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Enhancing efficacy of agronomic management of maize through synergies with biostimulants
Woodward, Logan Patrick
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https://hdl.handle.net/2142/120134
Description
- Title
- Enhancing efficacy of agronomic management of maize through synergies with biostimulants
- Author(s)
- Woodward, Logan Patrick
- Issue Date
- 2023-04-28
- Director of Research (if dissertation) or Advisor (if thesis)
- Below, Frederick E
- Doctoral Committee Chair(s)
- Below, Frederick E
- Committee Member(s)
- Kent, Angela D
- Margenot, Andrew J
- Brown, Howard M
- Department of Study
- Crop Sciences
- Discipline
- Crop Sciences
- Degree Granting Institution
- University of Illinois at Urbana-Champaign
- Degree Name
- Ph.D.
- Degree Level
- Dissertation
- Keyword(s)
- Biostimulants
- Nutrient management
- Maize
- Nitrogen-fixing bacteria
- Phosphorus-solubilizing bacteria
- Abstract
- ABSTRACT U.S. maize (Zea mays L.) grain yield per area has consistently increased over the last several decades, primarily due to crop management and intensive breeding efforts. Maize growers have relied heavily on the use of fertilizers to strive toward high yields, resulting in public concerns surrounding the environmental impacts of fertilizer manufacturing, transportation, and off-target movement of nutrients. These issues have prompted the development of the 4R’s of Nutrient Stewardship in an effort to improve fertilizer use efficiency. Breeding efforts have increased the yield potential of modern maize hybrids, directly related to their greater toleration of crowding stress associated with higher planting densities. As a result, U.S. average maize seeding rates have consistently increased each year, associated with reductions in root size per plant, potentially limiting the ability of roots to support plants through the accumulation of necessary resources. These trends in maize agronomic production practices further demonstrate the need to discover innovative ways to improve utilization of fertilizer nutrients by maize plants to achieve high yields. Biostimulants may be supplemental factors to include in a grower’s agronomic management to reduce nutrient stresses as well as increase the efficiency of fertilizer use. Multiple studies and reviews have examined the effects of biostimulants on plant physiology; however, published research is often constrained to greenhouse and lab experiments. Most field-based studies researching biostimulant-facilitated effects on maize growth and development are implemented using traditional management systems. This research, however, investigated the interaction of biostimulant applications with progressive agronomic management to determine if biostimulants can enhance the value of progressive management on maize grain yield and fertilizer utilization. This Ph.D. research hypothesizes that the application of a nitrogen (N)-fixing bacterial inoculant can supplement and/or help to replace the reliance on synthetic N fertilizer by increasing N accumulation, promoting greater reproductive potential, and increasing grain yields of maize. Additionally, N-fixing bacteria may be a way to manage higher planting densities of maize by reducing nutrient stresses associated with smaller root systems. Lastly, combining multiple biostimulants may interact synergistically to enhance the effects of fertilizer treatment on growth, nutrient utilization, and yield of maize. Investigating these hypotheses led to three interrelated research areas: Can N-fixing bacterial inoculants serve as an additional source of N in maize production systems? An N-fixing bacterial inoculant, Proven 40®, was applied in-furrow at planting at varying N fertilizer rates ranging from 0-225 kg N hectare-1. When averaged across N fertilizer rates, Proven 40® increased V8 and R1 plant N accumulation by 5% and 4%, respectively. Increases in N accumulation in response to Proven 40® were observed in all plant fractions and ∂15N abundance parameters confirmed that some of this additional N uptake was derived from biological N fixation. At the V8 growth stage, Proven 40® supplemented the fertilizer equivalent of 22.5 kg N hectare-1 at intermediate N rates; while by the R1 growth stage, supplemental plant N uptake was comparable to an additional 18 kg hectare-1 of N fertility. The responses to Proven 40® treatment on plant N uptake were a function of increased biomass accumulation, with no effect on plant N concentration. Proven 40®-driven increases in plant N accumulation were associated with moderate but statistically significant increases in grain yield when averaged across the N rates, with the greatest numerical responses occurring at intermediate rates of fertilizer N. Grain yield responses to Proven 40® treatment were a function of increased kernel production, further inferring that this N-fixing bacterial inoculant is supplying biologically-fixed N at a time of high N demand when the kernel number per ear and yield potential are being determined. These results show that Proven 40® can serve as an additional source of N for maize that may potentially reduce the reliance on synthetic N fertilizer while maintaining high yields. Does the efficacy of N-fixing bacteria vary with changes in the size of a maize plant’s root system due to differing planting densities? Based on the success of the first study showing that N-fixing bacteria supplemented atmospherically-fixed N, this study was implemented to determine an agronomic management system where the grain yield effects of N-fixing bacteria are maximized. Increased planting density of maize decreases the size of an individual plant root system, potentially reducing its ability to accumulate water and mineral nutrients. The objective of this research was to determine if N-fixing bacterial inoculants can be utilized to counteract reductions in root biomass associated with greater planting densities to achieve greater yields. Two N-fixing bacterial inoculants (Proven 40® and NOD AL®) were applied in-furrow to maize planted at 74,000, 89,000, and 104,000 plants hectare 1. The greatest effects of two different N-fixing bacteria on yield were realized when applied to densities of 89,000 and 104,000 plants hectare-1, which are greater than the current densities used in the United States and Illinois. Numerical yield increases were observed from Proven 40® application for plants grown at 104,000 plants hectare-1 which were associated with increases in root biomass, relative root surface area, and average kernel weight. These data suggest that Proven 40® can promote root growth, indicating a greater ability of plants to acquire the necessary nutrient and water resources to achieve elevated grain yields at higher planting densities. Can multiple biostimulants be applied to increase the effects of banded fertilizer on maize grain yield and nutrient uptake? The “right placement” is one of the 4R’s of Nutrient Stewardship and subsurface banded applications of fertility can increase maize nutrient utilization and grain yield. However, with the increased interest in the use of biostimulants in row crop production, it is vital to determine how applications of multiple biostimulants interact in a synergistic way to further improve the effects of banded fertilizer on nutrient uptake and yield of maize. The biostimulants utilized in this study included an in-furrow-applied bacteria with phosphorus-solubilizing and N-fixing capabilities called iNvigorate® and foliar applications of a microbial enhancer called SourceTM applied with and without molybdenum (Mo). These biostimulants were applied with and without banded applications of a co-granulated fertilizer supplying N, phosphorus (P), sulfur (S), and zinc (Zn) called MicroEssentials SZ (MESZ). Banded applications of MESZ significantly increased maize grain yield and accumulation of N, P, and S. Compared to banded fertilizer alone, application of iNvigorate® further increased maize P (4%), N (2%), S (3%), and Zn (8%) uptake as well as promoting a 2% increase in grain yield. Additions of foliar applied SourceTM and Mo provided synergistic effects on P and N accumulation and P recovery efficiency, suggesting that multiple biostimulants can be utilized in a systems approach to enhance greater recovery and utilization of banded applications of fertilizer.
- Graduation Semester
- 2023-05
- Type of Resource
- Thesis
- Copyright and License Information
- Copyright 2023 Logan Woodward
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