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RBSE SS Env Sci practice questions

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Question 1Environment: Concepts, Components and Ecosystem Structure

In ecosystem ecology, which term refers to the non-living physical and chemical components such as sunlight, temperature, water and minerals that influence organisms?

  1. Abiotic components Correct answer.
  2. Trophic levels
  3. Biotic components
  4. Decomposer guilds

Explanation

Abiotic components are the non-living features of an ecosystem, including climatic factors like sunlight and temperature and edaphic factors like soil minerals and water. They set the physical and chemical template within which organisms interact.

Question 2Environment: Concepts, Components and Ecosystem Structure

Which of the following best describes the role of producers in an ecosystem?

  1. They consume primary consumers and release stored energy as heat
  2. They transfer pathogens between trophic levels
  3. They convert inorganic substances into organic matter using an energy source such as sunlight Correct answer.
  4. They break down dead organic matter into inorganic nutrients

Explanation

Producers, mainly photosynthetic plants and algae, fix inorganic carbon into organic compounds using light energy, forming the base of the food web. This autotrophic process introduces energy and organic matter into the ecosystem.

Question 3Environment: Concepts, Components and Ecosystem Structure

A student draws a food chain: grass → grasshopper → frog → snake. Which organism occupies the third trophic level?

  1. Grass
  2. Snake
  3. Frog Correct answer.
  4. Grasshopper

Explanation

Trophic levels are counted from the producer, which is level one. Grass is level one, grasshopper level two, and the frog that eats the grasshopper sits at the third trophic level.

Question 4Environment: Concepts, Components and Ecosystem Structure

Which term describes the total mass of living organic matter present in a given area at a given time?

  1. Standing crop
  2. Biomass Correct answer.
  3. Net primary productivity
  4. Ecological efficiency

Explanation

Biomass is the mass of living organic material in a defined area at a defined time. It is usually expressed as dry weight per unit area and includes producers and consumers.

Question 5Environment: Concepts, Components and Ecosystem Structure

Which of these organisms is best classified as a decomposer?

  1. A mushroom-forming fungus on fallen leaves Correct answer.
  2. A hawk hunting rodents
  3. A fern growing on a forest floor
  4. A cyanobacterium in a pond

Explanation

Decomposers break down dead organic material and release inorganic nutrients back to the environment. Fungi such as mushrooms are classic decomposers, alongside many bacteria.

Question 6Environment: Concepts, Components and Ecosystem Structure

Which statement correctly distinguishes a habitat from an ecological niche?

  1. A habitat refers only to climate, while a niche refers only to soil type
  2. A habitat is the physical place where an organism lives, while a niche is its functional role and resource use Correct answer.
  3. A habitat is the functional role of an organism, while a niche is the physical place where it lives
  4. A habitat and a niche are identical concepts in modern ecology

Explanation

A habitat is the physical address of an organism, the place where it lives. A niche is its occupation, meaning the range of resources, conditions and interactions it uses, including its role in the community.

Question 7Environment: Concepts, Components and Ecosystem Structure

In a grassland, a herd of grazing herbivores is removed. Which change is the most direct expected consequence for the plant community?

  1. Soil decomposer populations will immediately disappear
  2. Grass biomass may increase because grazing pressure is reduced Correct answer.
  3. Photosynthetic rate will fall to zero
  4. The grassland will convert to a climax forest within one season

Explanation

Herbivores remove plant biomass through grazing, so removing them reduces that loss and can allow plant biomass to accumulate. The response is mediated by competition and resource availability, but the direct effect is reduced grazing pressure.

Question 8Environment: Concepts, Components and Ecosystem Structure

A food web contains many interconnected chains, while a food chain shows a single linear path. Why is a food web considered a more realistic representation of feeding relationships?

  1. Most consumers feed on several species and are eaten by several predators, creating multiple pathways Correct answer.
  2. Food webs exclude decomposers, which simplifies the diagram
  3. Food chains include energy losses that food webs ignore
  4. Food webs show only the largest predator in the community

Explanation

Real communities contain omnivores and generalist predators, so energy flows along many intersecting pathways rather than one line. A food web captures this complexity and shows alternative routes for energy and matter.

Question 9Environment: Concepts, Components and Ecosystem Structure

In a lake, phytoplankton fix 5,000 units of energy as gross primary production and respire 2,000 units. What is the net primary production?

