Soil microbial communities and grain quality as affected by spring wheat (Triticum aestivum L.) cultivar and grain mixtures in organic and conventional management systems

• Author / Creator

  Nelson, Alison Gail

• It may be possible to tailor crop management to encourage diverse soil microbial communities and beneficial microorganisms, and produce high quality food products. Studies were carried out in 2005-2007 to evaluate the impact of spring wheat (Triticum aestivum L.) cultivar choice and crop polycultures on soil microbial communities in organic and conventional systems, and subsequent wheat quality. Five wheat cultivars were grown organically and conventionally to evaluate grain breadmaking quality and micronutrient content and their impact on the soil microbial community. Organic grain yields were roughly half of conventional yields, but quality levels were all acceptable for Canadian Western Hard Red Spring wheat. Measured soil (0-15 cm) microbial profiles (by phospholipid fatty acid analysis) differed between the two management systems, and amongst cultivars in the conventional system. The most recent cultivar in the study, AC Superb, exhibited the highest levels of fungi suggesting that breeding efforts in conventionally managed environments may have resulted in cultivating mycorrhizal dependence in that environment. In general, many of the studied grain micronutrients were greater in the organically grown wheat system, possibly due in part to decreased grain yield and smaller grain size. Maximizing grain micronutrient content through wheat cultivar choice was dependent on management system. The presence of fungi biomarkers appears to have improved uptake of Mn and Cu. Monocultures and polycultures of common annual crops were grown organically and conventionally in 2006-2007. Intercrops exhibited an ability to overyield in an organic system, largely through weed suppression, but intercrops also overyielded in a conventional system where weeds were controlled through herbicides. As intercrop complexity decreased, the instances of improved weed suppression declined. Management systems and wheat cultivars can alter the composition of the soil microbial community. Annual crop polycultures did not alter soil microbial communities in this study, but showed evidence of agronomic benefits in both organic and conventional systems.

• Subjects / Keywords

  • Soil microbial community
  • Arbuscular mycorrhizal fungi
  • Organic agriculture
  • Grain quality

• Graduation date

  Fall 2011

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3VM4B

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.