Soil Microbial Community Structure Under Different Fumigation Treatments.

For the past few decades, soil fumigants have been extensively used to control target soil borne pathogens, nematodes, weeds and insects. It is known that the fumigants with broad biocidal activity can affect both target and non-target soil organisms, but their effect on microbial community structure are largely unknown until recently. Soil microorganisms are crucial in sustaining health of agricultural soil by contributing to nutrient cycling, soil structure and overall soil quality. Hence, it is very important for them to recover after treatment with fumigants for the development of healthy soils. Two trials were established at a commercial calla lily farm near Moss Landing, CA and at the USDA-ARS San Joaquin Valley Agricultural Sciences Center, Parlier, CA. Phospholipid fatty acid (PLFA) analysis was used to characterize soil microbial community structure under different rates of fumigants; Inline, Pic-Clor 60, Telone C35 and methyl bromide/chloropicrin. The primary objective of this study is to examine and compare the impact of different rates of fumigants on target and non-target soil organisms. Canonical multivariate analysis indicates significant differences in soil microbial community structure between the control and fumigated sites. Canonical analysis suggests that soil microbial communities in the control and low rates of Inline and Telone C35 are similar. Effects of the fumigants on target (Pythium and Fusarium) and non-target organisms (gram positive bacteria, gram negative bacteria, actinomycetes, fungi, arbuscular mycorrhizal fungi and protozoa) will be discussed.