Innovations in agronomic management to improve maize productivity

Winans, Eric Thomas

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https://hdl.handle.net/2142/116148 Copy

Description

Title

Innovations in agronomic management to improve maize productivity

Author(s)

Winans, Eric Thomas

Issue Date

2022-06-27

Director of Research (if dissertation) or Advisor (if thesis)

Below, Frederick E

Doctoral Committee Chair(s)

Below, Frederick E

Committee Member(s)

• Moose, Stephen P
• Studer, Anthony J
• Martin, Nicolas F

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)

• maize
• corn
• nitrogen
• yield
• kernel
• yield component
• plant population
• plant density
• row spacing
• hybrid
• fertilizer placement
• banding
• sidedress
• agronomic management
• fungicide
• semi-dwarf
• brachytic
• nutrient uptake
• nitrogen uptake
• NUE
• recovery efficiency

Abstract

Sizeable gains in maize (Zea mays L.) yield have been achieved over the last several decades, primarily due to intensive breeding efforts and better crop management. However, on-farm maize yields fall short of the yield potential of modern hybrids. This yield gap (the difference between a farmer’s actual yield and potential yield) can be minimized by improving our understanding of the management and genetic factors that have the greatest impact on yield. Historical yield increases have been met with higher planting populations of hybrids with greater tolerance to stresses. As planting populations continue to rise, agronomic management strategies, in conjunction with hybrid selection, will necessitate a heightened focus on relieving density stress. Nitrogen (N) is the mineral nutrient that most often limits crop yield and is required in the greatest quantities for maize production. However, the overapplication of N in efforts to achieve higher maize yields can negatively impact the environment. To improve N use efficiency (NUE) and limit losses to the environment, nutrient availability must be synchronized with crop demand, which might be achieved through optimization of the 4R’s of nutrient stewardship, including the right placement, timing, rate, and source of N fertilizer. Nitrogen use efficiency has improved indirectly as maize yields have increased, and the introduction of semi-dwarf traits to maize hybrids could further improve NUE and allow for higher planting densities and improved crop harvest index. There is substantial interest in growing shorter maize hybrids than those commercially available, which could provide many physiological and practical advantages. It is expected that short-stature maize would have reduced crop loss and improved plant standability in challenging environmental conditions. Additionally, shortened internodes extend in-season crop access allowing for tailored crop protection and nutrient management solutions. Continued maize yield increases in the U.S. will necessitate new technologies in agronomic management that better realize the full yield potential of modern hybrids. This Ph.D. research hypothesizes that substantial maize yield gains can be realized by combining management practices that support higher planting populations and maximize season-long photosynthetic capacity. Additionally, commercially available maize hybrids are expected to exhibit wide variation in response to these agronomic management practices and can be characterized accordingly. Nitrogen fertilization in these high-yielding environments can be better managed to match the seasonal demand of plant uptake without sacrificing yield potential. Lastly, short-statured brachytic2 maize hybrids can be agronomically managed for higher yields like current maize hybrids while using crop inputs more efficiently. Exploring these statements encompassed four research areas: What is the gap between maize yield under typical farming practices and obtainable yield under intensive agronomic management, and which management factors are most important for closing this yield gap? Combining the management practices of narrower row spacing, higher plant population, balanced and season-long fertility, and foliar protection increased maize yield by 25% across 13 studies compared to standard farming practices in the central Corn Belt, demonstrating the apparent yield gap that can be improved through better crop management. Narrow row spacing (0.51 m) and fertility to provide N-P-K-S-Zn-B were the management factors that provided the most significant yield benefit, and these factors became more critical when maize was planted at a high population (109,000 plant ha-1). The yield contribution of each management factor was generally greater when applied in combination with all other enhanced factors than when added individually to the standard input system. How do commercially available maize hybrids differ in their ability to achieve higher yields in response to enhanced agronomic management? Identifying high-yield management practices highlighted the importance of quantifying the variation among commercial maize hybrids for their yield responses to these management practices. Across 63 hybrids and five environments, the largest yield responses were obtained when using foliar protection products (+0.9 Mg ha-1) and narrowing the row spacing (+0.8 Mg ha 1). Among these hybrids, there was a wide range in their yield responses to the different agronomic management practices, and grain yield had the highest heritability when grown under adequate fertility levels and in the narrow row arrangement. Longer-maturity hybrids tended to be higher-yielding and had greater yield responses to supplied fertilizer. Additionally, hybrids could be identified as either high yielding under typical agronomic management or highly responsive to intensive agronomic management. Despite these results, it was clear that the overall yield level and the yield responses to agronomic management were primarily determined by the environment. Can maize grain yield, seasonal N uptake, and N use be improved by optimizing the placement and timing of N application? Applying supplemental N fertilizer in the first two studies did not consistently increase yield compared to maize receiving the standard rate of N. Thus, more sustainable and economical use of N fertilizer requires better management, like placement or timing, of N while using responsible rates. Split-applying N between planting and mid-vegetative growth stages can better synchronize N availability in the soil with crop N demand. However, the response of maize to sidedressed N may depend on early-season N sufficiency to maintain yield potential. Subsurface banding of N at planting increased grain yield at four of the seven environments (by 0.4 to 0.8 Mg ha-1) compared to when N was broadcast applied, and no effect on plant stand was observed. The response to N placement or timing was more consistently observed at the southern Illinois locations where soil organic matter and pre-season residual NO3-N levels were relatively low. At those sites, maximum yield was typically observed when 25-75% of total applied N was banded at planting and the remainder of N was sidedressed at the V6 growth stage. Conversely, when N was broadcast applied, the highest yield was achieved when the total N rate was split evenly between planting and sidedress. When averaged across the environments, banding only 25% of N at planting increased yield by 0.7 Mg ha-1 compared to the more standard practice of broadcast applying all of N prior to planting. Compared to when N was broadcast applied, banding N increased plant recovery of the fertilized N in six environments primarily through greater N uptake after reproductive silk (+20%) and secondarily through greater N uptake prior to silking (+4%). Results suggest planter technologies allowing N to be concentrated in safe proximity to the seed allow growers to deescalate the agronomic and economic risks of delaying the application of some N until vegetative stages while reducing spring-time N rates. What are the agronomic characteristics, nutrient demands, and yield levels of pre-commercial brachytic2 maize hybrids across different agronomic conditions? Short-stature maize hybrids have recently been developed in commercial germplasm and are near launch, requiring information on their yield performance and nutrient requirements under different agronomic conditions. Yields obtained across six Illinois environments were greater than county averages in the same years and similar to tall hybrids grown at the same locations in a separate study, and on average, yield responded favorably to sidedress N (+0.4 Mg ha-1), broadcast or banded P-K fertility (+0.4 Mg ha-1), foliar protection (+0.8 Mg ha-1), and narrower rows (+1.0 Mg ha-1). Significant yield responses were observed when increasing the plant population from 109,000 to 129,000 plants ha-1 in 0.51 m row spacing at two locations. Across environments, plant and ear heights increased in response to soil fertility level, and short stature hybrids exhibited superior standability compared to tall hybrids grown in the same environments when faced with strong winds. The average harvest index of the short-stature maize hybrids was 0.59, which was associated with greater nutrient internal efficiencies and lower grain nutrient removal coefficients compared to values found in the literature. This research provides an initial indication that improved standability, greater yield responses to plant population and inputs, and more efficient use of nutrients can be realized with short-stature maize.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Eric Winans

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