Location: Water Management ResearchTitle: Recovery of soil microbial communities after fumigation with time) Author
|Gerik, James - Jim|
Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 5/12/2014
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: In the past few decades, soil fumigants have been extensively used to control target soil borne pathogens and weeds for high value cash crops. However, the fumigants with broad biocidal activity can affect both target and non-target or beneficial microorganisms in soil, but the recovery of soil microbial communities after fumigation is unknown until recently. It is important to study the recovery of soil microbial communities after fumigation because soil microorganisms play an important role in sustaining health of agricultural soil by contributing to nutrient cycling, soil structure and overall soil quality. The present study evaluated the post fumigation recovery of soil microbial communities overtime and the study captured both short-term and long-term changes in microbial communities after continuous fumigation with different fumigants. The main objective of this study is to determine the recovery of soil microbial community structure after continuous fumigation with different time frames. The study was conducted in the Watsonville area, the dominant strawberry growing region of California, USA. Chronosequences were chosen considering Jenny’s state factors (1941): organisms, climate, relief, parent material and time; sites were chosen which were as similar as possible. The chronosequence selected for this study contained four sites defined by number of years since fumigation (ysf) with methyl bromide. The sites were a 15 year old site at the time of sampling, a 33 year old site, a 39 year old site, and an organic farm. Soil samples were collected in May 2013 from 0-5, 5-15 and 15-30 cm depths. Three 100 m transects serving as replicates were randomly placed on research sites and soil samples were collected from three equally spaced points along each transects. Phospholipid fatty acid analysis and terminal restriction fragment length polymorphism were used to characterize recovery of soil microbial community structure after fumigation. Our results indicate disparities in soil microbial contents at different fumigated sites and non-fumigated sites, indicating differences in microbial biomass production. For the 0-5, 5-15 and 15-30 cm depths, all bacterial, mycorrhizal and actinomycetes groups were significantly greater in non-fumigated and organic sites as compared to methyl bromide fumigation sites. Mechanisms responsible for these differences will be discussed.