Anaerobic Soil Disinfestation Efficacy Against Fusarium oxysporum Is Affected by Soil Temperature, Amendment Type, Rate, and C:N Ratio.

ABSTRACT

A meta-analysis of anaerobic soil disinfestation (ASD) efficacy against Fusarium oxysporum and F. oxysporum f. sp. lycopersici was conducted emphasizing effects of environment and organic amendment characteristics and pot and field studies conducted on ASD amendment CN ratio and soil temperature effects on F. oxysporum f. sp. lycopersici inoculum survival. In a pot study, two organic amendments, dry molasses-based or wheat bran-based, applied at 4 mg of C/g of soil, with 401, 301, 201, and 101 CN ratios, were evaluated against F. oxysporum f. sp. lycopersici at 15 to 25°C. This study was followed by a pot study with temperature regimes of 15 to 25°C and 25 to 35°C and two CN ratios (201 and 401), and a field study at 401, 301, 201, and 101 CN ratios, a 301 CN ratio at a lower C rate (2 mg of C/g of soil), and an anaerobic control. Soil temperature >25°C and more labile amendments increased ASD suppression of F. oxysporum/F. oxysporum f. sp. lycopersici in the meta-analysis. In pot studies, F. oxysporum f. sp. lycopersici survival was reduced for molasses-based mixtures at 201 and 301 CN ratios compared with wheat bran-based mixtures but not compared with the anaerobic control. At 25 to 35°C, all ASD treatments suppressed F. oxysporum f. sp. lycopersici relative to controls. In the field, all ASD treatments reduced F. oxysporum f. sp. lycopersici survival compared with the anaerobic control, and 4 mg of C/g of soil amendment rates induced higher anaerobic conditions and higher F. oxysporum f. sp. lycopersici mortality compared with the 2 mg of C/g of soil rate. Although amendment CN ratios from 10 to 401 were similarly suppressive of F. oxysporum, lower temperatures reduced ASD effectiveness against F. oxysporum/F. oxysporum f. sp. lycopersici and further work is warranted to enhance suppression at soil temperatures <25°C.