Thursday, August 9, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
Interactions between plants and soil microbes have been shown to affect plant population and community dynamics. However, there has been relatively little attention focused on understanding the role that plant-soil feedbacks play in mediating crop and weed growth in cropping systems. A greenhouse study was conducted to examine the impacts of soil history, reduction of soil microbial activity, and fertilization on growth of spring wheat, wild oat, and giant ragweed. In the first phase of the study, treatments were established by growing monocultures of each species (and a control in which no species were planted) for 10 weeks. Soils were then subjected to one of four pasteurization/fertilization treatment combinations. Plant-soil feedbacks were assessed in the second phase of the study by growing each species in each of the soil history-treatment combinations. The effects of soil history (identity of the previous species grown in the soil) on wheat and weed biomass varied by species and interacted with fertilizer and pasteurization treatment. In non-pasteurized soil, biomass of spring wheat grown with fertilizer was greatest in soil previously sown with wild oat. In pasteurized soils, biomass of unfertilized spring wheat and wild oat was lowest in soil previously sown with giant ragweed. The range of positive and negative feedbacks generated by our treatment combinations suggests that interactions been weeds, crops, and soil microorganisms are complex. A better understanding of these complex interactions may lead to the development of more effective management strategies.
