Q. 155.0( 1 Vote )
What will be the
If the farmer floods his field everyday then the water will get collected in the surrounding and it has following disadvantages:
• excess water and wet soil do not permit proper aeration of the seed /root of the plants
• Water logging increases the amounts of salts in the soil and damages the soil fertility.
Water logging occurs whenever the soil is so wet that there is insufficient oxygen in the pore space for plant roots to be able to adequately respire. Other gases detrimental to root growth, such as carbon dioxide and ethylene, also accumulate in the root zone and affect the plants.
Plants differ in their demand for oxygen. There is no universal level of soil oxygen that can identify waterlogged conditions for all plants. In addition, a plant’s demand for oxygen in its root zone will vary with its stage of growth.
Effects on plant growth
Low levels of oxygen in the root zone trigger the adverse effects of water logging on plant growth. Water logging of the seedbed mostly affects germinating seeds and young seedlings. Established plants are most affected when they are growing rapidly. Therefore, if a soil becomes waterlogged in July, final yields may not be greatly reduced; soils are cold, the demand for oxygen is low and plant growth is slow at this time of year. Prolonged water logging during the warmer spring period could be more detrimental, however the probability for this to occur is much lower than water logging in July.
When plants are growing actively, root tips begin to die within a few days of water logging. The shallow root systems that then develop limit the uptake of nutrients (particularly nitrogen) and water, particularly when the soil profile starts to dry in spring. As a result plants may ripen early and grains may not fill properly.
Nitrogen is lost from waterlogged soils by leaching and de-nitrification (degassing). De-nitrification leads to the gaseous loss of nitrous oxide (N2O) into the atmosphere, which is a major greenhouse gas. These losses, together with the lowered ability of plants to absorb nutrients from waterlogged soil, cause the older leaves to yellow.
Water logging also directly reduces nitrogen fixation by the nodules of legume crops and pastures.
Thus the crops should be given specified amount of water.
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