Date Approved

5-2021

Graduate Degree Type

Thesis

Degree Name

Biology (M.S.)

Degree Program

Biology

First Advisor

Jennifer Winther

Second Advisor

Sheils Blackman

Third Advisor

Priscilla Nyamai

Academic Year

2020/2021

Abstract

Centuries of conventional till (CT) management in agriculture has depleted soil organic matter (SOM) by over 50%. While only comprising 5% in most soils, SOM provides soil with fertility and productivity. To compensate for SOM depletion, producers have been forced to increase their reliance on fertilizer and irrigation to maintain yields. In the coming decades, climate change is expected to challenge food production and threaten an already fragile system. With no remaining land left to cultivate, conservation management strategies such as no-till (NT) look to restore SOM and increase the resilience of food production for an ever growing, increasingly food insecure global population. An ecological outcome of NT management is the fostering of arbuscular mycorrhizal fungi (AMF). AMF are obligate biotrophs that form symbiotic associations with most terrestrial plants. Their plant host supplies organic carbon, and in return, AMF primarily enhance the acquisition of limiting nutrients and reduce osmotic stress. AMF also contribute to SOM through a protein glomalin, found in their cell walls which is deposited into soils during hyphal turnover. We performed a controlled greenhouse experiment with populations of AMF from CT and NT soils to isolate their influence glomalin yield and on corn and soybean growth under well-watered (WW) and drought stress (DS) conditions. NT soils used for AMF inoculum contained over 4X (p=0.01) the AMF spores as CT soils with a distinct community. Colonization rates ranged from 71-97% in corn, 69-95% in soybean and were generally higher in NT over CT and DS over WW. For both plants, AMF had the strongest influence on shoot growth particularly under WW conditions. Corn shoot biomass was reduced by both AMF communities under WW conditions (p=0.004), while soybean shoot biomass was increased by NT AMF (p=0.03). NT inoculum produced the most glomalin under WW condition for both plants. Much more work is required to understand the plant-fungal dynamics in agricultural ecosystems. Identifying and fostering beneficial relations between plants and AMF may be a strategy to reduce inputs while maintaining yields, increasing agricultural sustainability.

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