  1. 5,000 units
  2. 3,000 units Correct answer.
  3. 2,000 units
  4. 7,000 units

Explanation

Net primary production equals gross primary production minus the energy used in plant respiration. Here 5,000 minus 2,000 gives 3,000 units, which is the energy stored as new plant biomass.

Question 10Environment: Concepts, Components and Ecosystem Structure

Approximately what proportion of energy is typically transferred from one trophic level to the next in a terrestrial ecosystem?

  1. About 10 percent Correct answer.
  2. About 50 percent
  3. About 1 percent
  4. About 90 percent

Explanation

Most energy is lost as heat through respiration and in unassimilated material, so only around 10 percent passes to the next trophic level. This low ecological efficiency explains why food chains rarely have more than four or five levels.

Question 11Environment: Concepts, Components and Ecosystem Structure

Why does a pyramid of energy always have a broad base and narrow top, even when a pyramid of numbers does not?

  1. Numbers of organisms always decrease at higher levels
  2. Energy increases at higher levels because predators are larger
  3. Energy decreases at each transfer because of respiration and heat loss, so higher levels hold less energy Correct answer.
  4. Decomposers add energy at the top of the pyramid

Explanation

The second law of thermodynamics means each transfer dissipates energy as heat, so the energy available at successive levels must decline. A pyramid of numbers can be inverted, for example when one tree supports many insects, but an energy pyramid cannot be.

Question 12Environment: Concepts, Components and Ecosystem Structure

Nitrogen-fixing bacteria in root nodules of legumes convert atmospheric nitrogen into a form plants can use. Which category of ecosystem component do these bacteria represent?

  1. Primary producer generating biomass
  2. Apex predator regulating populations
  3. Abiotic component supplying minerals
  4. Biotic component performing nutrient cycling Correct answer.

Explanation

The bacteria are living organisms, so they are a biotic component, and they perform a specific role in the nitrogen cycle by making nitrogen available to plants. Nutrient cycling links the biotic and abiotic parts of the ecosystem.

Question 13Environment: Concepts, Components and Ecosystem Structure

In the carbon cycle, which process returns carbon dioxide to the atmosphere from living organisms?

  1. Transpiration
  2. Cellular respiration Correct answer.
  3. Nitrogen fixation
  4. Photosynthesis

Explanation

Cellular respiration oxidises organic carbon and releases carbon dioxide to the atmosphere. Photosynthesis does the reverse, taking carbon dioxide into organic matter.

Question 14Environment: Concepts, Components and Ecosystem Structure

Two species of warbler feed in the same tree but forage in different parts of the canopy. This is best described as resource partitioning that reduces which interaction?

  1. Mutualism
  2. Predation
  3. Parasitism
  4. Interspecific competition Correct answer.

Explanation

When species that could compete for the same resource divide it by using different microhabitats, they reduce interspecific competition. This niche differentiation allows coexistence within the same habitat.

Question 15Environment: Concepts, Components and Ecosystem Structure

In a mutualistic relationship, how do the two species involved typically benefit?

  1. Both species are harmed by the association
  2. Each species gains a benefit such as nutrients, protection or pollination from the other Correct answer.
  3. One species benefits while the other is harmed
  4. One species benefits while the other is unaffected

Explanation

Mutualism is a positive interaction for both partners, for example a plant receiving pollination while a pollinator receives nectar. Each partner gains a resource or service that improves its fitness.

Question 16Environment: Concepts, Components and Ecosystem Structure

A keystone predator is removed from a rocky shore community, and mussels rapidly cover the rock surface. Which ecological concept does this illustrate?

  1. Bottom-up control driven by nutrient supply
  2. Top-down control of community structure by a keystone species Correct answer.
  3. Primary succession on bare rock
  4. Competitive exclusion by the keystone predator

Explanation

A keystone predator exerts influence disproportionate to its abundance by controlling a dominant competitor. Removing it releases mussels from predation, and they monopolise space, showing top-down regulation of community structure.

Question 17Environment: Concepts, Components and Ecosystem Structure

In primary succession on a bare volcanic substrate, which group typically establishes first and helps create conditions for later species?

