Effect of Biocidal Treatments on Cation Exchange Capacity and Fusarium Blight of Soybean in Delaware Soils

Abstract

Fusarium wilt has caused significant losses in soybean [Glycine max (L.) Merr.] production and is very difficult to control because it is caused by the soil-borne fungus Fusarium oxysporum. A better understanding of the relationship between soil characteristics and the pathogen and between biocidal treatments and physiochemical properties is needed, especially for soils that appear to be suppressive. The effects of autoclaving and Vapam fumigation on cation exchange capacity, organic matter content. clay content, pH, and Fusarium wilt of soybean were determined for several different Delaware soil types (Typic Hapludults, Typic Quartzipsamments, and Typic Umbraqtnults). 'Essex' soybean was grown in the treated soils that had been infested, prior to planting, with 6.3 x 10 4 viable spores per gram of dry soil of a pathogenic Fusarium oxysporum isolate. Treatments were arranged on the greenhouse bench in a randomized completeblock design with five replications. Cation exchange capacity gene•·ally increased with fumigation and decreased with autoclaving, but differences were not significant for all soils. Organic matter content increased following fumigation in three soils, and pH values were lowered by both biocidal treatments in all soils except a Matapeake silt loam. Disease incidence and severity were affected differently for each soil type.Additional index words: Glycine max (L.) Merr., Fusarium oxysporum, Autoclaving, Vapam fumigation, Suppressive soil.

Specific Rhizobacteria Responsible in the Rhizosheath System of Kengyilia hirsuta

“…Autoclaving is known to alter physicochemical characteristics of soil (Mcnamara et al, 2003;Berns et al, 2010;Traoré et al, 2010). Autoclaving is known to increase the soil pH (Jörn et al, 1993), to decrease the cation exchange capacity (CEC), and increasing the electrical conductivity (EC) of soil and N (NH 4 + and NO 3 − ) is not an significant change (Sandler et al, 1988). After collection, the sampled soil was divided into two portions, one of which was sterilized by autoclaving at 121 • C for 1 h. Soil physicochemical characteristics are given in Table 1.…”