ROLE OF DRAINAGE IN CROP PRODUCTION

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ROLE OF DRAINAGE IN CROP PRODUCTION
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Abstract

• Removal of excess quantity of water in both
  surface and sub-surfaces of root zone is called
  as drainage.
• Excess water reduces the availability of oxygen
  in the root zone and accumulation of CO2 and
  other harmful gases.
• Water logging in command areas cause salinisation
  and resulted in great loss of crops.
• Several physiological, morphological and
  anatomical changes happen due to water logging
  and resulted poor crop. Providing adequate
  drainage facilitates ready oxygen supply to root
  zone, eliminate ill gases such as CO2, methane
  etc.
• Besides improving the nutrient availability,
  improving soil characteristics and ultimately
  yield of crops.
• Learning objectives
• To study the causes for water logging and their
  ill effects on crop production
• To learn the role of drainage in crop growth and
  production of crops.

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Introduction

• Drainage is the artificial removal of water in
  excess of the quantity required for the crop.
• Drainage includes removal of excess water of both
  surface and subsurface in the root zone of crops.
• Irrigation and drainage go together and are not
  mutually exclusive.
• Irrigation aims at supplying optimum quantities
  of water throughout the crop period, whereas,
  drainage aims at removing excess quantity of
  water in a short time.
• Often, both may be required together to assure
  sustained and high level production of crops.

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• Excess water causes great harm to the crop by
  reducing availability of oxygen to the root
  system and accumulating carbon dioxide and other
  gases in root system
• Drainage of excess water from irrigated fields is
  necessary for satisfactory growth and yield of
  crops.
• In parts of West Bengal and Assam, India where
  rainfall is heavy, drainage is necessary for even
  water loving crops such as rice.
• There are areas where crops cant be sown in
  proper sowing time, because of standing water on
  the fields or excessive moisture in the root zone
  of the crop, unless efficient drainage is
  provided.
• Not only accumulated surface water due to heavy
  rainfall or flood, but also, excess water in the
  field due to over-irrigation or seepage from
  adjacent canal or tributary and percolation of
  irrigation water from the fields are the main
  causes for water logging and has to be drained.

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Drainage in irrigation projects

• In the planning of most of the irrigation
  projects in the world in general and India in
  particular, provision was not made for adequate
  drainage in the command area.
• Water table has increased steadily due to high
  seepage and percolation losses, consistent
  over-irrigation and spillage from canal systems.
• Water-logging and salinisation have spread
  considerable acreage in the command area resulted
  in low production or out of cultivation.
• For efficient working, irrigation canals have to
  be designed and constructed such that full supply
  level is above ground level (either in full or
  part embankment) and drainage ditches have full
  supply level below ground (either in full or part
  cutting).

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• Low elevation and flatness of lands adjacent to
  the sea suffer from water-logging by the
  intruding of sea-water during high tide.
• Seepage from the reservoir with large water
  spread and canals running over long distances,
  over-irrigation and non-provision of drainage in
  irrigation projects have led to water-logging.
• Floods in rivers spread to cultivated land during
  high storms and cyclones and cause water-logging.
• Overland flow, underground seepage from adjacent
  areas etc., causes water-logging.

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Effects of water-logging in crop production

• Water-logging is generally defined as the
  condition where water table is less than 3cm from
  the surface.
• At this depth, water from the water table rises
  at significantly rapid rates by capillary action
  to the ground surface.
• Water-logging causes several changes in the soil
  and plant resulting in reduced growth and in some
  cases death of plants.
• The degree of injury depends on type and stage of
  crops, period of water-logging, type of soil and
  weather prevailed in that area.
• Susceptible crops for water-logging are tobacco,
  tomato, pulses and chilli. The most resistant
  crop for water-logging is rice

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The following are effects of water-logging

• Water-logging reduces soil aeration.
• This results in reduction of oxygen supply to the
  crops root system.
• There is also a buildup of carbon dioxide,
  methane, ethane and profane in the soil, which
  are harmful to the crop root system, ultimately
  complete root damage to the crops.
• Oxygen concentration in the soil is about 17-20
  and when it falls to less than 10 due to
  displacement of air in the soil pores by water,
  growth of the plant is inhibited.
• Morphological, anatomical and physiological
  changes are taking place due to water-logging.
• Enlarging shoot length, senescence, abscission,
  and production of adventitious roots in crop
  plants.
• Proportion of aerenchchymatus tissues in the
  root system increases.
• Respiration in the roots turns towards anaerobic
  from aerobic, results in accumulation of toxic
  substances and decay of roots.
  (Cont).

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• Ethanol production increases and activity of
  alcohol dehydrogenase increases in roots of
  plants.
• Ethanol in large amount is harmful to crops.
• Due to anaerobic conditions in the root zone,
  uptake of nutrients is affected.
• Due to restriction of root growth, the volume of
  soiltapped by the plant roots for nutrients is
  restricted.
• Due to capillary rise of soil water by
  evaporation on the surface of the soil, salts are
  brought to the surface layer and salinity
  results.
• Soil temperature is lowered, soil structure is
  destroyed and bearing capacity of the soil is
  reduced.
• Plant nutrients such as nitrates are lost through
  leaching and denitrification increase nitrogen
  deficiency.
• Yield of crop is reduced or even zeroed. The
  average loss in yield varies from 20-100.

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Benefits of drainage

• Draining the land provides conditions favorable
  for crop production.
• The greatest benefit of drainage relates to
  aeration. Good drainage facilitates the ready
  diffusion of oxygen to the root zone and escape
  of carbon dioxide from the root zone into the
  atmosphere. Several harmful gases also escape
  from the root zone into the atmosphere.
• The activity of aerobic organisms which influence
  the availability of nutrients such as nitrogen
  and sulphur to plants depends on soil aeration
  and hence, drainage improves aerobic organisms.
• Toxicity in acid soils due to excess iron and
  manganese is decreased by drainage (due to
  presence of oxygen in the root zone).
• Drainage permits roots to grow deeper and spread
  wider thereby increasing the volume of soil from
  which nutrients can be extracted.
• The removal of excess water helps in drying of
  the soil quickly and optimum soil temperature
  permits timeliness of field operations.
• The provision of a good drainage system permits
  the removal of excess salts in the soil or
  irrigation water and prevents their build up in
  the upper soil layers.

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Summary

• Drainage is the artificial removal of water in
  excess of quantity beyond the requirement of the
  crop.
• Excess water causes great harm to the crop by
  reducing availability of oxygen to the root
  system and accumulating carbon dioxide and other
  gases harmful to the root system.
• Water-logging reduces aeration in soil, alters
  morphological, anatomical and physiological
  characters of plants, ethanol production
  increases, yield of crop is reduced or even
  zeroed.
• By drainage, several harmful gases escape from
  the root zone into the atmosphere which provides
  healthy soil system, improves availability of
  nutrients, better root system and in turn
  increase in yield of crops.

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