agr12 factors

• Crop production


  Can be viewed from two perspectives: 1) at the CROP level, 2) at the SYSTEMS level
• Crop production at the crop level

  1. Y = f [G + E + (G x E)]

  2. where, Y = yield, G = genotype, E = environment, G x E = interaction of genotype and environment
• Genotype


  Genetic design of a plant which dictates the ceiling of how much a variety/cultivar can yield
• Environment


  Any factor external to the plant that influences its growth and development
• G x E interaction

  Interaction between genotype and environment
• A high yielding variety grown under poor environment will have low yield
• A low yielding variety grown in optimum (good) environment will still have low yield
• Ideal genotype


  One that has a wide range of environmental adaptability
• Optimum environment


  One that poses a minimum of constraints to crop growth and development
• Through G x E interaction, some particular elements of the environment may draw varying responses from different genotypes
• Practical implications of crop production at the crop level

  • Need for continuous development of improved varieties/cultivars
  • Develop management practices that can remove or avoid environmental constraints
  • Continuously assess G x E interactions
• Production system


  Includes inputs (controllable, manageable resources), system (component crops, processes and activities), environment (uncontrollable factors), and output (yield)
• Man (management) has only partial control of the production system
• Certain factors/conditions are given to which the system has to fit or adjust
• The design of the production system emanates from man (his needs, objectives, knowledge and capabilities)
• Environmental factors


  Includes climatic (above-ground) and edaphic (soil) factors (abiotic factors), and pests and beneficial organisms (biotic factors)
• Climate

  The seasonal pattern of a particular place occurring from year to year
• Weather

  A momentary state of the atmosphere brought about by the combination of elements, e.g., temperature, pressure, moisture content, air movements, radiation, etc.
• Macroclimate


  The climatic environment one meter above the plant canopy
• Microclimate


  The climatic environment one meter below the canopy in the case of tall plants or the climate within the leaf canopy for short (below one meter) plants
• Precipitation


  Any form of water particles falling on the ground in liquid or solid form (rainfall, hail, snow, etc.)
• Average rainfall in the Philippines = 2553 mm (Luzon – 2724 mm; Visayas – 2391.7 mm; Mindanao – 2349.8 mm)
• Role of water in plants

  • As a reactant in many biological reactions
  • Enters into the structure of biological molecules
  • Serves as medium of transport of nutrients and other substances
  • Helps regulate plant temperature
• Categories of plants based on need for moisture

  • Xerophytes - desert plants
  • Hydrophytes - aquatic plants
  • Mesophytes - land plants; most economically important plants
• Factors affecting amount and distribution of rainfall


  • Topography
  • Air circulation patterns
• Rain formation requires high relative humidity, sufficiently low temperature, condensation nuclei, and sufficiently low pressure
• Drought


  Insufficiency of rainfall/moisture which seriously affects plant growth
• Absolute drought


  29 consecutive days without rainfall of at least 0.25 mm
• Partial drought


  15 consecutive days without rainfall of at least 0.25 mm
• Temperature


  The degree of hotness or coldness of a body
• Cardinal temperatures


  • Minimum temperature - below which the velocity of the reaction becomes zero
  • Optimum temperature - where the velocity of the reaction is at maximum
  • Maximum temperature - above which the velocity of the reaction becomes zero
• Factors affecting temperature of the environment

  • Solar radiation
  • Surrounding land masses or bodies of water
  • Altitude
• Classification of crops according to temperature requirement

  • Cool season crops
  • Warm season crops
  • Tropical
  • Sub-tropical
• Effect of temperature on crops

  • Vernalization requirement for flowering
  • Effect on crop maturation
• Wind


  Air in horizontal motion
• Normal wind speed in the Philippines = 7.2 km/hr
• At 30 km/hr, leaf tearing may already occur especially in banana and abaca</b>
• Effects of wind on plants

  • Increase transpiration
  • Destructive effects of strong winds, typhoon
  • Sterility due to loss of pollens
  • Disease spore dispersal
  • Reduced CO2 levels especially in enclosed spaces
  • Affects plant form
• Air circulation in the atmosphere results from the sun's radiation falling more directly on the tropical regions than on the polar regions, the warmer air rises and flow forward the poles, cools and sinks as cold polar air and then returns toward the equator as ground flow
• Solar radiation


  Energy given out by the sun through radiation