2019 ASHS Annual Conference

Proposed as a biological strategy for control of soilborne pests and pathogens, anaerobic soil disinfestation (ASD) is implemented by amending the soil with an easily-decomposable source of carbon (C) and other organic amendments combined with water soil saturation and polyethylene mulching. The ASD method developed in Florida relies primarily on the combined use of molasses (M) as the C source and composted poultry litter (CPL) as a supplementary organic amendment. While this approach is effective, the use of CPL poses a series of issues related to the high content of phosphorus (P), food safety, and limited availability. A study was conducted to investigate the potential of composted yard waste (CYW) as a substitute for CPL and to test Soil Symphony Amendment (SSA,) a commercial biological soil management strategy, in comparison with ASD, chemical soil fumigation (CSF), and an untreated check. Eight alternative soil management strategies were evaluated for their effects on soil nutrient availability, plant growth, nutrient accumulation, and yield in a fresh-market tomato crop during the fall 2016 season in Immokalee, FL. ASD applied using 6.93 m³ ha⁻¹ of M and 11 Mg ha⁻¹ of CPL (ASD0.5) led to the highest availability of K, P, Mg, and Na throughout the growing season and a higher availability of S toward the end of the growing season. Substituting CPL with CYW at the rate of 26.9 Mg ha⁻¹ (CYW1+M) or 13.45 Mg ha⁻¹ (CYW0.5+M) provided lower but still adequate levels of macronutrients compared to ASD0.5. ASD0.5 resulted in the lowest soil NO₃-N content during the first 14 days of treatment. Limited and inconsistent differences were observed between soil treatments regarding soil micronutrient content. At 30 and 60 days after planting (DAP), ASD0.5 plants had the highest total plant biomass. At 60 DAP similar levels of biomass were produced by CYW0.5+M and CSF plants, while a slightly lower plant biomass resulted from CYW1+M. The higher plant biomass and availability of nutrients observed in ASD0.5, CYW0.5+M, CSF, and CYW1+M also resulted in a higher accumulation of nutrients in the plant tissues as compared to the other treatments. Marketable fruit yield was highest from ASD0.5 plants, but CSF, CYW1+M, and CYW0.5+M plants provided similar yields. It is concluded that, substituting CPL with CYW may reduce the risks of nutrient loss, especially for P, during the ASD treatments without reducing plant growth and yield.