Field Drainage system

1. Drainage:

• It is the artificial removal of water in excess of the quantity required for the crop.
• Includes removal of surface and sub-surface water in the root zone.

Terms

a) Critical water logging duration:

• It is the maximum allowable duration of flooding at given growth rate of crops.
• If water logging is allowed to continue beyond this duration, growth and yield of crops would be adversely affected.

b) Drainage coefficient:

• It is the rate at which water is removed in 24 hours by a drain.

Mathematically.

Drainage coefficient (DC) = Amount of water to be drained/ critical water logging duration.

• It is expressed in cm or m.
• The removal of 10⁵ liters in 24 hours equals drainage of 1.157 liter/sec.
• It helps to determine the size of drain.

c) Drainage depth:

• It is the depth of excess water to be drained from an area.
• The amount of drainage depends on land use, extent of water logging, causes of water-logging, soil condition, types of crop and cultural practices.

Water logging

• It is a condition of land where the ground water stands at a level that is detrimental to plants.
• May result from over irrigation, flooding, seepage or lack of drainage.

Causes of water logging

• Heavy rainfall and over irrigation.
• Low elevation and flatness of land adjacent to the sea.
• Seepage from the reservoir.
• Flooding of lowlands due to overflow of river.
• Flat topography
• Salt accumulation
• Inadequate soil management practices
• Natural obstruction to flow of ground water
• Inadequate surface drainage

Effects of water logging

• Reduces soil aeration. Results to root damage due to prolong water logging.
• Uptake of nutrients is affected.
• Volume of nutrients uptake by roots is affected.
• Leads of salinity due to deposition of salts on surface.
• Soil temperature is lowered, soil structure is destroyed and healing capacity of soil reduced.
• Plants nutrients loss due to leaching and water flow.
• Yield loss from 20-100%.

Importance of drainage

• Helps in soil aeration
• Decreases erosion by increasing water infiltration into soil
• Assures high soil temperature
• Provides more available soil moisture and plant food by increasing the depth of root zone of soil.
• Permits the removal of excess salts and alkali.
• Facilitates early ploughing and planting
• Lengthen the crop growing season.