2018 ASHS Annual Conference

The main approach of anaerobic soil disinfestation (ASD) in Florida, a method for pre-plant soil treatment, consists of combining the application of the molasses (C source) with the application of composted poultry litter (CPL) as an organic amendment. However, CPL is not always available locally and is rich in phosphorous. Conventional growers are reluctant to use CPL to avoid any potential food safety issue. In this study, alternative organic amendments, such as composted yard waste (CYW) which poses no food safety issue and is inexpensive and available locally, was used as a substitute for CPL. The main purpose was to evaluate the economic profitability of treatments using alternative organic amendments. Two open-field tomato production trials were conducted at two research stations during the fall 2016 season in Immokalee and Citra, FL. Different application rates of alternative organic amendments (e.g., CYW) were compared to chemical soil fumigation (CSF) as a control. Economic profitability analysis of all eight soil treatment methods was conducted. The results showed that ASD treatment with CPL 11 Mg ha^-1 and molasses 7 m³ ha^-1 achieved the highest gross return among all treatments tested. Compared with CSF, most of the relative net returns of ASD treatments with CYW were negative. ASD treatments with CYW had lower land preparation cost than ASD with CPL, but the marketable tomato yields were lower. The relative net return of all ASD treatments with CYW compared with CSF decreased with tomato prices but increased with tomato yield. The breakeven molasses prices for ASD treatment with CPL to be comparable with CSF were lower than the current agronomic molasses market price ($6/gallon). Higher price of tomatoes gave higher breakeven molasses price. At the current high cost of using molasses as the carbon source, ASD treatments cannot surpass CSF in economic profitability. Alternative carbon inputs that reduce pre-treatment costs while maintaining the high tomato yield achieved using ASD are needed in order to increase the adoption rate of this promising non-chemical soil disinfestation practice.