First Advisor

William Fish

Term of Graduation

Spring 2009

Date of Publication

5-4-2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.) in Environmental Sciences and Resources

Department

Environmental Sciences and Resources

Language

English

Subjects

Soils -- Cadmium content -- Oregon, Organic farming -- Research -- Oregon, Fertilizers -- Research -- Oregon

DOI

10.15760/etd.8012

Physical Description

1 online resource (2, xvi, 149 pages)

Abstract

Organic farming has become a multimillion dollar industry and while much emphasis is put on subsequent fertilizer inputs onto these fields, very little consideration is given to the prior fertilization activities of these soils. For a farm to be certified organic it means no harmful chemicals have been applied for at least three years.

The overall hypothesis tested by this research was that equilibrium adsorption models can adequately represent the behavior of fertilizer-derived cadmium in Oregon agricultural soils and that such model results can be easily incorporated into risk assessment models, transport study models and persistence studies for organic or other sustainable farming considerations. Soil chemistry and soil characterization were used to calculate the doubling time and mass flux of cadmium-derived fertilizer in loamy and sandy agricultural soils with a rich farming history. We also investigated the processes controlling the release of fertilizer-derived cadmium in the micro scale zone around the fertilizer to determine if a local equilibrium model was appropriate for explaining cadmium behavior in agricultural soils.

The Kd values and adsorption trend of the soil sites was Pendleton > Klamath > Hyslop > Hermiston. The cadmium Kd values were most correlated to the pH of the soils (R2=0.94). The buffer capacity of the soils was highly correlated to the clay content (R2 = 0.98). The adsorption coefficients were important for predicting the doubling times of cadmium in the soils (Hermiston, 4.8yrs > Hyslop, 3.7yrs > Klamath, 2.9 yrs> Pendleton 2.3 yrs). Precipitation was not the most important parameter in predicting the mass loss due to leaching after three years (46.2, 19.9, 16.7 and 8.3 mg/ha-yr for Hyslop, Hermiston, Pendleton and Klamath respectively). The period was found to have a negligible effect on the background concentrations of cadmium in agricultural soils.

Scanning electron microscopy, X-ray diffraction and column displacement experiments were used to investigate the fertilizer kinetics of fertilizer-derived cadmium and the processes controlling the release of fertilizer-derived cadmium were found to be a Cd-phosphate phase, possibly cadmium hydroxyapaptite, and iron oxides. The release of Cd from phosphate fertilizer was slow so a local equilibrium model was appropriate for agricultural soils.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/

This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Comments

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL.

Persistent Identifier

https://archives.pdx.edu/ds/psu/38623

Download

Share

COinS