  1. Pioneer species such as lichens and mosses Correct answer.
  2. Large grazing mammals
  3. Climax forest trees
  4. Apex predators

Explanation

Pioneer species can tolerate harsh conditions and begin soil formation by weathering rock and adding organic matter. Their activity makes the substrate suitable for later successional species.

Question 18Environment: Concepts, Components and Ecosystem Structure

An ecologist measures that a pond's producers fix 20,000 kcal, primary consumers assimilate 2,000 kcal, and secondary consumers assimilate 200 kcal. What is the ecological efficiency of transfer from producers to primary consumers?

  1. 90 percent
  2. 20 percent
  3. 1 percent
  4. 10 percent Correct answer.

Explanation

Transfer efficiency is assimilation at the higher level divided by the energy at the lower level, here 2,000 divided by 20,000, which equals 10 percent. This matches the commonly cited order-of-magnitude efficiency between trophic levels.

Question 19Environment: Concepts, Components and Ecosystem Structure

In a detritus-based food web of a forest floor, leaf litter supports bacteria, fungi, detritivores and their predators. Which statement best explains why this web is essential to long-term ecosystem function?

  1. Leaf litter is the main source of solar energy for the forest
  2. Predators of detritivores fix atmospheric nitrogen
  3. Decomposition releases inorganic nutrients that producers need to sustain primary production Correct answer.
  4. Detritivores directly photosynthesise and add new carbon to the system

Explanation

Detrital webs mineralise organic matter, returning nitrogen, phosphorus and other nutrients to the soil where producers can take them up. Without this recycling, nutrient stocks would become locked in dead matter and primary production would decline.

Question 20Environment: Concepts, Components and Ecosystem Structure

Two species with identical niches are introduced into the same closed habitat. According to the competitive exclusion principle, what is the most likely long-term outcome?

  1. One species will exclude the other from the shared resource Correct answer.
  2. Both species will coexist indefinitely at equal abundance
  3. Predation will always prevent competition
  4. They will merge into a single hybrid species

Explanation

The competitive exclusion principle states that two species cannot coexist indefinitely on the same limiting resource if their niches are identical. One will outcompete the other unless niche differentiation or other factors intervene.

Question 21Natural Resources: Land, Soil, Water, Energy and Forests

In the standard classification of land capability, what does a Class VIII designation indicate?

  1. Land with severe limitations that restrict use to recreation, wildlife, or watershed protection Correct answer.
  2. Land suited to grazing but not to cultivated crops
  3. Land that can support forestry but not annual crops
  4. Land suitable for intensive cultivation with only minor conservation practices

Explanation

Land capability classes run from I to VIII, and the highest-numbered class carries the most severe limitations. Class VIII land is not suitable for commercial plant production and is restricted to uses such as wildlife habitat, recreation, or watershed protection. Classes II and III describe cultivable land with increasing conservation needs, while classes VI and VII are generally suited to grazing or forestry.

Question 22Natural Resources: Land, Soil, Water, Energy and Forests

Which soil erosion process involves the removal of a thin, fairly uniform layer of topsoil across a slope by raindrop impact and sheet flow?

  1. Gully erosion
  2. Sheet erosion Correct answer.
  3. Rill erosion
  4. Splash erosion

Explanation

Sheet erosion removes soil in thin, relatively uniform layers as surface water flows across a slope without concentrating. Rills and gullies form only after flow concentrates into channels, and splash erosion refers to the initial detachment of particles by raindrop impact. Sheet erosion often goes unnoticed because the surface appears largely intact while fertility is lost.

Question 23Natural Resources: Land, Soil, Water, Energy and Forests

A farmer wants to reduce erosion on a long, steep field by alternating strips of row crops with strips of dense grass along the contour. Which soil conservation practice does this describe?

  1. Terracing
  2. Mulching
  3. Contour bunding
  4. Strip cropping Correct answer.

Explanation

Strip cropping uses alternating bands of different crops, often including a close-growing cover, laid across the slope to slow runoff and trap soil. The grass strips act as filters that reduce the velocity of water moving downslope. Bunding and terracing modify the slope itself with earthworks, while mulching covers the soil surface without changing field layout.

Question 24Natural Resources: Land, Soil, Water, Energy and Forests

In a soil profile, which horizon is typically richest in accumulated organic matter and is most directly lost through erosion?

