Subsurface Irrigation
Water is applied below the ground surface through a system of pipes or porous materials.
Aim → to reduce evaporation losses & maintain an artificial water table near root zone.
Suitability
- Hot & arid climates with high evapotranspiration (ET).
- Where surface application is difficult (saline/sandy areas).
- High-value & perennial crops.
Pitcher Pot Irrigation (traditional subsurface method)
- Mud pots with small holes buried around plant root zones.
- Holes closed with a conducting material/thread to regulate seepage.
- Covered with soil–sand mulch mix.
- Water seeps slowly and continuously into root zone.
- Best for widely spaced fruit trees under water-scarce conditions.
Advantages
- Low evaporation loss.
- Less weed growth (only root zone wetted).
- Very water efficient.
Disadvantages
- High installation & maintenance cost for modern subsurface systems.
- Soil must be permeable enough (not clayey).
- Risk of waterlogging if poorly designed.
III. Pressurized Irrigation Methods
Sprinkler Irrigation System (Point Source Method) Water sprayed into the air under pressure, falls like rainfall.
Suitability & Advantages
- Light, sandy soils with high infiltration.
- Shallow soils or undulating topography (no leveling needed).
- Water-limited areas (low stream size).
- Suitable for almost all crops except rice (needs standing water).
- Fertigation, pestigation, and herbigation possible.
- Controls crop canopy temperature & helps in seed germination.
- Saves land (no bunds, ridges).
Disadvantages
- Poor performance in windy areas (non-uniform distribution).
- Saline water → causes leaf burn, nozzle clogging, pipeline corrosion.
- High initial & operational cost.
- Continuous power supply required.
Major Components
- Pump set
- Mainline, sub-mains, laterals
- Riser pipes with tripod stands
- Sprinkler heads
Classification
- Rotating head system (single or twin nozzle types).
- Perforated pipe system (small holes in laterals).
- Portable, semi-portable, and permanent systems.
Efficiency Measure
- Christiansen’s Uniformity Coefficient (Cu):
Cu =100 (1−ΣXm⋅n)
where,
m = mean depth of water,
n = no. of observations,
X = deviation from mean.
- Cu ≥ 85% → satisfactory.
- Drip (Trickle/Line Source) Irrigation
Water applied drop by drop at the root zone using emitters.
Suitability & Advantages
- Best for orchards, vegetables, flowers, plantation crops.
- Very high Water Use Efficiency (80–95%).
- Saves 50–70% water compared to surface methods.
- Reduces weed growth (only root zone wetted).
- Fertilizer application possible (fertigation).
- Improves yield and quality.
Disadvantages
- Very costly to install.
- Requires skilled maintenance.
- Emitter clogging by salts/sediments.
- Not economical for low-value field crops.
Components
- Overhead tank or motor pump
- Main line (50 mm poly pipe)
- Sub-mains (37 mm pipe)
- Laterals (12 mm poly pipe)
- Emitters (5–20 lph capacity: button, spray, microtube types)
- Fertilizer tank & filters
