Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 11/16/2005
Publication Date: 12/12/2005
Citation: Davis, A.S., Anderson, K.I., Hallett, S.G., Renner, K.A. 2005. Weed seed mortality in soils with contrasting agricultural histories [abstract]. North Central Weed Science Society Meeting. 60(1):64. Interpretive Summary:
Technical Abstract: Conservation biocontrol has been proposed as a means of directly reducing weed seedbanks. In this approach, cropping systems are managed to enhance degradation of weed seeds by soil microbes. We examined the relationship between long-term agricultural management practices, soil fungal and bacterial communities, soil C:N ratio, soil particle size fractions, and weed seed mortality. Soil from five fields with over 10 years of contrasting agricultural management histories was used as an incubation medium for seeds of giant foxtail and velvetleaf in controlled environment bioassays. Soil management treatments included a conventional corn-soybean-wheat rotation, an organic corn-soybean-wheat rotation, a conventional corn-corn-soybean-wheat rotation, a reduced-synthetic input corn-corn-soybean-wheat rotation receiving composted manure as a soil amendment, and an early successional system managed with burning and mowing in alternate years. Seed mortality of giant foxtail and velvetleaf were greatest in the conventionally managed systems and lowest in the compost-amended corn-corn-soybean-wheat rotation. The carbon-rich amendment appeared to inhibit microbial attack of weed seeds. There was a strong negative correlation between the first principal component of the 18S region of the fungal ribosome and both giant foxtail (-0.52, P < 0.05) and velvetleaf (-0.57, P < 0.01) seed mortality. The similar strength and direction of these correlations indicate that seeds of the two species were affected similarly by changes in the soil fungal community. None of the other measured soil properties were correlated with weed seed mortality. These results demonstrate that soil management history, fungal community composition and weed seed mortality are linked.