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Author ORCID Identifier


Campus-Only Access for Five (5) Years

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Environmental Conservation

Year Degree Awarded


Month Degree Awarded


First Advisor

Allen V. Barker

Second Advisor

Masoud Hashemi

Third Advisor

Wesley Autio

Fourth Advisor

Timothy Randhir

Subject Categories



Farmers rely on fertilizers of all types to feed the growing population of the World. Organic fertilizers are naturally occurring materials of biological or mineral origin and are low in nutrient concentration or solubility or have both properties, unlike chemical fertilizers that generally have high solubility and rapid availability. Consumer demand for organically grown crops and mounting interest in organic greenhouse production are rising. Challenges with the use of organic fertilizers include differences in the concentration of nutrients, the speed of their release, and the synchrony between N mineralization and crop N demand. Organic fertilizers and urea were equally effective in supporting growth and affecting nutrient accumulation in lettuce if sufficient N was supplied. We studied yields, nitrogen metrics, and the quality of the lettuce in response to the fertilization of harvested lettuce. The result revealed that increasing nitrogen application rates result in a significant increase in fresh biomass of lettuce. We further obtained lettuce spectral reflectance to estimate the chlorophyll and nitrogen content of the produce. A workflow was further developed to approximate lettuce fresh biomass from the images taken by Micasense red edge. Furthermore, we evaluated the long-term effects of hardwood charcoal (biochar) on the fertility of soil and biomass of the plant. The objectives of this field study were to evaluate the long-term effect of sugar maple hardwood charcoal (biochar) as a soil amendment. The design of the experiment was repeated over two growing seasons with edible soybean (edamame; Glycine max Merr.) production. Main plots were allocated to five application amounts of biochar including 0%, 2%, 4%, 6%, and 8% by weight (0, 40, 80, 120, and 160 Mg ha−1, respectively). Sub-plots consisted of applications of 0 or 100 kg K2O ha−1. Soil pH decreased after 6 years and approached the initial level before biochar application to the soil. Soil nutrients such as calcium, magnesium, and potassium decreased over time. In general, edamame yield improved with potassium application regardless of the biochar rate of application.