Floor Management and Amendment Applications Affected Dry-farmed Tomato Production during a 2020 Experiment in the Willamette Valley of Oregon

‘Early Girl’ tomato ( Solanum lycopersicum ) was dry-farmed during 2020 to determine the effects of floor management and amendment treatments on the total and unblemished yields, average fruit weight, blossom-end rot (BER) incidence, sunscald incidence, plant size, soil water tension, predawn leaf water potential (PDLWP), and leaf and soil nutrient concentrations. Floor management treatments included leaf mulching (4 inches of semi-composted leaf mulch), dust mulching (mechanical tillage to a depth of 6 to 8 inches after rain events), and a weedy treatment (weeds were not controlled). Amendment treatments included high compost (additional 73.5 wet tons/acre), high nitrogen (N) (160 lb/acre N applied as composted chicken manure and feather meal), low N (40 lb/acre N), and gypsum (2075 lb/acre gypsum). All these treatments were compared with a clean-cultivated control fertilized at 100 lb/acre N. No floor management treatment performed better (referring to total yield, unblemished yield, fruit count, fruit weight, BER incidence, sunscald incidence, and PDLWP) than the clean-cultivated control, and the leaf mulch and weedy treatments performed significantly worse. The leaf mulch treatment decreased the average fruit weight (30%), increased the BER incidence (34%), and increased the necrotic BER incidence (88%) when compared with the control. However, the leaf mulch treatment also used soil moisture more slowly than the control did. The weedy treatment decreased total yields (65%) and unblemished yields (88%), decreased the total fruit count (53%), decreased the average fruit weight (25%), increased the BER incidence (53%) and necrotic BER incidence (82%), decreased PDLWP (suggesting that the plants were more drought-stressed) on 20 Jul (27%) and 3 Aug (44%), and resulted in smaller plants when compared with those treated with the control. No amendment treatment performed better than the control, and the high compost treatment performed significantly worse. When compared with the control, the high compost treatment decreased the average fruit weight (15%), increased the BER incidence (39%), increased the necrotic BER incidence (67%), and increased plant aboveground biomass at the end of the experiment (34%). Increasing applications of organic fertilizers increased the BER incidence, with 48% BER at 40 lb/acre N and 62% BER at 160 lb/acre N. These data suggest that excess fertilizer applications and factors that increase drought stress (e.g., weeds) induce BER in dry-farmed tomato. Dust mulching may not be necessary, and shallow cultivation can be used instead for weed management. Dry farmers in the Willamette Valley must control weeds and avoid excess soil fertility and leaf mulches because they can result in large plants with a large fruit set; however, these fruit are more susceptible to BER.