Technological development in Sri Lanka's agriculture

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Protected houses.....

The crops of plants are nurtured in a confined environment with optimum temperature, humidity, nutrition and light conditions.

                                  



Importance of crops cultivation in conservation lands
  • Protection of crops from bad weather conditions.
          Example : Heavy rain falls, more wind, more sunlight
  • Protecting crops from disease impacts. It's prone to diseases but easy to control.
  • The yield can be obtained not only in season but also in off-season.
  • Market demand and price will rise due to quality yield.
  • The nursery techniques used are efficient.
  • Contamination of food, soil, water, air etc. will be avoided due to non-use or limited use of chemical for disease control.
Types of protected houses
  • Based on protect
  1. Full protected houses : These should be completely covered and shielded with UV-                                               impermeable polythene or glass or polycarbonate sheets. 

  2. Semi protected houses : Only half of the wall is covered by shade nets. The roofs are                                              covered with UV resistant polythene.
                                                           Example : Rain shelters, Shade houses

  • Based on durability
  1. Permanent houses : Example : Green house

  2. Less permanent houses : Example : polythene house

  3. Temporary houses : After the target is achieved the house can be removed and the                                         crop maintenance activities can be continued.
                                            Example : Propagator 

 
  • Based on the materials used for the installation
  1. Glass houses



  2. Polythene houses, poly tunnels/ Plastic houses

  3. Net houses, Shade houses

  4. Fiber glass houses

  5. PVC-Rigid panels houses

  6. Poly carbonate houses 

  • Based on shapes
  1. Arch shape
  2. Slanted roof
  3. Saw tooth type

  4. Top vent



The following factors can be controlled in protected land:
  1. Air 
  2. Light 
  3. Temperature 
  4. Humidity
Techniques used to control ventilation in protected houses
  • Use Ventilation fans, Exhaust fans
  • Use appropriate system for respective climate zones
                 Example : Top vent, Saw tooth vent structure 
  • Erection of windproof plant hedges
  • Raising the CO2 level inside the house to a special level by artificially injecting CO2 gas into the house
Techniques used to regulate light irradiance when it exceeds a specified level in protected houses
  • Using Alum net
  • Use of shade net or black color nets
  • Increasing crop plant density
  • Cutting of shade trees around the protected house area
Techniques used to regulate light transmittance when it falls below a specified level in protected houses
  • Use of glass or polythene for roofing
  • Use of artificial light sources - In the months of January, February and March,    sunlight is less. In these cases 25-30 Wm2 light should be provided on the plant with LED bulbs. For this it is important to provide 40% blue, 40% red and 20% white light.
Techniques used to control protected house's indoor temperature in protected houses
  • Increasing the height of the wall
  • Use of roof top opening windows - Open during the day and closed at night
  • Installation of Air conditioning system
  • Using Overhead Spraying mist System
  • Installation of Exhaust fans
  • Using fan pad
  • making protected houses by shade nets
Techniques used to regulate temperature when it drops in protected houses
  • For the interior of the walls, use a dark color paints
  • Using a heating coil
  • Supply of hot water and steam through pipes
Techniques used to control humidity rise in protected houses
  • Using fans
  • Using chemical Absorbents - Silica gel
 Techniques used to regulate humidity when it is low in protected houses
  • Using Sprinklers
  • Using Foggers
  • Hanging waterlogged sponge sheets on the side walls

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