1. Pipe drains run _______________
a) longitudinally on the bed and transverse to the length of canal on the side slopes
b) longitudinally to the length of the canal on the side slopes and transverse to the bed
c) longitudinally to the length of the canal
d) transverse to the bed
Explanation: Provision of open-jointed pipe drains is one of the methods of drainage arrangements. It will run longitudinally on a trench excavated below the lining on the canal bed along the length of the canal and transverse to the length of the canal on the side slopes.
2. Which of the following statement is wrong about the requirement of good lining?
a) The lining should be able to withstand the differential sub-soil pressure
b) Brick lining, concrete lining or precast slab lining can be easily repaired as compared to cast-in-situ concrete lining
c) The hydraulic efficiency generally reduces with time
d) Brick tile lining may provide better abrasion resistance than cement concrete and boulder lining
Explanation: A canal may have to transport a considerable amount of sediment load which damages the lining by abrasion. Cement concrete and stone boulder linings provide better abrasion resistance as compared to the brick tile lining.
3. Which type of lining is adopted when the channels have become stable and no danger of scouring is expected?
a) Brick lining
b) Single burnt clay tile lining
c) In-situ cement concrete lining
d) Flexible membrane lining in the bed and rigid lining on the sides
Explanation: The burnt clay tile lining is to be adopted at places where aggregates for the manufacture of concrete are not available economically. The brick lining is used where seepage considerations are important. In-situ cement concrete lining is provided when the canal has a bed width greater than 8 m.
4. 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.
5. 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:
| Denomination | pH range |
|---|---|
| Slightly alkaline | 7.4 – 7.8 |
| Moderately alkaline | 7.9 – 8.4 |
| Strongly alkaline | 8.5 – 9.0 |
| Very strongly alkaline | > 9.0 |
6. Presence of excessive moisture retards the bacterial activities affecting crop growth.
a) True
b) False
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.
7. 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.
8. The phenomenon of water-logging can be best understood with the help of a Hydrologic equation.
a) True
b) False
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.
9. 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.
10. Salinity increases the osmotic activity of the plants.
a) True
b) False
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.