This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Salinity and Water-logging”.
1. A land is said to be water-logged when _______________
a) the aeration is stopped in the root zone due to the rise in water content
b) there is a reduction in crop yield
c) there is an accumulation of alkali salts in the root zone of the crop
d) there is salinity in the soil
Explanation: A land is said to be water-logged when the productivity of land gets affected and the crop root-zone gets deprived of proper aeration due to the flooding or high water table. It represents a saturated condition of the soil especially that of the crop root-zone with water. It also leads to the salinity of the soil.
2. What is the pH range for strongly alkaline soils?
a) 7.4 – 7.8
b) 7.9 – 8.4
c) 8.5 – 9.0
d) > 9
Explanation: Very strongly alkaline soils (pH>9) and ultra-acidic soils (pH<3.5) are very rare. The USDA classifies soil pH for alkalinity as follows:
|Slightly alkaline||7.4 – 7.8|
|Moderately alkaline||7.9 – 8.4|
|Strongly alkaline||8.5 – 9.0|
|Very strongly alkaline||> 9.0|
3. Presence of excessive moisture retards the bacterial activities affecting crop growth.
Explanation: Presence of excessive moisture lowers the temperature of the soil. In low temperatures the bacterial activities are retarded and their growth rates are also affected. It affects the soil-crop badly as soil microbial activity is disturbed.
4. Which of the following statement is wrong?
a) Seepage drains reduce the chances of water-logging
b) Untimely maturity of the crops is the characteristic of water-logged lands
c) The percolation loss can be reduced by keeping the intensity of irrigation low
d) There is no way to keep a watch over the problem of water-logging
Explanation: By observing variations in the ground-water level is one of the ways of keeping a check on the problem. It can be done by measuring the depth of water levels at regular intervals in the wells dug in the area.
5. The phenomenon of water-logging can be best understood with the help of a Hydrologic equation.
Explanation: Hydrologic equation:- Inflow = Outflow + Storage
Inflow represents the amount of water that enters the sub-soil in various processes. The term outflow represents mainly evaporation from the soil, transpiration from plants, and underground drainage of the track. The term storage represents a change in the ground-water reservoir.
6. Swampy land is ________
a) ill-aerated land
b) the land where cultivation operations are impossible
c) land having deposition of alkali salts in the root zone of the crops
d) saline land
Explanation: The normal cultivation operations such as tilling, ploughing is difficult in wet soils. The cultivation operation becomes impossible if the free water may rise above the surface of the land in extreme cases. Such land is called swampy land.
7. Salinity increases the osmotic activity of the plants.
Explanation: Due to efflorescence, there is a deposition of salts on the surface of soil forming a thin crust after the evaporation of water. Land affected by that is saline soil and the soil water surrounding the roots of the plants reduces the osmotic activity of the soil.
8. Which of the following is a remedial measure for water-logging?
a) Controlling seepage from the canals
b) By lowering the F.S.L of the canals
c) Quick disposal of rainwater
d) Installation of lift irrigation systems
Explanation: Installation of lift irrigation system is one of the remedial measures adopted to reclaim the water-logged area and others are preventive measures which keep the land free from water-logging. It is found to be a very effective method of reclaiming water-logged land.
9. Which of the following factor do not contribute to water-logging?
a) Inadequate drainage
b) Seepage from unlined canals
c) Frequent flooding
d) Excessive tapping of groundwater
Explanation: The various factors that contribute to the rise in water table i.e. water-logging are –
• Over and intensive irrigation
• Seepage of water through canals and adjoining high lands
• Inadequate natural drainage and surface drainage
• Excessive rains and submergence due to floods
• Impervious obstruction.
10. Which one of the following is not a remedial measure for waterlogging?
a) Good drainage for irrigated land
b) Conjunctive use of water in the basin
c) The lining of canals and watercourses
d) Contour bunding
Explanation: Contour bunding or contour farming is the sustainable land management practice of planting or farming across a slope. The following are the measures adopted for controlling waterlogging are –
• Canal lining
• Crop rotation and optimum use of water
• Provision of intercepting drains
• Reducing the intensity of irrigation
• Improving the natural drainage system and providing an efficient drainage system.
Sanfoundry Global Education & Learning Series – Irrigation Engineering.
To practice all areas of Irrigation Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.