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United States Department of Agriculture

Agricultural Research Service

Research Project: Alternatives to Methyl Bromide for Vegetable and Floriculture Production

Location: Subtropical Plant Pathology Research

Title: Comparison of anaerobic soil disinfestation and drip-applied organic acids for raised-bed specialty crop production in Florida

Authors
item Rosskopf, Erin
item Burelle, Nancy
item Hong, Jason
item Butler, D -
item Noling, J -
item He, Z -
item Booker, B -
item Sances, F -

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2014
Publication Date: N/A

Interpretive Summary: Anaerobic soil disinfestation (ASD) is a soil treatment method that has been studied in multiple countries for the suppression of plant pathogenic fungi and bacteria. The approach is to incorporate soil organic amendments, cover the soil with clear plastic, and saturate the soil with irrigation water. Recent work in the U.S. has included studies on weed control and nematode management with this technique. Multiple mechanisms have been shown to play a role in the suppression of some studied plant pathogens, including the generation of organic acids by soil bacteria. Multiple field trials were conducted in the strawberry production region in Florida to compare this method with direct application of a novel combination of organic acids (referred to as ‘SPK’) applied through drip irrigation. Application of the organic acids consistently resulted in an increase in the native soil population of Trichoderma spp. which are often considered to be beneficial fungi. The first year of ASD treatment resulted in a low level of anaerobic conditions and an increase in Trichoderma spp. However, in the second year, when there was a higher level of anaerobicity, an increase in culturable soil bacteria overwhelmed Trichoderma spp. colony isolation. Viability of introduced fungal plant pathogen inoculum was reduced in organic acid treatments when the water front carrying the acid came in direct contact with packets at the center of the bed, but not in areas with poor material movement. Introduced inoculum in the ASD-treated plots was significantly reduced compared to the untreated control regardless of packet location.

Technical Abstract: Anaerobic soil disinfestation (ASD, aka biological soil disinfestation) has been studied in multiple countries for the suppression of plant pathogenic fungi and bacteria. Recent work in the U.S. has included studies on weed control and nematode management with this technique. Multiple mechanisms have been shown to play a role in the suppression of some studied plant pathogens, including the generation of organic acids by soil bacteria. Multiple field trials were conducted in the strawberry production region in Florida to compare this method with direct application of a novel combination of organic acids (referred to as ‘SPK’) applied through drip irrigation. Application of the organic acids consistently resulted in an increase in the native soil population of Trichoderma spp. The first year of ASD treatment resulted in a low level of cumulative redox potential and an increase in Trichoderma spp. However, in the second year, when there was a higher level of cumulative redox potential, an increase in culturable soil bacteria overwhelmed Trichoderma spp. colony isolation. Viability of introduced fungal plant pathogen inoculum was reduced in organic acid treatments when the water front carrying the acid came in direct contact with packets at the center of the bed, but not in areas with poor material movement. Introduced inoculum in the ASD-treated plots was significantly reduced compared to the untreated control regardless of packet placement. ASD, when crop nutrition was monitored and adjusted accordingly, resulted in a significant increase in yield when compared to organic acid application and the untreated control.

Last Modified: 8/19/2014
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