Water logging occurs in soils when soil profile is completely saturated with water, and there is insufficient oxygen in the pore spaces for plant roots to be adequately respire. So this way ultimately, the level of carbon dioxide in soil is increased and effects on plants growth. There is no universal level of water logging in soil is identified because plant roots demand of oxygen in soil vary with growth stage. Waterlogged conditions cause reduction in root growth, ultimately reach to the plant root-rot disease so it effects to the plant till later. It is common observation for a plant that experienced to water logging condition, become deficient in phosphorus and nitrogen and especially sensitive, to the hot temperature. If these symptoms cannot properly observe, the yield loses can occur.
Water logging may be temporary or permanent: temporary mostly occurs due to heavy rain fall, but on the other hand permanent waterlogging occurs due to rise in water table depth. Water logging occurs due to many reasons but main reason is fallowing;
(1) Natural reason
(2) Human induced.
Natural reasons include Physiography of a watershed, Geology, weather, Soil type, Seepage inflows, Irrigation. And human induced water logging includes; over irrigation, seepage from canals, inadequate drainage, poor irrigation management, obstruction of natural drainage, land locked parches having no outlet, excessive rainfall, flat topography, occasional spills by floods, closed/contour.
Water logging and salinity in our soils major problem: Ones salinity occurs, then waterlogging fallow it. 20% of cultivable land area 8% is severely affected. According to soil salinity survey of Wapda estimated, that this problem becomes more sewer if this continues and increases up to 30%. SCARP programmed also have been launched about 2/3 have been completed out of 40 stations.
Water logging affects the crops in many ways as fallows; it causes delayed normal cultivation operations, which are adversely affects the presence of excess water in soil. Aquatics plants grow in soil that competes with our major crops. Sometimes in extreme water logging condition, only wild grow is there. It also causes disease decaying of roots, external symptoms on the foliage and fruits are common, and then ultimately reduced the yield of many crops. Cash crops cannot be cultivated and land is restricted to few crops. It also cause reduction in soil oxygen due to water filled soil pores and ultimately soil Co2 level increase and affects rot growth. Lack of aeration also cause of manganese precipitation that is toxic to plant.
Water logging affects the soils in many ways as fallows; due to water logging soil slowly warm up, restrict the seedling, seed germination, root development, also biotic activity also reduced, and ultimately nitrogen fixation and others function disturbed. Water logging build up soil salinity when water table becomes high, leaving the salts on the surface and evaporates. High salinity cause deposition of sodium and other salts in upper layer, ultimately they destroy the soil structure and may become for toxic for plants and other soils biota. Soil microorganism involve in nitrogen fixation process also surely affected and reduced plant growth.
Control measures of Water-Logging
- Installation of tube-wells for irrigation and vertical drainage
- Construction of surface-drains and tile-drains
- Lining of water-channels
- Planting of eucalyptus in water-logged areas.
- Planning and designing of future canals on proper lines.
- Providing artificial drainage system
- Lowering of water-levels of canals.
- Fixing cropping pattern
- Control intensity of water
- Optimum use of water
Athar Mahmood, Muhammad Umer Chattha, M.Umair, M. Adnan and M Mahran Aslam