Date of Graduation

2016

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

James A Thompson

Committee Co-Chair

Trevor M Harris

Committee Member

Louis M McDonald

Committee Member

Edward B Rayburn

Committee Member

Jeffrey G Skousen

Abstract

This study was conceived to investigate the fate of organic P (Po) in typical hay and grass pasture of eastern West Virginia. It is not uncommon in this region of West Virginia for hay and grass pastures to receive annual applications of animal manure, often on a nitrogen basis. As P management has evolved, many farms in the region have begun to use management tools such as a P index to continue use of animal manure as N fertilizer. However, many hay and grass pastures in the region already have a high degree of P saturation. There are reasonable expectations that in time the P saturation at these sites may reach thresholds whereby actions to lower P saturation become necessary. At such time it may become necessary to develop interception strategies to prevent movement of P into surface and ground water from there extremely saturated locations. While most P research focuses on P loss via surface erosion, or on tile drained land, and rarely is Po considered. To fully evaluate the risks of P loss and develop remediation and interception strategies, data specific to Po movement at field scales across complex landscapes is needed to increase assurances that existing research is compatible with or applicable to West Virginia pastures. To develop this data, sequentially extracted P fractions were measured in samples from both spatially-explicit locations across typical hay and grass pastures and from bench top experiments to evaluate the applicability of existing research. I examined patterns in Po distributions to determine if Po levels significantly exceeded what could be explained by changes in soil properties. Results support the presence of spatial structure in the variability of the NaHCO3 and HCl extractable Po fractions in some locations, but no purely spatial component is present in the variability of the NaOH and H2O extractable fractions. Various topographic parameters were evaluated to determine their efficacy in explaining Po variability and soil-landscape modeling techniques were successfully used to develop relatively simple models based on soil test P results and topographic data to predict the distributions of the sequential extracted Po fractions across these landscapes. The bench top experiment indicated no significant effects from actively growing plants or P sources on the disposition of Po. As such, the bench top results support the acceptance of existing data in decision making processes, and the field scale data supports development of soil landscape models to afford future environment professional a higher degree of understanding relative to the spatial distribution of sequentially extracted Po fractions at a landscape scale.

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