Lecture Notes on Factors Affecting Plant Growth

Introduction to Climate and Weather

• Weather: Describes short-term atmospheric conditions (meteorology).
  • Examples: Midwest, rainforest.
• Climate: Long-term average weather (climatology).
  • Examples: North Dakota vs Texas climates.
• Weather influences daily and seasonal crop growth.

Climate Influence on Crop Growth

• Crop Adoption and Distribution:
  • Climate suitability determines crop adaptation.
  • Certain plants are frost-tolerant; others are not.
  • Example: Wheat grows well in Kansas and Washington State.

Microclimate Definition

• Microclimate: Environmental conditions near the ground, affecting plant portions.
  • Example: Different microclimates in areas with trees vs open areas.

Precipitation in the United States

• Variation in precipitation from West to East and North to South.
  • High precipitation in parts of California, Oregon, and Washington.

Factors Affecting Plant Growth

• Weather Components:
  • Light intensity and duration.
  • Temperature, precipitation, wind direction, and velocity.
  • Relative humidity and air pressure.
• Impact on crop growth is hourly, daily, weekly, and season-long.

Light and Electromagnetic Radiation

• Visible Light: Part of the electromagnetic spectrum visible to humans.
  • Composed of rainbow colors from Violet (380 nm) to Red (700 nm).
• Effects of Light on Plants:
  • Plants use light wavelengths between 400 nm and 700 nm.
  • Visible spectrum colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet.
• Solar Constant: Energy received by Earth, with a portion absorbed, scattered, and reflected.

Climate Change and Earth's Reflectivity

• Albedo Effect: Reflectivity of Earth's surface, especially at poles.
  • Snow and ice reflect 85% of sun’s rays.
• Climate Feedback Loops:
  • Warming leads to ice melt, reduced albedo, and increased warming.
  • Impact on Arctic and Antarctic ice and global temperatures.

Water's Role in Crop Growth

• Water Use Concepts:
  • Evapotranspiration (ET): Water lost from soil and transpiration.
  • Water use efficiency: Crop yield per unit of water used.
  • Transpiration ratio: Water transported per unit of dry matter.
• Factors Affecting ET:
  • Increases with temperature, wind, light, soil moisture, and leaf area.
  • Decreases with high relative humidity.

Drought Stress and Crop Development

• Impact on physiological processes, cell enlargement, and photosynthesis.
• Critical Stages:
  • Corn and soybean development stages affected by drought and temperature.

Water Cycle and Agricultural Practices

• Importance of managing water for crop efficiency.
• Farmers aim to use less water while increasing yields.
• Techniques:
  • Nutrient balance to prevent water wastage.
  • Understanding soil water holding capacity and plant transpiration.

Conclusion

• Emphasis on sustainable agriculture practices.
• Importance of monitoring and managing climate impacts on farming.

Please review the videos and readings suggested and prepare any questions for the next session.