 12-15 inches depth (Table). Sensors at 24-27 inches and 36-39 inches did not detect significant water loss. Soils in the leaf mulch treatment retained more moisture than the other treatments at both 6-9 inches and 12-15 inches. 

Table: Mean soil water potential at two depths on three dates

OBJECTIVE: Identify productive varieties and/or rootstock/scion pairs

Fourteen tomato varieties were identified that are resistant to BER (Table 1). However, these varieties have unacceptably soft fruit when daytime temperatures exceed 95F for several days, and many are susceptible to other physiological disorders including gold top, splitting and cracking, and sunscald. These varieties could be successfully dry-farmed in cooler areas of western Oregon (foothills, coast) or on protected/modified sites (shading, windbreaks, high relative humidity due to nearby overhead irrigation, etc).

High performing rootstock x scion combinations were also identified (Table 2).  Grafting can increase fruit number, fruit weight and reduce BER incidence, thereby increasing marketable yield. However, grafting does not increase fruit firmness in varieties with unacceptably soft fruit when daytime temperatures are high; only genetically firm-fruited varieties should be grown on sites with very high daytime temperatures.

Most rootstocks tested (DRO141TX, Fortamino, Emperador, Maxifort) increased yield and reduced BER incidence to some degree, but Shincheonggang did not.  (Table 3).

Objective:   Evaluate sensory quality and develop recipes

1) identify tomato varieties with good sensory quality

All recommended tomato varieties (above) were determined to have good sensory quality in taste tests.

2) determine if grafting had an effect on sensory quality

In some but not all taste tests, tomatoes grown on grafted plants were considered to have lower sensory quality than tomatoes grown on ungrafted plants.

3) determine if dry farmed tomatoes had more intense flavor than irrigated tomatoes.

Dry-farmed Early Girl tomatoes grown in coastal California are known for their intense flavor, which is accompanied by a relatively small fruit size and 15% average BER incidence (Leap et al., 2017). Because of this dry farm tomato example, many farmers and consumers think that dry farm tomatoes are inherently more intensely flavored than irrigated tomatoes. However, in taste trials of Early Girl and high performing dry farm tomato varieties grown with and without irrigation in western Oregon, consumers described dry farm and irrigated tomatoes as similarly flavorful (data not shown).

Objective: Evaluate profitability of dry farmed tomatoes

Table 6 (Cost and Revenue Analysis) shows the comparative costs associated with growing dry-farmed and irrigated tomatoes. The table uses data from the OSU 2022 and 2023 growing seasons. An important consideration in dry farm tomato production is low marketable yield. Dry farm total yields are lower than irrigated yields, and high incidence of physiological disorders (BER, gold top) further reduce marketable yields. Fortunately, production costs can be lower in dry farm systems. For example, in 2022, dry farm weeding costs were half of irrigated weeding costs, and in dry farm production there are no costs associated with irrigation. Dry farmed tomatoes grown on suitable sites can be profitable.