Thesis
Soil health and microbial communities in dryland cereal cropping systems of the inland Pacific Northwest
Washington State University
Master of Science (MS), Washington State University
08/2020
DOI:
https://doi.org/10.7273/000004173
Handle:
https://hdl.handle.net/2376/125162
Abstract
Crop rotations influence ecosystem health by creating habitats and symbiotic relationships with soil microbial communities that cycle nutrients, decompose recalcitrant material, and protect the system from stressors. Incorporating new crops into an established system can provide an impetus for a change in soil microbial communities and subsequently soil health. Across three crop rotation studies and one mycorrhizal inoculation study in the low annual precipitation zone (< 300 mm yr-1) of the dryland farming region of eastern Washington, the objectives were to assess the impact of alternative and typical crop rotations on yield, soil microbial community, and soil health. The active microbial community was quantified using phospholipid fatty acid analysis and soil health was measured by assessing soil pH, micro- and macronutrients, and organic matter using the Haney Soil Health Index and Nutrient Tool, PRSTM probes, and conventional analytical methods. A principal component analysis showed that in all three crop rotation studies, soil depth was responsible for a significant clustering effect for all soil properties. Although crop rotations indicated significant influence on microbial communities, rotational differences were not as apparent in any one year as crop entry phase. The typical or "business as usual" 2-year rotation of winter wheat-fallow showed lower total microbial biomass, organic matter, and soil pH than rotations with an additional crop, indicating that incorporation of another rotation crop increases overall soil health. Haney and conventional methods of soil fertility analyses showed strong correlations with each other and similar sensitivity to changes between crop rotations. In the inoculation study, Pearson correlations indicated that conventional and PRSTM probe soil fertility metrics explained the majority of spring wheat yield variation whereas microbial communities were not significantly correlated. Fluctuations within individual microbial family abundance indicated no relationship to overall yields, though within rotations there was a general trend of increased spring wheat yield in inoculated versus control treatments. Our results also showed no yield reductions in spring wheat following winter canola in a rotation of winter canola-spring wheat-fallow, seen in the study region; however, growing winter canola before spring wheat significantly decreased the abundance of arbuscular mycorrhizal fungi in the topsoil.
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Details
- Title
- Soil health and microbial communities in dryland cereal cropping systems of the inland Pacific Northwest
- Creators
- Cassandra J. Rieser
- Contributors
- DAVID RHYS HUGGINS (Advisor) - Washington State University, Crop and Soil Sciences, Department of
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890769001842
- Language
- English
- Resource Type
- Thesis