Effects of Anaerobic Soil Disinfestation and Herbicide Application on Tomato Production and Fruit Quality

Anaerobic soil disinfestation (ASD) is a potential alternative to chemical dependent fumigation for controlling soilborne pests. The promising effect of ASD has been demonstrated in the U.S. recently, but more studies are needed to optimize site-specific application of ASD in tomato production. A field study was conducted to evaluate the response of tomato production and fruit quality to ASD with different rates of carbon and nitrogen sources and use of preemergent herbicide. The field experiment was carried out in Citra, FL during August to December 2015 using a split plot design with four replications. The pre-plant soil treatment was the whole plot factor, and herbicide treatment was the subplot factor. The pre-plant soil treatments included ASD with 6.93 m³ ha^-1 of molasses and 11 Mg ha^-1 of composted poultry manure (ASD0.5), ASD with 13.86 m³ ha^-1 of molasses and 22 Mg ha^-1 of composted poultry manure (ASD1.0), and chemical soil fumigation control with Pic-Clor 60 at a rate of 224 kg ha^-1 (CSF). The herbicide treatments included Sandea application at a rate of 70 g ha^-1, and no Sandea application control. Determinate tomato ‘Tribute’ was transplanted 3 weeks after the treatment. Destructive sampling at the second fruit harvest showed that both ASD treatments resulted in significantly higher biomass allocation to stem, and significantly lower biomass allocation to fruit compared with CSF. Significantly higher potassium concentration and lower sodium concentration were also observed in leaf, stem and fruit under ASD treatments in contrast to CSF. ASD treatments did not differ significantly from CSF in total and marketable fruit number and weight, while ASD0.5 led to significantly higher number and weight of extra-large size fruit compared with CSF and ASD1.0. Significantly higher number and weight of cull fruit were observed under ASD1.0 treatment in contrast to CSF and ASD0.5. Sandea application had no effect on total or marketable fruit number and weight. Tomato fruit of the ASD treatments had significantly higher titratable acidity and lower sugar/acid ratio compared with CSF, while Sandea had no effect on fruit quality measurements including color, firmness, pH, soluble solids content, titratable acidity, and sugar/acid ratio. ASD treatments showed no difference from CSF on weed control, but Sandea significantly suppressed the growth of nutsedge both on plastic and in planting holes. Considering to reduce costs of ASD, ASD0.5 with lower composted poultry manure and molasses application rates may be a better option than ASD1.0 for CSF alternative.