Title: Environmental implications of herbicide resistance: soil biology and ecology Author
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 31, 2013
Publication Date: February 3, 2013
Citation: Kremer, R.J. 2013. Environmental implications of herbicide resistance: soil biology and ecology. Weed Science Society of America Meeting Abstracts. Paper No. 274. Technical Abstract: Soil microbial community structure and activity are clearly linked to plant communities established in natural and agricultural ecosystems. A limited number of studies confirm that weeds alter their soil environment and select for specific microbial communities in the rhizosphere. Such rhizosphere modification is well documented for many crop and horticultural plants. However, the impact of weeds, especially those in agroecosystems, on soil biology and ecology has received less attention because effective weed management practices were developed to minimize the impacts of these plants on crop production. The recent development of herbicide resistance in several economically important weeds leading to unexpected and widespread infestations in crop fields treated with a single herbicide has prompted a re-evaluation of the effects of weed growth on soil biology and ecology. The objective of this paper is to review the potential impacts of herbicide-resistant weeds on soil biological and ecological properties based on previous and on-going studies on crops, weeds and invasive plants. Persistent weed infestations likely establish extensive root systems and release various plant metabolites into soil through root exudation. Many of these exudates are selective for specific soil microbial groups that mediate certain biochemical and nutrient acquisition processes. The exudate chemicals may stimulate development of microbial groups beneficial to weed growth and detrimental to crop growth or beneficial to both crop and weed. Changes in the interactions with symbiotic and associative microorganisms are known, especially for arbuscular mycorrhizal fungi (AMF) that are important in aiding the plant in uptake of nutrients and water, and in protection from soilborne pathogens. Mechanisms used by weeds to potentially disrupt AMF symbioses with adjacent crop plants are not clearly described. However, many herbicide-resistant weeds including Amaranthus and Chenopodium species do not support AMF symbioses and may reduce the density of AMF propagules in soil necessary for establishment of the symbiosis with crop plants in current and subsequent seasons. Impacts of herbicides applied to control herbicide-resistant weeds may compound the effects of weeds on the soil microbial community. Systemic herbicides released through weed roots may select additional microbial groups that mediate detrimental processes such as nutrient immobilization or serve as opportunistic pathogens. An understanding of the complex interactions of weeds with soil microorganisms under extensive and persistent infestations is important in developing effective management systems for controlling herbicide-resistant weeds.