After reading this article you will learn about the types and detrimental effects of water-logging.
Types of Water-Logging:
Water-logging is following types:
(1) Riverine flood water-logging:
In the rainy season, flood may come to the nearby land from the river having excess flood water.
(2) Oceanic flood water-logging:
Ocean water spreads in the nearby land and causes water-logging.
(3) Seasonal water-logging:
Run off water accumulates in the lowlands and depressions in the rainy season.
(4) Perennial water-logging:
Deep water, swamp etc., get rain water, run off water and seepage water from canal causing perennial water-logging.
(5) Sub-soil water-logging:
High water table in the rainy reason is normally unsuitable for root growth.
Detrimental Effects of Water-Logging:
Flooding with consequent crop submergence is a problem in many of the lower lying wetlands. Detrimental effects of water-logging are discussed.
(1) Water depth:
Lowland areas are usually flooded to depths of about 50 cm (shallow rainfed lowland, and medium-deep) and the limitations to crop production associated with extensively low reduction potentials and partly because of low phosphorus availability.
In the ‘deep-water’ (flooding to depths of 50 to 100 cm) and ‘very deep-water’ or ‘floating’ (water depth more than 100 cm) areas, the principal problem of rice production is the tendency for the rice crop to be submerged for periods of up to 10 days or more.
(2) Poor aeration:
Due to water-logging, a part of the soil air moves out into the atmosphere as it is displaced by the incoming water. Inadequate supply of oxygen either retards or ceases plant growth as the accumulated carbon dioxide hampers the growth of the plant roots. Poor aeration results in the development of toxin and other injurious substances. Only rice plants can survive poor aeration due to water-logging.
(3) Soil structure:
Continuous water stagnation destroys the soil structure and makes the soil compact.
(4) Soil temperature:
Water-logging lowers down the soil temperature. Moist soils have a higher specific heat than dry soils. Consequently, a moist soil has lower temperature than dry soil. Low temperature affects the microorganism activity which consequently lowered the rate of nitrogen-fixation.
(5) Soil pH:
There are reversible pH change of the flooded soils, pH tends to increase in acid soils and decrease in alkaline soils, undoubtedly pH is alter towards normal.
(6) Availability of nutrients:
Nitrogen. Nitrogen deficiency is extremely common in water-logged soils. Due to lower temperature and reduced condition, mineralization of organic N is affected.
The inorganic forms of P are usually present at higher levels in flooded soils than in upland soils. An experiment showed that reduction of the soil by flooding decreases P absorption by 28-70%.
K response is apparent in many lowland soils. Flooding and puddling of the soils during lowland preparation may considerably increase the soil solution concentration of K because of displacement of exchangeable K by the large amounts of Fe++ and Mn++ in the soil solution.
Sulphur deficiency has been reported from many lowland areas. The reduction of SO4– in flooded soils has three implications for rice culture; the supply may become insufficient, Zn and Cu may be immobilized, and H2Stoxicity may arise particularly in soils low in Fe.
Widespread deficiency of Zn to rice crop in wetland conditions is reported. Zinc is most frequently deficient in alkaline soils.
Iron and Manganese:
Fe++ and Mn++ an available in excess causing toxicity to the plant.
Salinity is an important constraint to rice production in many coastal lowlands as well as in some poorly drained in land areas.
(8) Effect on crops:
Under water-logged condition all field crops cannot survive due to poor aeration and unavailability of nutrients to the plant. Only rice is an exception.