Agroecosystem

• System - collection of interdependent parts functioning as a whole
• Ecosystem - ecological system

  Components

  1. biotic
  2. abiotic

  Interactions - of the components & their exchange of matter & energy
• Ecosystem Structure

  • how the components are organized
  • the way they relate to each other to make a whole

  1. Spatial or temporal
  2. Trophic structures
• Abiotic

  1. Resources - can be consumed
  2. Conditions - not directly consumed
• ECOSYSTEM FUNCTION

  ❖ energy flow

  ❖ productivity

  ❖ nutrient cycles
• Laws of Thermodynamics

  1st LAW - energy is neither created nor destroyed

  2nd LAW - approach a state of entropy
• Biotic


  10% Law of Energy Transfer
• Production - refers to energy accumulated in a particular trophic level

  ❖ Gross Production – total production (energy harvested)

  ❖ Net Production – energy remaining in excess of respiration

  ❖ Respiration – portion of energy expended for maintenance & performance of activities

  NP = GP – R
• Productivity

  • refers to the rate at which production is harvested by a given trophic level (cal per m2 per day, kg per ha per yr)

  Biomass or Standing Crop

  Net production accumulates over time as biomass

  GP – R > 0 (biomass increases)

  GP – R < 0 (biomass decreases)

  GP/R = 1 (biomass constant)
• Food Chain - sequence of organisms feeding on each other

  Food Web - interlocking food chains

  Trophic Level - expression of an organism’s feeding status in an ecosystem
• Nutrient Cycling

  ❖ movement of nutrients through an ecosystem by the use of different biogeochemical cycles

  ❖ nutrients exist in either a reservoir or an exchange-pool
• Ecosystem Classification

  ❖ aquatic ecosystem (lake, marine)

  ❖ terrestrial ecosystem (forests, grassland, deserts)

  ❖ agricultural ecosystem

  ❖ urban & industrial ecosystem
• Agroecosystem

  ❖ interaction of living organisms with one another & their environment under a man-managed

  agricultural system

  ❖ any ecosystem largely created & maintained to satisfy a human want or need

  ❖ can be manipulated to improve production & to produce more sustainably, with fewer

  negative environmental or social impacts & fewer external inputs.
• AGROECOSYSTEM PROPERTIES

  Productivity

  ✓ net output of valued product per unit resource output

  ✓ measured in terms of yield & income

  ✓ quantity of food, fuel or fiber that the ecosystem produces for human use

  Equitability

  ✓ the distribution of products & benefits from the ecosystem

  ✓ sharing agricultural production fairly

  Sustainability

  ✓ ability of a system to maintain productivity & withstand major disturbances

  Stability

  ✓ degree to which productivity is free from variability caused by mild disturbances

  ✓ associated with diversity

  ✓ consistency of production
• Natural Ecosystem vs. Agroecosystem

  A)

  B)

  
• Rainfed vs Irrigated

  
• Population - population refers to a group of

  individuals belonging to the same

  species occupying the same place

  at a particular time
• METAPOPULATION

  • sink population
  • source population
  • dispersal (migration)
• POPULATION

  (STRUCTURE & PROPERTIES)

  • population size vs density
  • temporal vs spatial dimensions

  - uniform, clumped, random
• Sampling - representative of the population

  taken for the purpose of estimating

  pest density and diversity in the field
• SAMPLING UNIT

  area within the sampling universe from which

  measurements are taken, eg. traps, plant, leaf,

  small area, a quadrat
• Characteristics of a Good Sample

  • should be reliable enough
  • should be large enough to cover or represent the population
  • easy to understand and follow
  • cost effective or inexpensive
  • should be yielding reliable results
  • material or equipment to be used are readily available
• Methods of Sampling

  1. Direct method - counting the number of insects present, number of weeds or pests in the host or in the environment
  2. Indirect method- assess pest injury through symptoms
• Weed cover and density sampling

  1. Choose an area as representative (1 m x 1 m quadrat)
  2. Quadrat is laid at random area three times
  3. Identify, count, clipped all the weed species inside the quadrat
• Methods of Chemical Application

  1. Broadcast application
  2. Band application
  3. Spot treatment
• Tank - a leakproof storage of the spray material; holds the liquid.
• Pump - develops the pressure which forces the liquid materials out of the tank.
• Pressure regulator -maintains pressure at the desired level.
• Pressure gauge - indicates pressure and at the same time tells if the other parts of the

  sprayer are functioning properly.
• Boom - distributes the spray solution to nozzles.
• Nozzle - breaks the liquid into spray droplets.
• Strainer/filter - keeps the larger particles from going to the pump or prevents foreign matter or dirt from clogging the nozzles.