|GUO, HAICHAO - University Of Florida|
|ZHAO, XIN - University Of Florida|
|MCNEAR, DAVID - University Of Kentucky|
Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2017
Publication Date: 3/24/2018
Citation: Guo, H., Zhao, X., Rosskopf, E.N., Hong, J.C., Mcnear, D. 2018. Impacts of anaerobic soil disinfestation and chemical fumigation on soil microbial communities in field tomato production system. Applied Soil Ecology. 126:165-173. https://doi.org/10.1016/j.apsoil.2017.12.018.
Interpretive Summary: Anaerobic soil disinfestation (ASD) is a method of treating the soil to manage soilborne plant pathogens without the use of chemical fumigants. This method, using molasses as the carbon source is highly effective, but remains costly for large-acreage application. In an effort to reduce costs, it is essential to have a more in-depth understanding of the mechanisms through which ASD is effective in suppressing the effects of soilborne pathogens. One hypothesis is that significant changes in the microbial community during ASD result in disease-suppressive soil. Determining the groups of bacteria and fungi that dominate the microbial population during and after ASD will provide critical information on mechanism. This work contributes to the potential to reduce the price of the ASD and thus, increase it's use in commercial vegetable production.
Technical Abstract: Anaerobic soil disinfestation (ASD), a potential alternative to chemical fumigation for controlling soilborne pathogens, has been demonstrated in several agricultural production systems. Soil microbial community as affected by ASD is considered one of the major factors responsible for pathogen suppression. However, rather limited information is available, particularly in sandy soils regarding the response of the soil microbial community to ASD throughout the cropping season. A field experiment was conducted to optimize the ASD technique for tomato production in Florida, utilizing two rates of molasses and composted poultry litter (CPL), and a pre-emergent herbicide application. The pre-plant soil treatments included ASD with 6.93 m3 ha-1 of molasses and 11 Mg ha-1 of CPL (ASD0.5), ASD with 13.86 m3 ha-1 of molasses and 22 Mg ha-1 of CPL (ASD1.0), and chemical soil fumigation control (CSF). The herbicide treatments included halosulfuron application and without halosulfuron application control. Soil microbial community composition was monitored using phospholipid fatty acid (PLFA) analysis during the fall 2015 tomato production season. Halosulfuron application did not result in changes in the soil microbial community during the season. CSF led to significantly lower levels of bulk soil total microbial biomass, Gram negative bacteria, Gram positive bacteria and actinomycetes, in contrast to the ASD treatments. However, the rhizosphere effect of plants under CSF alleviated the stress and stimulated the growth of Gram negative bacteria and protozoa to reach similar levels to that of rhizosphere soils under the ASD treatments. Gram positive bacteria in bulk soils under the three soil treatments significantly decreased while the fungi:bacteria ratio in bulk soils under CSF significantly increased, from 0 to 36 days after transplanting (DAT), and then remained stable throughout the season. Despite the similar microbial composition in bulk and rhizosphere soils between the two ASD treatments, the dynamic changes of some biomarker groups in bulk soils from 0 to 99 DAT showed distinct patterns particularly for total microbial biomass, Gram negative bacteria, actinomycetes, and fungi. Bulk soil microbial community composition was shifted after 36 DAT under all soil treatments, and remained stable until the end of season. The changes in soil microbial community composition over time were related to soil nutrient changes. This study suggested that the stability of soil microbial communities after 36 DAT under ASD treatments may play an important role in suppression of soilborne pathogens.