1. ROLE OF DRAINAGE IN CROP PRODUCTION NextEnd

2. 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 CO 2 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 CO 2, 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. NextPreviousEnd

3. 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. NextPreviousEnd

4. 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 can’t 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. NextPreviousEnd

5. 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). NextPreviousEnd

6. Causes for water-logging (Cont)…  Water-logging is caused when in- flow into ground water exceeds out- flow from it.  The problem is serious when hydraulic conductivity of the soil is less than 2.5 cm/hour.  Heavy rainfall and over-irrigation in humid regions are the main causes for water-logging.  In the river basins and deltas, when there is high rainfall, water is not drained quickly due to low infiltration rate of the soil. NextPreviousEnd  Vast areas in the deltas of Ganges, Brahmaputra, Godavari and Mahanadi in India are waterlogged.

7. 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. NextPreviousEnd

8. 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 NextPreviousEnd

9. 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)…. NextPreviousEnd

10. 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%. NextPreviousEnd

11. Drainage Remedial measures adopted in surface flooded areas (due to inundation by floods) include channel refinement and improvement, providing structures to prevent entry of flood waters into cultivated areas, embankments, detention dams, anti- erosion schemes, detention basins, diversion of flood waters, watershed management, sea walls etc. In the case of drainage congestion in irrigation areas, measures adopted are surface drainage, lining of canals to prevent seepage, sinking of tube wells to depress the ground water table etc. NextPreviousEnd

12. 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. NextPreviousEnd

13. 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. NextPreviousEnd