  1. B horizon
  2. C horizon
  3. R horizon
  4. A horizon Correct answer.

Explanation

The A horizon is the surface layer where organic matter accumulates and biological activity is greatest, making it the most fertile and most vulnerable to erosion. The B horizon is a subsoil zone of accumulation of clays and minerals, and the C horizon consists of weathered parent material. The R horizon is unweathered bedrock beneath the soil.

Question 25Natural Resources: Land, Soil, Water, Energy and Forests

Which soil property is most directly improved by adding organic matter such as compost or green manure?

  1. Soil pH buffering toward strong acidity
  2. Depth of the water table
  3. Water-holding capacity and aggregate stability Correct answer.
  4. Bulk density of the underlying bedrock

Explanation

Organic matter binds soil particles into stable aggregates and increases the pore space available for retaining water, improving both structure and moisture storage. It also feeds soil organisms that maintain aggregation. Organic amendments do not control bedrock properties or water-table depth, and their effect on pH is generally a mild buffering rather than a strong acidifying one.

Question 26Natural Resources: Land, Soil, Water, Energy and Forests

Salinization of irrigated farmland most commonly results from which combination of conditions?

  1. Deep ploughing that mixes subsoil with topsoil
  2. Heavy rainfall flushing salts downward through a sandy profile
  3. Application of nitrogen fertilizer without phosphorus
  4. Irrigation with slightly saline water combined with high evaporation and poor drainage Correct answer.

Explanation

Salinization occurs when dissolved salts in irrigation water are left behind as water evaporates, and poor drainage prevents them from being leached away. Arid and semi-arid climates with high evaporative demand are especially vulnerable. Adequate drainage and leaching with good-quality water are the standard remedies.

Question 27Natural Resources: Land, Soil, Water, Energy and Forests

Which practice best describes conservation tillage aimed at reducing soil loss?

  1. Flood irrigation immediately after harvest
  2. Leaving crop residue on the surface and minimizing soil disturbance Correct answer.
  3. Complete inversion of the topsoil with a mouldboard plough each season
  4. Removing all stubble for use as fuel

Explanation

Conservation tillage retains a cover of crop residue on the soil surface and limits the number and depth of tillage passes. The residue intercepts raindrop energy, slows runoff, and protects aggregates from breakdown. Removing residue or inverting the whole profile exposes soil to erosion.

Question 28Natural Resources: Land, Soil, Water, Energy and Forests

Which statement correctly distinguishes a renewable from a non-renewable resource in the context of energy?

  1. Non-renewable resources are those found underground, while renewable resources are found above ground
  2. Renewable resources always produce no emissions, while non-renewable resources always do
  3. Renewable resources are always cheaper per unit than non-renewable resources
  4. Renewable resources are replenished on human timescales, while non-renewable resources form over geological timescales Correct answer.

Explanation

The defining difference is the rate of replenishment relative to human use. Renewables such as solar, wind, and sustainably managed biomass are replenished continuously or within human lifetimes, whereas fossil fuels and nuclear ores accumulate over geological time. Cost and emissions are separate considerations that do not define renewability.

Question 29Natural Resources: Land, Soil, Water, Energy and Forests

Which energy source is classified as non-renewable because its fuel accumulates over geological time?

  1. Tidal energy
  2. Geothermal heat
  3. Coal Correct answer.
  4. Wind

Explanation

Coal forms from buried plant material over millions of years, so consumption outpaces replenishment and it is treated as non-renewable. Tidal, geothermal, and wind energy are driven by ongoing natural processes and are replenished continuously. The distinction rests on the timescale of replacement, not on the physical state of the resource.

Question 30Natural Resources: Land, Soil, Water, Energy and Forests

A community wants to reduce dependence on fossil fuels for electricity. Which option best represents a renewable, non-combustion generation source?

  1. Natural gas combined-cycle plant
  2. Diesel generator set
  3. Rooftop photovoltaic array Correct answer.
  4. Coal-fired thermal plant

Explanation

Photovoltaic panels convert sunlight directly into electricity without combustion and rely on a continuously replenished resource. Diesel, natural gas, and coal all release stored fossil carbon when burned. Among the listed options, only the photovoltaic array is both renewable and non-combustion.

Question 31Natural Resources: Land, Soil, Water, Energy and Forests

Which factor most strongly limits the practical use of solar photovoltaic generation in a region?

