1. Which factor causing waterlogging suggests extensive irrigation?
a) Impervious Obstruction
b) Excessive Rains
c) Over and Intensive Irrigation
d) Seepage of Water from High Lands
Explanation: When intensive irrigation is practiced, it only irrigates a small portion of the whole irrigable land. Due to this over irrigation it leads to heavy percolation which leads to rising of water table causing waterlogging. So, to prevent waterlogging extensive method of irrigation is recommended.
2. Seepage of water from the adjoining highlands causes waterlogging.
a) True
b) False
Explanation: The water present in the highlands gets seeped into the sub-soils of the affected areas. This leads to the rise of water table causing waterlogging.
3. Waterlogging is the rise of water table.
a) True
b) False
Explanation: The water which seeps deep down to the ground gets collected at some point and forms under water table. Due to some reasons the level of this table gets raised up to the top soil level. Here further water cannot seep down and it gets stagnated on the top surfaces of the soil. This stagnation of water due to the rise of water table is called waterlogging. Therefore we can say that the waterlogging is the rise of the water table.
4. For maximum productivity of crops both surface and sub-surface drains are sometimes needed.
a) True
b) False
Explanation: Surface drains are needed for crops cultivated on flat lands to remove excess irrigation water, whereas subsurface drains are needed for soils having poor internal drainage and high water table. So, therefore for maximum productivity of crops both surface and subsurface drains are sometimes essential especially in regions of high water table.
5. How can tile drainage help to increase crop yields?
a) Increases Free Gravity Water
b) Increases Volume of Soil
c) Decrease Air Circulation
d) Increases Water Table Level
Explanation: The tile drainage helps in lowering the water table level which in turn increases the crop yields. It also helps in increasing the volume of soil from where the roots of the crops can obtain food.
6. Tile drainage helps to reduce soil erosion.
a) True
b) False
Explanation: As tile drainage helps in lowering the groundwater level, it gives room for increase in volume of the soil and helps the roots to hold on to the soil very tight. It also provides well drained soil to hold rainfall, resulting in less runoff. Due to these reasons, the soil erosion is reduced by tile drainage.
7. Which type of soils is benefited by using tile drainage?
a) Dry Soils
b) Black Soils
c) Wet Soils
d) Red Soils
Explanation: Tile drainage requires less labour and time in tilling and harvesting the soils as these do not obstruct farming. Planting in wet soils may decrease crop yields. So, therefore the delay in planting and decrease in crop yields in wet soils can be improved by using tile drainage.
8. In what chemical ways does tile drainage help in plant growth?
a) Decreases Alkalinity of Soils
b) Increases salinity of Soils
c) Increases Nitrogen
d) Reduces and Removes Toxic Substances
Explanation: Tile drainage helps in reducing and removal of toxic chemicals and substances like sodium and other soluble salts, which harms the growth of plants.
9. Under what strata the tile drainage should not be placed?
a) In Shallow Depths
b) More Pervious Strata
c) Less Pervious Strata
d) Pervious Strata
Explanation: The tile drainage should not be placed under or below the less pervious strata because in this case, the drains may remain dry even though the land above the impervious strata may be logged as this water will not reach the drains.
10. What structure is surrounded around the tile drains when used in less pervious strata?
a) Envelope Filters
b) French Drains
c) Beehive Grate
d) Surface Inlet
Explanation: Envelope filters surround the tile drains when used in less pervious strata. These filters help in increasing the effective tile diameter and in turn help increasing the inflow rate, and also help in preventing the inflow of soil into the drains.