Thesis
Direct-seed induced soil chemical stratification and surface applied lime effects on soil microbial community composition, aluminum solubility and mobility, and crop biomass
Washington State University
Master of Science (MS), Washington State University
2016
Handle:
https://hdl.handle.net/2376/101611
Abstract
Soil pH controls most soil processes including: mineral dissolution, metal availability, microbial community structure, and fertility. The Palouse farming region located in the Pacific Northwest has been experiencing decreasing soil pH and the issues that accompany acidified soils. This region has a large number of farmers that employ no-till systems to reduce topsoil loss. However, these no-till systems increase soil stratification due to reduced mechanical mixing of soils. Aluminum (Al) becomes more bioavailable at lower pH values and Al phytotoxicity has become an emerging problem, reducing yields throughout the region. Also soil acidification is a relatively new issue in the Palouse, and there is little known about Al thresholds and how extraction types link to yield losses. While liming may be a viable option to increase pH and reduce aluminum concentrations, no-till systems fail to incorporate lime into the soil. It is known that soil depth and chemistry affect soil microbe community structure however, little is known about how no-till systems affect microbial community composition directly. Thus, objectives of this study were to (1) confirm and characterize chemical stratification in DS systems at a highly resolved spatial scale (2-cm increments), (2) characterize soil microbial community compositional responses to stratification, (3) determine how DS stratification and microbial community at depth respond to surface application of lime, and (4) determine what measurement of Al is the best indicator for crop yield loss. To meet these objectives, soils were sampled at 2-cm increments, at two different Palouse agricultural sites and analyzed 6-months and 18-months after two types of lime were surface applied. Significant differences were apparent at each depth in almost all measured soil chemical variables and surface application of lime was effective at increasing soil pH and decreasing available Al, 18-months after application. Soil microbial community responded to the soil pH and Al gradient with depth, most clearly within the bacterial community at both sites. Water extractable-Al also was highly correlated with crop biomass and considered the best measurement of Al phytotoxicity in Palouse soils. The 2-cm sampling increments proved key for capturing soil chemical stratification and subsequent microbial community shifts.
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Details
- Title
- Direct-seed induced soil chemical stratification and surface applied lime effects on soil microbial community composition, aluminum solubility and mobility, and crop biomass
- Creators
- Victoria P. Barth
- Contributors
- Tarah S. Sullivan (Degree Supervisor)
- 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; [Pullman, Washington] :
- Identifiers
- 99900525086501842
- Language
- English
- Resource Type
- Thesis