  1. Presence of forest cover on nearby hills
  2. Latitude, cloud cover, and hours of sunshine Correct answer.
  3. Thickness of the local soil profile
  4. Availability of groundwater for cooling

Explanation

Photovoltaic output depends on the amount of solar radiation reaching the panels, which is governed by latitude, seasonal sun angle, cloud cover, and daylight hours. Groundwater, soil depth, and hillside forest cover do not determine the solar resource. Siting and storage considerations follow from the irradiance profile.

Question 32Natural Resources: Land, Soil, Water, Energy and Forests

Which statement best describes the hydrological cycle's role in renewing freshwater supplies?

  1. Rainfall is generated mainly by the decomposition of soil organic matter
  2. Groundwater is created anew in aquifers each year by chemical reactions in bedrock
  3. Freshwater is produced when seawater freezes and is stored permanently in glaciers
  4. Evaporation from oceans and transpiration from plants return water vapour to the atmosphere, which condenses and falls as precipitation Correct answer.

Explanation

The hydrological cycle moves water from oceans, lakes, and vegetation into the atmosphere by evaporation and transpiration. Cooling at altitude condenses the vapour into clouds and precipitation, which replenishes surface and groundwater. This continuous circulation is what makes freshwater a renewable but finite resource.

Question 33Natural Resources: Land, Soil, Water, Energy and Forests

Which practice most directly promotes groundwater recharge in an urbanizing watershed?

  1. Paving all open ground to speed drainage
  2. Channelizing streams into concrete-lined drains
  3. Constructing recharge pits and permeable surfaces to let runoff infiltrate Correct answer.
  4. Extracting groundwater at a rate above natural recharge

Explanation

Recharge depends on water infiltrating through the soil to the saturated zone. Recharge pits, permeable paving, and infiltration basins increase the proportion of rainfall that enters the ground rather than running off. Impervious surfaces and concrete channels do the opposite, and over-extraction depletes storage.

Question 34Natural Resources: Land, Soil, Water, Energy and Forests

Which irrigation method generally achieves the highest water-use efficiency for a row crop by delivering water directly to the root zone?

  1. Sprinkler irrigation
  2. Flood irrigation
  3. Furrow irrigation
  4. Drip irrigation Correct answer.

Explanation

Drip or trickle irrigation delivers water slowly and directly to the root zone through emitters, minimizing evaporation and deep percolation losses. Flood and furrow systems wet large areas and lose water to evaporation and runoff, while sprinklers lose water to wind drift and evaporation. Drip systems are well suited to row crops and orchards where lines can be laid along the rows.

Question 35Natural Resources: Land, Soil, Water, Energy and Forests

Which of the following best characterizes a watershed as a management unit?

  1. A single aquifer with no surface connection
  2. A political boundary defined by municipal jurisdiction
  3. The area of land that drains to a common outlet Correct answer.
  4. A reserved forest block with fixed boundaries

Explanation

A watershed, or catchment, is the land area from which all precipitation drains to a common point such as a stream outlet or lake. Managing water, soil, and vegetation within this physical boundary aligns land use with downstream water quality. It is a hydrological rather than political or administrative unit.

Question 36Natural Resources: Land, Soil, Water, Energy and Forests

Which measure is most effective for controlling eutrophication in a lake receiving agricultural runoff?

  1. Stocking the lake with more algae
  2. Increasing fertilizer application on nearby fields
  3. Reducing nutrient inputs, especially phosphorus and nitrogen, from the catchment Correct answer.
  4. Deepening the lake by dredging to increase its volume

Explanation

Eutrophication is driven by excess nutrients, chiefly phosphorus in freshwater systems and nitrogen in coastal waters. Controlling the sources of these nutrients from farmland and settlements is the primary remedy. Dredging can remove stored nutrients but does not address ongoing inputs, and adding algae worsens the problem.

Question 37Natural Resources: Land, Soil, Water, Energy and Forests

Which statement about the role of forests in the water cycle is most accurate?

  1. Forests eliminate all runoff from a catchment
  2. Forest canopies and litter increase infiltration and reduce surface runoff while transpiring water to the atmosphere Correct answer.
  3. Forests have no measurable effect on local rainfall
  4. Forests increase soil erosion by exposing mineral soil

Explanation

Forest vegetation intercepts rainfall, and the litter layer and root networks improve infiltration and reduce overland flow. At the same time, trees transpire substantial quantities of water back to the atmosphere. Forests do not eliminate runoff, and by protecting soil they generally reduce erosion.

