Lecture on Modern Corn Production: Light Interception lec 37 pt 2

Modern Corn Production and Light Interception

Introduction to Light Interception

  • Doctor Ron Heineger discusses the role of light interception in modern corn production.
  • Key statistics: corn yield increases by approximately 3-4 bushels per year in North Carolina.
  • Factors influencing yield: selection of new genetics and the relationship between hybrid maturity and planting date.

The Role of Light in Corn Production

  • Corn plants act as factories: they intercept light (radiation) and convert it into starch.
  • Uses of corn starch: animal feed, ethanol production, corn syrup, food products, plastics, etc.
  • Goal of corn producers: maximize efficiency in converting intercepted light into grain.

Management Factors Affecting Light Interception

  • Controllable Factors:
    • Row spacing
    • Plant population
  • Uncontrollable Factors:
    • Weather conditions (cloudiness, brightness).

Population Wheel for Plant Density

  • Description of a population wheel: visual representation with varied row spacing (wider to narrower).
  • Range of plant population per acre: 12,000 plants (wider spacing) to approximately 44,000 plants (narrower spacing).
  • Plant growth behavior: taller plants indicate competition for light; shorter plants indicate limitations in resources (primarily water).
Observations from the Population Wheel
  • As plant density increases:
    • Height increases initially due to competition for light.
    • Beyond a critical point, height decreases due to competition for water/nutrients.
  • Desirable Growth: Taller plants resulting from optimum light interception without excessive stress.

Optimal Plant Population

  • The optimal plant population varies based on:
    • Hybrid genetics
    • Soil management
    • Water availability in specific regions.
  • Importance of knowing the narrow range for optimal plant population in corn, unlike soybeans which have a wider population range.

Row Spacing and Its Influence

  • Types of Row Spacing:
    • Common spacings: 30-inch, twin rows (7 inches between sets), and 15-inch row spacing.
  • Goals of changing row spacing: increase leaf area to capture more light, reduce wasted light on bare soil.
Data on Light Interception
  • Measurement of light interception in micromoles per second per meter squared using different row widths:
    • 18-inch rows show highest light interception early in the season compared to 36-inch and twin rows.
    • As the season progresses, light interception differences minimize once canopy closes.
Yield Implications of Row Spacing
  • Historical data demonstrates yield benefits with tighter spacing:
    • Increased yield observed when transitioning from 36 to 30-inch rows (approximately 6% increase) and from 30 to 20-inch rows (another 6%).
  • Cost-Benefit Analysis:
    • Changing row spacing may not always justify costs relative to yield gains.

Constraints in Corn Growth

  • Fixed leaf area limits further increase in light interception regardless of row spacing adjustments.
  • Main method to enhance light interception: increase the number of plants to expand leaf area.
Light Interception and Plant Population
  • Correlation between plant population and light interception:
    • Higher populations lead to greater light interception, especially in early growth stages.
    • The effect of increased populations becomes more pronounced later in the season, contributing effectively to yield maximization.
Effect of Plant Population on Ear Size
  • Graph illustrating relative ear weight against increasing plant population.
  • At 20,000 plants per acre: 100% ear size maintained.
  • Risks of stress indicated when populations exceed thresholds; maintaining ear size above 50% is essential.
Managing Stress During Corn Growth
  • Stress factors leading to ear size reduction are influenced by plant spacing rather than population count alone.
  • Stress factors reveal themselves at tight plant spacing, which result in malformed ears and loss of kernels.
Spatial Considerations in Planting
  • Visual representation of 20, 30, and 36-inch row spacings comparing plant distances in rows (12, 8, and 4 inches).
  • Ideal spacing promotes uniform ear size while avoiding stress during pollination.

Long-Term Observations on Corn Population

  • Data from multiple locations indicate optimal planting density at about 34,000 plants per acre before stress impacts yield.
  • Average increase of approximately 3 bushels per acre with each additional thousand seeds planted is seen as economically feasible.
  • Highlighting yield contest records shows potential without plateau effects, especially in high-yield environments.

Conclusion and Future Considerations

  • Emphasizing the delicate balance between achieving high plant populations and avoiding stress-induced yield reduction.
  • The next lecture will address strategies for reducing stress in corn production while maintaining optimal population density and spacing.