Date of Award

Summer 8-16-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Yong-Jiang Zhang

Second Committee Member

Francis Drummond

Third Committee Member

Seanna Annis

Additional Committee Members

M. Susan Erich

Lily Calderwood

Jay Wason

Abstract

The wild blueberry crop is one of the most important commercial crops in Manie, USA. Some new fertilizers claimed to enhance both conventional and organic wild blueberry production, but no scientific research has been done to test their effects. Besides, no scientific research has explored whether nutrition in wild blueberry plants is related to their physiological and morphological characteristics. Further, changed temperature and rainfall patterns related to global climate change have altered the growth pattern and nutrient economy of the wild blueberry system, bringing in new challenges to this traditional agricultural system. Therefore, the objectives of my dissertation were: 1) To characterize climate change patterns of wild blueberry production regions and determine their effects on crop health to manage the fields efficiently; (2) To test techniques using biochar-compost pellets and mulch to mitigate potential increased water deficits of wild blueberries, and 3) To quantify the effects of different commercial foliar fertilizer products on wild blueberry physiology and production, To fulfill objective 1, trends in the temperature, precipitation, and potential evapotranspiration (PET) during the growing season (May–September) as well as their effects on the Maximum Enhanced Vegetation Index (EVI) were analyzed for 26 wild blueberry fields in Downeast Maine over the time period of 1980 to 2019 in Chapter 2. Annual and seasonal climate trends (temperature, rainfall, snow cover) from 1980 to 2020 for seven Maine counties with large wild blueberry areas were analyzed in Chapter 3. These analyses were conducted using Remote Sensing software and Geographic Information System (GIS) tools in Arc GIS Pro software. The air temperature of the studied wild blueberry fields in Downeast showed higher rates of increase than those of the entire region (blueberry fields and non- blueberry production areas) during 1980-2019. An optimum temperature and PET for EVI of 22.4 °C and 145 mm/month suggest potential negative effects of further warming and increasing PET on crop health and productivity. Across all blueberry production fields, historical temperatures increased significantly in the fall and winter followed by summer, but not in the spring. Additionally, precipitation increased by 0.5–1.2 mm/year in the winter and fall, whereas no changes were found in the spring and summer. The rate of increasing temperature was comparatively slower in the warmer barrens located towards the south- west (Hancock to York). Moreover, the growing season lengthened towards the fall consistently in all locations, whereas lengthening towards the spring was inconsistent. To fulfill objective 2, the effects of warming and soil amendments (mulch and biochar-compost mix) on the physiology, growth, and yield of six different genotypes of wild lowbush blueberry plants at two different locations (Jonesboro and Deblois) in Maine were tested in Chapter 4. Open-top chambers with active heating were used to simulate climate warming, and crop physiology and yiield were measured. Some physiological performance, growth, berry yield and size of wild blueberry plantsunder warming treatment. The studied biochar-compost mix retained more moisture in the studied wild blueberry field soil, which helped the plants grow better with better physiological performance whereas a 0.5” (1.3 cm) layer of mulch amendment was not sufficient. Moreover, the plants growing under the warmer environment along with the biochar-compost mix amendment had the highest fruit production. Therefore, it would be beneficial to use a soil amendment like biochar-compost mix for wild blueberry crops under predicted warmer and drier summers. To fulfill objective 3, the impacts of seven foliar fertilizers and a standard granular fertilizer were tested on wild blueberries for one crop cycle (2019-2020) in a randomized complete block design with eight replicates in a conventional wild blueberry field in Maine, USA in Chapter 5. Soil-applied fertilizers containing N, P, K, as well as foliar fertilizers containingCa and/or plant hormones might benefit crop growth, but the impact on yield was limited. Moreover, wild blueberry physiology, morphology, and leaf nutrients in the vegetative year largely impact their yield in the following crop year. In Chapter 6, a follow up study was conducted on the use of nanocellulose (CNFs) with one of the foliar fertilizers to verify its promising result on wild blueberries found in Chapter 5. The effects of CNFs on the leaves of two wild lowbush blueberry species (Vaccinium angustifolium and Vaccinium myrtilloides) were investigated. Our study showed that the CNF addition significantly affected the surface wettability and water loss of the V. myrtilloides leaves but not the V. angustifolium leaves. The difference could be related to denser trichomes in V. myrtilloides leaves. Our study also revealed that the CNFs assisted the foliar fertilizer to disperse into smaller particles on the leaf surface of V. angustifolium species, which might have resulted in a higher average fruit yield, inviting further study.

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