Question 38Natural Resources: Land, Soil, Water, Energy and Forests

Which forest management practice is most consistent with sustainable timber production?

  1. Removing all dead wood and leaf litter for fuel
  2. Converting forest land to annual cropping
  3. Clear-felling an entire catchment each year
  4. Selective harvesting with replanting and protection of regeneration Correct answer.

Explanation

Sustainable forestry harvests timber at a rate that allows regeneration and maintains the protective functions of the forest. Selective felling combined with replanting and protection of natural regeneration supports this balance. Clear-felling whole catchments, stripping litter, or converting forest to cropland degrades the resource base.

Question 39Natural Resources: Land, Soil, Water, Energy and Forests

In forest survey terminology, what does 'increment' refer to?

  1. The number of trees cut in a season
  2. The growth in volume or biomass of a stand over a defined period Correct answer.
  3. The total area of forest in a state
  4. The proportion of forest lost to fire

Explanation

Increment is the increase in tree or stand volume, biomass, or basal area over a specified period. It is used to set a sustainable annual allowable cut that does not exceed growth. Harvest counts, total forest area, and fire losses are different measures and do not describe growth.

Question 40Natural Resources: Land, Soil, Water, Energy and Forests

Which type of forest is most associated with the term 'biodiversity hotspot' in the context of conservation planning?

  1. A plantation of a single fast-growing species
  2. A naturally diverse forest with high endemism and significant habitat loss Correct answer.
  3. A grassland converted to Eucalyptus
  4. An urban park with ornamental trees

Explanation

A biodiversity hotspot is defined by exceptional species richness and endemism combined with substantial loss of original habitat. Naturally diverse forests meeting these criteria are priority conservation areas. Monoculture plantations, converted grasslands, and urban parks lack the endemism and natural habitat criteria.

Question 41Natural Resources: Land, Soil, Water, Energy and Forests

Which soil texture class generally has the highest water-holding capacity and cation exchange capacity?

  1. Gravel
  2. Coarse sand
  3. Clay Correct answer.
  4. Sandy loam

Explanation

Clay particles are very small and carry a high surface charge, giving them large specific surface area for water retention and cation exchange. Sandy and gravelly soils have large particles and low surface area, so they retain little water or nutrients. Clay soils can, however, suffer from poor drainage and compaction.

Question 42Natural Resources: Land, Soil, Water, Energy and Forests

A water resource manager observes that a river's dry-season flow has declined steadily over a decade while annual rainfall is unchanged. Which explanation is most plausible?

  1. A decrease in the river's channel capacity
  2. Loss of forest cover and wetland storage that previously released water slowly Correct answer.
  3. Reduced water demand from the town
  4. Increased groundwater recharge in the catchment

Explanation

Baseflow in the dry season depends on water stored and slowly released by soils, wetlands, and forested catchments. If that storage and cover are lost, more rainfall leaves as rapid runoff and less remains to sustain dry-season flow. Reduced demand would tend to raise flow, and channel capacity affects stage rather than the volume of baseflow.

Question 43Natural Resources: Land, Soil, Water, Energy and Forests

Which of the following best describes the purpose of a shelterbelt in land management?

  1. To reduce wind erosion and protect crops and soil by slowing wind near the surface Correct answer.
  2. To raise the water table beneath the field
  3. To increase wind speed across a field
  4. To increase soil salinity

Explanation

Shelterbelts are rows of trees or shrubs planted to reduce wind velocity near the ground, protecting soil from wind erosion and reducing crop damage and moisture loss. The reduced wind speed lowers the transport of soil particles. Shelterbelts do not raise the water table or increase salinity.

Question 44Natural Resources: Land, Soil, Water, Energy and Forests

In India's land-use classification, 'culturable waste land' refers to which category?

  1. Land occupied by buildings and roads
  2. Land that is permanently barren rock
  3. Land under permanent pasture only
  4. Land available for cultivation but not currently taken up, excluding fallow and current fallow Correct answer.

