Course Content
Learn Principles of Agronomy — B.SC agriculture
About Lesson
  1. Solar radiation:
  • Solar radiation performs two essential functions.

a. Provide light for direct growth and development functions in the plants.

b. Provides heat that governs and indirectly affects various physiological processes in the plant.

  • The instrument that is used to measure total incoming radiation is called pyranometer.
  • Intensity, duration and quality of solar radiation, which control growth and development in the plants.
  • The duration of radiation controls photoperiodism and the intensity and quality control the
  • physiological processes in the plants.

  1. Temperature:
  • Temperature affects the physical and chemical processes within the plants.
  • The diffusion rate of gases and liquids change with temperature.
  • Solubility of different substances depends upon the temperature.
  • The stability of the enzyme system is affected by the temperature.

  1. Relative humidity (RH):
  • Determines the rate of evaporation and transpiration.
  • The higher the relative humidity, the less is the evapo-transpiration and vice versa.
  • High humidity favors the growth of fungi and other crop pests.
  • About 70-80% RH is considered optimum for crop production.

  1. Wind:
  • Wind is indirectly responsible for causing rainfall and changing the humidity of a certain places.
  • Directly, the gentle wind is responsible for promoting photosynthesis by supplying CO2 in the deeper leaf layer of plant canopy.
  • Gentle wind helps to pollinate the crop plants, water uptake, conduct proper metabolism, and regulates the temperature of plant canopy.
  • Hot dry wind is harmful for crop plants because such wind accelerates the transpiration and evaporation from the soil causing desiccation of plants.
  • It also affects the photosynthesis by the closing of stomata.
  • High wind velocity causes lodging of crops, breakage of plant parts, shattering of grains, flower drops and uprooting of whole plant.
  • In desert and light soil containing field the high wind velocity causes more soil erosion also.
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