Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant Science

Advisor

Jianjun Hao

Second Committee Member

Robert Larkin

Third Committee Member

Rober Bayer

Additional Committee Members

Bee Chim

Benjamin King

Abstract

The potato, Solanum tuberosum, was first brought to Maine in the mid-1700’s and has remained economically important since. In 2023, Maine was the ninth largest US producer with a total production of over two billion pounds. However, potato production can be impactful to soil health as the result of crop management practices. The effects of different management factors in potato production (rotation length, variety selection, use of non-grain rotation crops, green manure rotations, chemical fumigation, and compost amendment) were evaluated over four years. No differences were found in the first year of potato planting, but significant differences in soil health parameters were observed in the subsequent potato planting year. In this study, five parameters were found to be related to both management factors and yield, percent organic matter, percent total organic carbon, copper, phosphorus, and zinc. Compost amendments increased organic matter, total organic carbon, zinc, many microbial groups detected via phospholipid fatty acid (PLFA) assays, and was significantly positively related to yields. Rotation length was negatively correlated with organic matter, copper, phosphorus, zinc, and yields, although this could be attributed to few rotation cycles. Fumigation was not positively correlated with yield nor disease incidence reduction compared to standard practices. Other factors resulted in fewer impacts to soil health and yields. The majority of fungi present in Maine soils were identified as various types of saprotrophs, and the largest phyla of bacteria detected was Proteobacteria. Fungi were found to be more sensitive to management factors than bacteria. Compost amendment appeared to positively impact soil microbial communities and fumigation appeared to negatively impact them. A novel organic soil amendment, post-processed lobster shell, was also explored as a soil amendment. While impacts to microbial communities were not clear, significant reductions in severity of potato early dying was observed in plots which were fumigated and then amended with lobster shell meal, compared to fumigated and unamended plots. The results of these studies could aid Maine potato farmers in developing crop management plans which can improve soil health, reduce disease, and increase yields.

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