Explanation

Culturable waste land is land capable of cultivation that is not currently under crops and is distinct from current and other fallow. It may be overgrown with scrub or otherwise unused but retains agricultural potential. Built-up land and barren rock are separate categories.

Question 45Natural Resources: Land, Soil, Water, Energy and Forests

Which practice would most directly reduce the rate of soil organic carbon loss in a continuously cropped field?

  1. Repeated deep ploughing to aerate the soil
  2. Leaving the soil bare between seasons
  3. Burning crop residue after every harvest
  4. Retaining crop residue and incorporating organic amendments Correct answer.

Explanation

Organic carbon is lost when residue is removed or burned and when tillage exposes soil carbon to rapid oxidation. Retaining residue and adding compost or manure returns carbon to the soil and supports aggregation. Bare soil and repeated deep ploughing accelerate decomposition and erosion.

Question 46Natural Resources: Land, Soil, Water, Energy and Forests

In the Universal Soil Loss Equation (USLE), which factor represents the combined effect of rainfall and runoff in driving soil erosion?

  1. The soil erodibility factor
  2. The cover and management factor
  3. The rainfall erosivity factor Correct answer.
  4. The support practice factor

Explanation

The USLE multiplies several factors, and the rainfall erosivity term (R) quantifies the erosive force of rainfall and the runoff it generates at a site. It is the climatic driver of detachment, distinct from soil properties, land cover, and conservation structures.

Question 47Natural Resources: Land, Soil, Water, Energy and Forests

Which soil conservation measure is a physical barrier built across a slope to slow runoff and trap sediment before it reaches lower fields?

  1. Crop rotation
  2. Green manuring
  3. Contour bunding Correct answer.
  4. Mulching

Explanation

Contour bunding constructs small earthen embankments along the contour, interrupting the slope length so runoff velocity drops and sediment settles behind each bund. The other options are agronomic treatments that improve cover or fertility but do not create a physical barrier across the slope.

Question 48Natural Resources: Land, Soil, Water, Energy and Forests

A farmer on deep, well-drained sandy loam wants to reduce irrigation losses and apply fertilizer efficiently. Which irrigation method best matches these goals while limiting deep percolation and runoff?

  1. Drip irrigation with fertigation Correct answer.
  2. Furrow irrigation down long graded channels
  3. Flood irrigation of the whole field
  4. Overhead sprinkler irrigation at midday

Explanation

Drip irrigation delivers water slowly and directly to the root zone, so deep percolation and evaporation losses are minimized, and fertigation lets nutrients be applied with the water. On a deep sandy loam, where water drains quickly, this precision is especially valuable for keeping water and nutrients in the root zone.

Question 49Natural Resources: Land, Soil, Water, Energy and Forests

A hill state plans to expand agriculture onto steep, deforested slopes. Which combination of measures most directly protects the land from accelerated erosion while allowing cultivation?

  1. Complete abandonment of the slopes with no further use
  2. Removal of all crop residue to keep the surface clean
  3. Deep ploughing along the slope direction to improve drainage
  4. Bench terracing combined with contour-aligned vegetative strips Correct answer.

Explanation

Bench terracing converts a long steep slope into short, level steps that reduce slope length and runoff velocity, while vegetative strips along the contour trap sediment and reinforce the terraces. Together they allow cultivation on steep land while cutting the erosive energy that deforestation had exposed.

Question 50Natural Resources: Land, Soil, Water, Energy and Forests

A catchment authority compares two proposals for a degraded watershed: planting fast-growing exotics in pure stands, or restoring a mix of native species with protected regeneration. Which analysis best justifies the mixed-native restoration on sustainability grounds?

  1. Native species grow too slowly to be worth planting, so only exotics can restore cover
  2. Species choice has no bearing on watershed function, so the cheaper option should always be chosen
  3. Mixed native restoration better supports infiltration, soil stability, and habitat continuity, and poses lower invasive and water-use risk Correct answer.
  4. Pure exotic stands always yield more biomass per hectare, so they are preferable regardless of other effects

Explanation

A mixed native stand tends to develop deeper, more continuous root and litter layers that improve infiltration and soil stability, and it maintains habitat connectivity, whereas fast-growing exotics in pure stands can deplete soil water, acidify or degrade soils, and escape as invasives. Sustainability therefore favors weighing hydrological and ecological function, not biomass alone.