Author ORCID Identifier
http://orcid.org/0000-0002-4667-2799
Date Available
12-25-2024
Year of Publication
2024
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Agriculture
Department/School/Program
Plant and Soil Sciences
Advisor
Dr. Hanna Poffenbarger, Dr. David H. McNear Jr.
Abstract
Supporting a growing human population under the duress of a changing global climate is arguably the greatest challenge faced by today’s world. Over the last century, agricultural development has primarily focused on improving grain yields to increase production of food, fuel, and fiber. However, recent work has emphasized that agroecosystem management can potentially help mitigate the climate crisis by storing atmospheric carbon in the soil as soil organic carbon (SOC). Furthermore, a growing body of research has focused on the critical role that roots play in building SOC. Maize crops occupy a substantial portion of the world’s cropland. As yields have increased with the development of new hybrids, research has characterized changes to aboveground maize organs. Despite the critical role that roots play in crop productivity, less is known about how they have changed over this time because labor-intensive, destructive, and low-throughput methods have commonly limited root research. My research sought to phenotype historic and modern maize hybrid root systems in the field in a high throughput manner and measure their potential effect on unique root traits and SOC pools.
To achieve this, a hayfield that was in place for more than 50 years was converted into a continuous maize cropping system. Two historic and two modern hybrids from the Pioneer Hi-Bred Maize Era Panel were planted at era-relevant planting densities in May 2021 in a randomized complete block design. To phenotype the root systems of modern and historic hybrids, minirhizotrons were installed each year at planting to collect root images at multiple in-season growth stages, and soil cores were also collected to measure root biomass. To maximize experimental throughput, novel strategies using deep-learning based segmentation models were tested to identify and measure roots captured in minirhizotron images. An iterative approach to model development was determined to be the best approach to accurately measure roots in minirhizotron images collected over multiple growth stages. By using this iterative approach to model development, modern maize hybrids were found to have less total root length than historic hybrids despite producing the same amount of root biomass. These results suggest that improved maize grain yields are linked to a smaller, more efficient root system.
Furthermore, this experiment characterized short-term SOC dynamics in continuous maize agroecosystems. Before converting the experimental site into a maize cropping system, I collected baseline soil samples in the existing hayfield at the plot level. Following the first harvest in 2021, a residue removal treatment was imposed as a split-block design to measure the contribution of root vs aboveground carbon inputs to SOC. Three years later, in 2024, soil cores were collected and fractionated to measure total, particulate, and mineral-associated SOC pools. These SOC pools were compared to the baseline SOC to quantify the impact that residue management, planting density, and contrasting root systems have on SOC pools. The treatments imposed largely had no impact on total SOC stocks or maize-derived SOC stocks. There was no relationship between maize-derived SOC and total root length or root biomass, and cumulative total biomass C inputs was weakly related to the formation of maize-derived SOC. Treatment effects are possibly limited due to the short-term nature of this experiment and more time is likely required for this site to reach equilibrium following land use change.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2024.485
Funding Information
This study was supported by the United States Department of Agriculture National Institute of Food and Agriculture (grant no.: 2019-67019-29401) in 2019.
Recommended Citation
Banet, Travis A., "MEASURING MODERN AND HISTORIC MAIZE ROOT PHENOTYPES AND THEIR IMPACT ON SOIL ORGANIC CARBON" (2024). Theses and Dissertations--Plant and Soil Sciences. 186.
https://uknowledge.uky.edu/pss_etds/186
