Drake Elting

Date of Award

2024

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Ryba, Tyrone

Area of Concentration

Biology

Abstract

Soil microbes have a direct impact on plant and soil health. The unsustainability of contemporary agricultural practices pose an increasing threat to the food security of human societies, as many of these practices result in the degradation of soil health, upon which future productivity is reliant. A number of studies have affirmed the assertion that organic farming methods such as milpa increase microbial diversity which has been shown to increase nutrient bioavailability and can help the restoration of damaged soil. The present study investigates the comparative bulk soil microbiome between maize, bean, and squash monocultures and maize, bean, and squash intercropping modeled on the milpa agroecosystem as to provide insight on the potential benefits of intercropping practices on the maintenance of soil health. A field experiment was conducted during the month of July at the Oxford College Organic Farm with seven treatments: maize, bean, squash, maize-bean, maize-squash, bean-squash, and milpa (maize-bean-squash). DNA was extracted from a total of 20 samples and sequenced by Zymo Research using 16s rRNA sequencing for bacterial identification and ITS1/2 sequencing for fungal identification. The samples underwent quantification using qPCR and automated electrophoresis and the final library was sequenced on Illumina MiSeq. Results revealed that a total of 2,634 bacterial and 727 fungal operational taxonomic units (OTUs) were observed. Microbial diversity results were inconclusive regarding if intercropped samples displayed greater soil microbial diversity when compared to monoculture samples. While there does appear to be a nominally significant association between the microbiome of the samples when divided between monoculture (maize, bean, and squash) and intercropped (maize-bean, maize-squash, bean-squash, and milpa) sample types, more research would need to be done under improved experimental conditions to confirm any possible association.

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