IT-AGRI UNIT 3

• Environmental Factors


  • Climate
  • Edaphic (Soil)
  • Biotic
  • Genetic
  • Economic
• Precipitation


  All water that falls from the atmosphere such as rainfall, snow, hail, fog, and dew
• Rainfall is one of the most important factors influencing the vegetation of a place
• The distribution of rainfall is more important than total rainfall to have a longer growing period, especially in drylands
• Temperature


  Intensity of heat energy
• Increasing global temp. Will result in more hot and fewer cold extremes at both daily and seasonal time scales
• Annual surface evaporation will increase with temperatures; however, over land, evaporation will be linked to precipitation
• Relative Humidity (RH)


  The ratio between the amount of moisture present in the air to the saturation capacity of the air at a particular temp
• If RH is 100% = high H2O in the atmosphere ( 40-60% is suitable for most of the crop plants
• Very few crops can perform well when relative humidity is very low
• Solar Radiation


  • Biomass production by photosynthetic processes requires light
  • All physical processes depend on light
  • Controls the temp and crop distribution
  • Visible radiation is significant in the photosynthetic mechanism of plants
  • Photosynthetically Active Radiation (PAR) is Essential for producing CHO and biomass
• Wind Velocity


  Affects plant growth and development
• Atmospheric Gases for Plant Growth

  • CO2 for photosynthesis
  • O2 for respiration and photosynthesis
  • Nitrogen fixed in the soil
  • Toxic gases like SO2, CO, CH4
• Nitrogen is the most abundant gas in the atmosphere (78%)
• Oxygen is the second most abundant gas in the atmosphere (21%)
• Argon is the third most abundant gas in the atmosphere (0.96%)
• Edaphic (Soil) Factors


  • Soil water
  • Mineral nutrients
  • Soil temperature
  • Aeration
  • Soil pH
  • Organic matter
  • Soil biota
• Soil Moisture


  • The moisture range between field capacity and permanent wilting point is available to plants
  • Clay soil holds more water than sandy soil
  • Helps in the chemical and biological activities of soil including mineralization
  • Nutrient availability and mobility increase with an increase in soil moisture content
• Soil Texture


  • Sand - ↓water, cohesion/adhesion
  • Silt - = water
  • Clay - ↑water, lateral movement
• Soil Air


  • Aeration of soil is absolutely essential for the absorption of water by roots
  • Germination is inhibited in the absence of O2
  • O2 is required for respiration of roots, microbes, and nutrient mineralization
  • Potato,tobacco, cotton linseed,tea, and legumes need higher O2 in soil air
  • Rice requires a low level of O2 and can tolerate waterlogged
• Soil Temperature


  • Influences the rate of absorption of water and solutes (nutrients)
  • Affects the germination of seeds and the growth rate like tapioca sweet potato
  • Controls the microbial activity
  • Cold soils are not conducive to the rapid growth of most agricultural crops
• Soil Minerals


  • The minerals of the soil are derived from the weathering of rocks
  • These are the sources of plant nutrients eg; Ca, Mg, S, Mn, Fe, K etc.
• Soil pH


  • Acidic soil (<7.0), neutral (=7.0), saline and alkaline (>7.0)
  • Fe and Al are soluble in low pH
  • Low pH also interferes with the availability of other plant nutrients
• Soil Organic Matter


  • Supplies all the major, minor and micronutrients to crops
  • Improves the texture of the soil
  • Increases soil water retention
  • Organic acids released during the decomposition of organic matter enable mineralization
• Soil Organisms


  • Essential in decomposition and nutrient cycling
  • Microbes in the soil fix N to plant usable form for plants through symbiotic (Rhizobium) or non-symbiotic (Azospirillum) association
• Biotic Factors


  • Plants - Crop competition occurs when there is a nutrient demand
  • Animals - Soil fauna and flora help with nutrient cycling, while insects are mainly in pollination
• Physiography


  Surface features of the land, such as topography, altitude, or land cover
• Genetic Factors


  • Salinity and drought tolerance
  • Resistance to lodging
  • Chemical composition of grains
  • Quality grains
  • High yielding crops
  • Quality straw (biomass)
  • Pest tolerance
• Economic Factors


  • Prevailing farm condition
  • Availability and cost of planting materials
  • Pest and disease resistance
  • Availability of labor cost
  • Farming system and security
  • Available technology
  • Marketability and profitability