|MARGHERITA, ZAVATTA - University Of California|
|SHENNAN, CAROL - University Of California|
|MURAMOTO, JOJI - University Of California|
Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 10/11/2014
Publication Date: 11/9/2014
Citation: Margherita, Z., Shennan, C., Muramoto, J., Mazzola, M. 2014. Evaluating C-sources for anaerobic soil disinfestation. International Conference on Methyl Bromide Alternatives and Emissions Reductions. 12.1-12.4.
Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge in strawberry production systems when re-planting in fields previously planted to strawberry. Modifications to existing regulations are likely to intensify this challenge by further limiting availability of fumigants, increasing the cost of application, and limiting total orchard use due to buffer zone restrictions. Anaerobic soil disinfestation (ASD) was developed in Japan and the Netherlands as an alternative to soil fumigation and involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. Disease control is believed to result from the production of certain volatiles that are generated by microorganisms that are active under anaerobic conditions. Results from this study demonstrate that the effectiveness of ASD in the control of soil-borne pathogens will be determined, in part, by the type of carbon amendment that is used in application of the ASD process. Different carbon inputs used in this study produced differential effects on the resident soil microbial community. Those carbon sources that induced distinct shifts in the soil fungal community during ASD also resulted in significant increases in strawberry yields. Conversely, those carbon sources that failed to shift the soil fungal community during ASD also failed to enhance strawberry yields. These findings demonstrate the importance of carbon input when formulating the implementation of ASD for control of soil-borne plant diseases.
Technical Abstract: Anaerobic soil disinfestation (ASD) has been shown to be effective in the control of a wide range of soil-borne plant pathogens. Efficacy of ASD was previously shown to be influenced by carbon input utilized when applied to apple orchard systems. In strawberry, ASD provided comparable yield as that attained with fumigants in coastal CA when rice bran (RB) at 9 t/ac was used as a C-source. . However, applying 9 t/ac of RB may release excess nitrogen to the environment and the increasing cost of RB may limit further adoption of ASD. In addition, the capacity to generate biologically effective microbial communities and fungicidal volatiles during the ASD process has been shown to vary in a carbon input-dependent manner. A range of C-sources and rates were tested in field trials. ASD treatments using RB 6 and 9 t/ac and RB in combination with Molasses (Mol) resulted in the best yield, which were equivalent to fumigation with PicClor-60 and higher than fumigation with methylbromide/chloropicrin. Similar results were obtained with or without pre-plant fertilization. Grape pomace appears to be another good candidate as a carbon source for ASD but based upon yield data, pre-plant fertilization will be necessary. Molecular analysis of soil microbial communities demonstrated distinct shifts in community composition in response to treatments. Notably the fungal communities in the ASD conducted with Mol treatments were unchanged relative to the control, and failed to enhance yields. All carbon sources that induced microbial shifts during ASD provided enhanced strawberry yields. The enhanced yields corresponding with the observed shifts in microbial community structure suggest that these changes may contribute to overall plant performance and further demonstrate the importance of carbon input when formulating the use of ASD for soil-borne disease management.