Which of the following processes of soil conservation is called 'mulching'?
- A.Stones, grass and soil are used to build barriers along contours.
- B.The bare ground between plants is covered with a layer of organic matter like straw.
- C.Different crops are grown in alternate rows to protect the soil from rain wash.
- D.Rocks are piled up to slow down the flow of water.
Correct answer
B. The bare ground between plants is covered with a layer of organic matter like straw.
Explanation
The correct answer is B. Mulching means covering the bare soil between plants with a layer of organic matter such as straw, dry leaves, husk or grass clippings. The cover shades the ground, so less water evaporates and the soil stays moist and cool, and it also softens the blow of falling rain, which would otherwise loosen the topsoil and wash it away. As the mulch rots it adds humus to the field, and by cutting off light it keeps weeds down. Farmers use it widely in orchards and vegetable plots, and in dry regions it is one of the cheapest ways to hold moisture. A is wrong because raising barriers of stone, grass and soil along the contours is contour barrier work. C is wrong because growing different crops in alternate rows is strip cropping. D is wrong because piling up rocks to slow the flow of water describes a rock dam. Exam tip: mulching covers the soil, strip cropping alternates rows, terracing cuts steps into a hillside.
Practice Questions
View allWhich of the following watershed development projects is sponsored by the Central Government and aims at enabling the rural population to conserve water?
- A.Arvary Pani Sansad
- B.Haryali
- C.Jal Kranti Abhiyan
- D.Neeru-Meeru
Show answer
Correct answer: B. Haryali
Explanation
The correct answer is B, Haryali. Haryali is a centrally sponsored watershed development project launched in 2003 by the Ministry of Rural Development, and its whole point is that the village panchayat plans and carries out the work itself. Under it gram panchayats build check dams, farm ponds, percolation tanks and contour bunds so that rain is held where it falls; wells recharge, and dryland farmers get water for a second crop. The watershed committee is chosen by the gram sabha, and the villagers share part of the cost and the upkeep of the structures. A is wrong because the Arvary Pani Sansad is a people's parliament of villages on the Arvari river in Alwar, Rajasthan, a community effort and not a central scheme. C is wrong because Jal Kranti Abhiyan was a later water awareness campaign of the water resources ministry. D is wrong because Neeru-Meeru was a state water conservation programme of Andhra Pradesh. Exam tip: Haryali 2003, central and panchayat-led; Neeru-Meeru is Andhra Pradesh; Arvari Pani Sansad is Rajasthan.
What should be the temperature difference between the upper layers and deeper layers of the ocean for setting up the OTEC power plant?
- A.40°C
- B.250°C
- C.50°C
- D.20°C
Show answer
Correct answer: D. 20°C
Explanation
The correct answer is D, 20°C. An ocean thermal energy conversion plant works only where the warm surface water is at least about 20 degrees Celsius hotter than the cold water drawn from the depths.
OTEC uses that difference as its heat source. The warm surface water boils a liquid with a low boiling point, such as ammonia, and the vapour turns a turbine to make electricity; cold water pumped up from roughly a kilometre down condenses the vapour back to liquid so the cycle repeats. The gap of 20 degrees is needed because a smaller one leaves too little energy to run the pumps and still send power out. Such conditions are found in tropical seas, and India has tested OTEC near the Lakshadweep and Andaman islands.
Option A is wrong because a 40 degree gap does not occur between the surface and the deep sea. Option B is wrong because 250 degrees belongs to a furnace, not the ocean. Option C is wrong because 50 degrees is far beyond any natural ocean difference.
Exam tip: OTEC needs a surface to deep water difference of about 20°C and works best in tropical waters.
The Kigali Amendment of 2016 to the Montreal Protocol provides for the phase down of
- A.Chlorofluorocarbons
- B.Hydrofluorocarbons
- C.Sulphur dioxide
- D.Methyl bromide
Show answer
Correct answer: B. Hydrofluorocarbons
Explanation
The correct answer is B, hydrofluorocarbons. Hydrofluorocarbons were adopted as substitutes for chlorofluorocarbons in refrigeration and air conditioning because they do not harm the ozone layer, but they turned out to be very powerful greenhouse gases, so the Kigali Amendment of 2016 brought them under the Montreal Protocol with a schedule for reducing their use. Option A is wrong because chlorofluorocarbons were covered by the original protocol of 1987 and their production has already been phased out under it. Option C is wrong because sulphur dioxide, the main cause of acid rain, is controlled by national air quality laws and emission standards, not by this treaty. Option D is wrong because methyl bromide, used to fumigate soil, is also part of the original list of ozone depleting substances. The point being tested is that Kigali deals with a climate gas through an ozone treaty.
The International Day for the Preservation of the Ozone Layer is observed on
- A.5 June
- B.22 April
- C.16 September
- D.2 December
Show answer
Correct answer: C. 16 September
Explanation
The correct answer is C, 16 September. The day marks the signing of the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987 and is observed every year with a theme announced by the United Nations. Option A is wrong because the fifth of June is World Environment Day, which marks the opening of the Stockholm Conference of 1972. Option B is wrong because the twenty second of April is Earth Day. Option D is wrong because the second of December is observed in India as National Pollution Control Day, in memory of the Bhopal gas tragedy of 1984. Environment sections regularly place these four dates in one question, so learn them as a set along with the twenty second of May for biological diversity and the second of February for wetlands.
The term marble cancer refers to
- A.The corrosion of marble monuments by acidic pollutants
- B.A disease of quarry workers who cut marble
- C.The growth of algae on marble floors
- D.The cracking of marble by extremes of temperature
Show answer
Correct answer: A. The corrosion of marble monuments by acidic pollutants
Explanation
The correct answer is A. Marble is calcium carbonate, and sulphur dioxide in polluted air, along with the sulphuric acid of acid rain, reacts with it to form calcium sulphate, so the stone loses its shine, turns yellow and becomes pitted and flaky. This damage is called marble cancer, and it is discussed most often in connection with the Taj Mahal at Agra, which is why industries around it are regulated. Option B is wrong because the lung disease caused by inhaling stone dust is silicosis, a different subject altogether. Option C is wrong because algal growth is a biological stain that can be cleaned and is not what the term means. Option D is wrong because thermal cracking is a physical weathering process common to many rocks and has nothing to do with pollution. Remember that any monument of marble or limestone is vulnerable, since both are calcium carbonate.