Test: Reclamation & Waterlogging in Soil - Civil Engineering (CE) MCQ

A land is said to be water-logged when its productivity gets affected by the high water table. The productivity of land gets affected when the root zone of the plants gets flooded with water.

The life of a plant depends upon the nutrients like nitrates and the form in which the nitrates are consumed by the plants is produced by the bacteria, under a process called nitrification.
These bacteria need oxygen for their survival. The supply of oxygen gets cutoff when the land becomes ill aerated, resulting in death of these bacteria, and fall in production of plant’s food and consequent reduction in the plant’s growth, which reduces the crop yield.

In case of leaching, the land is flooded with adequate depth of water. The alkaline salts present in the soil, get dissolved in this water, which percolate down to join the water table. The process is repeated till the salts in the top layer of the land are reduced to such an extent that some salt resistant crop can be grown. High salt resistant crops like fodder, berseem, bajra etc., are now grown on this leached land for one or two seasons.

The salts injurious to the health of plants are alkali salts e.g., Na₂CO₃, Na₂SO₄ and NaCI. Such a salt affected soil is unproductive and is known as saline soil. If the soil is saline and the efflorescence continues for a long period, then soils become ill aerated and highly unproductive and these are called alkaline soils. These soils can be reclaimed by,
(i) Leaching
(ii) Providing surface and subsurface drainage of the area 
(iii) Crop rotation
(iv) Lining of canals and water courses
(v) Reducing the intensity of irrigation.
(vi) Optimum use of water
(vii) Gypsum addition
Acidic soils, on the other hand, can be reclaimed by basic salts such as limestone.

Leaching is the process in which land is flooded with adequate depth of water. The alkaii salts' present in soil, get dissolved with this water which percolate down to join the water table or are drained away by sub-surface drains,
Leaching requirement, 
D_d is Depth of water drained out per unit area
D_i is Depth of irrigation water applied per unit area

EC_i is Electrical conductivity of irrigation water
EC_d is Electrical conductivity of drained water.