Evaluating Management Practices for Controlling Blossom-end Rot and Other Blemishes in Dry-farmed Tomato

Dry-farmed tomato ( Solanum lycopersicum ) is emerging as a popular crop along the west coast of the United States. A number of blemishes of the fruit, including blossom-end rot (BER), yellow shoulders, sunscald, and splitting and cracking, can diminish marketable yields for dry-farmed tomato. Growers want to produce intensely flavored dry-farmed tomatoes while preventing blemishes like BER. Two trials were conducted during the 2023 growing season to test methods for controlling BER in dry-farmed tomato. The first trial was conducted at a university research farm and tested five different treatments, including sheltering the tomato plants from the wind by intercropping with maize ( Zea mays ), no organic fertilizer, reduced application (50 lb/acre nitrogen) of organic fertilizer, tighter in-row spacing, and trellising, against a control. The second trial was a fertilizer trial with three treatments; organic fertilizer was applied at 0, 50, and 100 lb/acre nitrogen, and it was conducted at the research farm and five commercial farms. Reducing the amount of fertilizer applied decreased BER, but it also increased the average fruit size, decreased fruit soluble solids concentrations (SSCs), and increased the incidence of yellow shoulder. Additionally, on a site with an exceptionally low soil pH and phosphorus concentration, fertilizer applications increased total and unblemished yields. Other treatments tested at the research farm, including intercropping with maize, decreasing in-row spacing, and trellising, did not affect BER incidence. However, the research farm trial had very little BER (BER incidence of plots, 0%–7%), especially compared with that in on-farm trials (BER incidence, 0%–87%). Trellising increased unblemished yields and average fruit weights. Both trellising and decreasing in-row spacing reduced sunscald incidence, likely because of increased foliar coverage of the fruit. Sites differed considerably in yield, BER incidence, and fruit SSC. The results suggest that dry-farmed tomato flavor intensity is affected by site properties (i.e., “terroir”), and factors that increase drought stress may also increase fruit SSC. This presents a conundrum for growers because methods that control BER and increase unblemished yields may decrease tomato flavor intensity.