WATER LOGGED SOIL
Meaning of water logged soil: Submerged soils are soils that are saturated with water for a sufficient long time in a year.The soil is intermittently saturated with water, oxidation of organic matter is slow and it accumulates in the in "A" horizon. In the second horizon Fe and Mn are deposited as rusty mantels or streaks if the diffusion is rapid they are deposited as concretions.In submerged soils due to diffusion of oxygen in the water, the organic form nitrogen undergoes minaralization to form NH4 to NO2 and NO2 to NO3 takes place in the aerobic layer. But in an anaerobic layer the absence of oxygen inhibits the activity of the nitrosomnas microorganisms that oxidizes NH4 and nitrogen mineralization stops at the ammonical form the accumulation of NH4 on submerged soils take placed the NH4 diffuse aerobic volatilization and nitrification the NO3 nitrogen in aerobic layer diffuses into reduced zone undergoes denitrification to form N2.The availability of N decreases on submerged conditions due to denitrification, volatilizations of ammonia, ammonium ions fixation by clay minerals leaching and runoff NO3 and NH3.
Different type of water logging in the field
Riverine flood waterlogging: In the rainy season, flood may come to the nearby land from the river having excess floodwater.Oceanic floodwater logging. Ocean water spreads in the nearby land cause waterlogging.Seasonal water-logging. Ran off water accumulates in the low lands and depression in the rainy season.Perennial water-logging. Deep water, swamp etc, get rain water run off water and seepage water from canal causing perennial water-logging.Sub soil water-logging. High water table in the rainy season is normally ansuitable for root growth.
Factors affecting formetion of water-logging
- Climatological factor: due to high rainfall water accumulates on the soil surface.
- Flood: Flood water is usually causing water-logged situation in the field .
- Seepage from canal: Ground water levels are cllloser to the surface due to seepage from canal
- Land shape: Saucer-shaped land gets water from high-lands whichresults into water-logging
- Uncontrolled and unwanted irrigation:excess irrigation may cause accumalation of water on the soil surface
- Drainage:poor drainage system is responsible for water-logging in the field.
Problems of water-logged soils are
- Water depth: Low land areas are usually flooded to depths of about 50 cm and the limitations to crop production associated with extensively low reduction potentials and partly because of low phosphorus availability.
- 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.
- Soil structure: Continuous water stagnation destroys the soil structure and makes the siol compact
- Soil temperature: water-logging lower down the soil temperature. Moist soila have a higher specific heat than dry soils.
- Soil pH: There are reversible pH change of the floodesoil, pH tends to increase in acidic soils and decrease in alkaline soila, undoubtedly pH is alter towards narmal.
- Availability of nutrients: Nitrogen- nitrogendeficiency is extremely common in water-logged soila. Due to lower temperature and reduced condition, mineralization of organicnis affected.
- Phosphorus: The inorganic form of P are usually present at higher lelels in flooded siols thenin upland soils
- Potassium. 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: Sulphur deficiency has been reported from many lowland area. The reduction of SO4 in flooded soils has three implications for rice culture: the S supply may become insufficient ,Zn and Cu may be immobilized, and H2S toxicity may arisse particularly in soils low in Fe.
- Zinc: Widespread deficiency of Zn to rice crop in wetland conditions is reported. Zinc is most frequently deficient in alkaline soils.
- Salinity.salinity is an important constraint to rice production in many coastal lowlands as well as in alkaline soils.
- Iron and Managanese: Fe and Mn are available in excess causing toxicity to the plant
- Effect on crops: Under water-logged condition all field crops connot survive due to poor aeration and uaavailability of nutrients to the plant. Only rice is an exception.
MANAGEMENT OF WATER -LOGGED SOILS
- Levelling of land: Leveling of land in many wetlands removes water by run off.
- Drainage: Drainage removes excess water from the root zone thet is hamful for plant growth. Land can be drained by suaface drainage, sub-surface drainage and drainage well methos.
- Controlled irrigation: Excess use of water in the irrigation results in water-loggd area
- To check the seepage in the canals and irrigation channaels:Due to seepage, land becomes water-logging
- Flood control measures: Construction of bunds may check wate flow from the rivers to the cultivable lands.
- Plantation of tree having high transpiration rate:Transpiration rate in certain tree like Eucalyptus, acacia, zyzyphus is very high.In transpiration process the underground water is consumed by trees, thus, lowering the ground water table.
- Selection of crops and their proper varieties: Certain crops like rice waternut,jute and sesbania can tolerate water-logging upto same extent. In rice crop submergence tolerance varies from one variety to another. Generally, lowland and deepwater varieties.
Submergence tolerant crops and their varieties
Situation of water-logging
Flood(water-logging for short period)
Water table near the surface and sometimes water-logging
Sita, kanak, Sujata,
Nutrient management in water-logged soils: low N fertility is an important contraint in the water-logged area the predominant from of inorganic N in lowland soils is NH4
The following concept may increase N-use efficiency in lowland rice:-
1. Deep placement
2. Slow and controlled release fertilizers
3. Use of nitrification and ureas inhibitors
Submitted by naipictuasdharwad on Fri, 09/04/2010 - 15:20