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Soil as a Resource – Long Answer Questions

Medium Level (Application & Explanation)

Q1. Why is soil called a non-renewable resource, and how does its slow formation influence agricultural planning in India?

Answer:

  • Soil is called non-renewable because its formation is very slow, taking thousands of years to create just a few centimeters through weathering of rocks, organic matter decomposition, and climate action.
  • In India, this means agricultural planning must focus on soil conservation, balanced fertilization, and crop rotation to prevent soil degradation.
  • Farmers must protect topsoil from erosion using contour ploughing, terracing, and mulching.
  • Since fertile soil cannot be quickly replaced, practices like mixed farming, organic manure, and minimal tillage become essential.
  • Regions like the Indo-Gangetic plains rely on careful water management to sustain alluvial soils, while Deccan Plateau farmers manage the black soil’s water-heavy nature.
  • Overall, viewing soil as a finite resource pushes both farmers and policymakers to adopt sustainable agriculture to protect food security and maintain ecosystem balance.

Q2. Explain how the characteristics of alluvial soils support high agricultural productivity in the Indo-Gangetic plains.

Answer:

  • Alluvial soils are loamy, deep, and well-drained, making them highly fertile for diverse crops.
  • They are formed by river deposition (silt, sand, and clay), which regularly replenishes nutrients like potassium and phosphorus.
  • Their texture supports both good aeration and water retention, which is ideal for crops such as rice, wheat, sugarcane, and pulses.
  • Located in floodplains and deltas of the Ganga and Brahmaputra, these soils benefit from adequate irrigation and favorable climate.
  • Farmers practice multiple cropping due to the soils’ moisture-holding capacity and fine tilth.
  • To maintain productivity, they apply green manure, biofertilizers, and balanced NPK, and manage floods using embankments and drainage systems.
  • Thus, the physical and chemical properties of alluvial soils directly enable high yields and intensive agriculture.

Q3. Black soil swells when wet and cracks when dry. How do these properties affect farming practices in the Deccan Plateau?

Answer:

  • Black soil (regur), derived from basalt, has a high clay content and excellent water retention. It swells in the monsoon and cracks in summer.
  • These properties make it ideal for cotton, groundnut, and tobacco, which benefit from steady moisture.
  • However, swelling can cause waterlogging, so farmers use broad-bed and furrow systems, raised beds, and field drains.
  • The cracking in dry months improves aeration, but it can damage roots of perennials, so timely irrigation and mulching are used to reduce moisture loss.
  • Farmers prefer deep-rooted or drought-tolerant crops and adopt intercropping (e.g., cotton with pigeon pea) to manage moisture fluctuations.
  • Organic matter additions (farmyard manure, compost) help stabilize soil structure and improve porosity.
  • Thus, farming on black soils requires careful water management and crop planning to use its strengths and reduce risks.

Q4. Compare red and yellow soils with laterite soils in terms of formation, fertility, and crop suitability. How can their productivity be improved?

Answer:

  • Red and yellow soils form from crystalline rocks under heat and humidity. They are sandy to loamy, often low in nitrogen and humus, with iron giving the red color.
  • Laterite soils form under high rainfall and temperature, where leaching removes bases, leaving iron and aluminum oxides. They are porous and can harden on exposure.
  • Crops:
    • Red/yellow soils: groundnut, cotton, millets, rice (with irrigation).
    • Laterite soils: tea, coffee, cashew, and rubber in high rainfall zones.
  • Improvement methods:
    • Add organic matter (compost, green manure) to increase humus.
    • Apply lime where soils are acidic to improve nutrient availability.
    • Use balanced fertilizers (NPK) and micronutrients (e.g., zinc).
    • Adopt mulching and drip irrigation to reduce evaporation.
    • Prevent leaching with contour bunding and cover crops.
  • With these practices, both soil types can support productive and sustainable farming.

Q5. Describe how soil helps regulate the water cycle and supports biodiversity. Give examples from Indian contexts.

Answer:

  • Soil acts like a sponge, enabling infiltration, storage, and slow release of water to plants, streams, and aquifers.
  • Loamy soils in alluvial plains hold water for rice and wheat, while black soils retain moisture for cotton during dry spells.
  • Soil organisms—like earthworms, bacteria, and fungi—break down organic matter, recycle nutrients, and improve soil structure, supporting healthy roots and plant diversity.
  • Forest soils in the Western Ghats and Himalayas store water and reduce runoff, guarding against floods and landslides.
  • Diverse plant growth creates habitats for birds, insects, and pollinators, enhancing ecosystem services such as pollination and pest control.
  • Practices like mulching, agroforestry, and cover cropping help conserve soil moisture, promote microbial life, and maintain biodiversity.
  • Thus, soil is central to water regulation and ecosystem health, supporting agriculture and wildlife alike.

High Complexity (Analytical & Scenario-Based)

Q6. A river changes its course, reducing fresh alluvial deposits in a district. Analyze the impact on agriculture and suggest adaptive strategies.

Answer:

  • Reduced silt deposition means fewer natural nutrients, leading to declining yields of rice, wheat, and vegetables.
  • Groundwater recharge may drop, affecting irrigation and rabi crops. Soil may compact without new fine sediments.
  • Farmers can adapt by:
    • Introducing green manuring, farmyard manure, and biofertilizers to restore soil fertility.
    • Practicing crop rotation with legumes to fix nitrogen and improve soil structure.
    • Using micro-irrigation (drip/sprinkler) to save water and maintain soil moisture.
    • Building check dams, percolation tanks, and field bunds to enhance local recharge.
    • Shifting part of the area to horticulture or oilseeds that require less standing water.
    • Employing soil testing to apply balanced NPK and micronutrients.
  • With integrated measures, agriculture can remain viable despite river dynamics.

Q7. A farmer on the Deccan Plateau faces erratic monsoons on black soil. Design a cropping and soil management plan for climate resilience.

Answer:

  • Cropping plan:
    • Choose drought-tolerant and deep-rooted crops: cotton, pigeon pea, sorghum, soybean, and chickpea for rabi if moisture permits.
    • Use intercropping (cotton + pigeon pea) to stabilize income and use moisture efficiently.
    • Stagger sowing with short- and medium-duration varieties to hedge against late rains.
  • Soil and water management:
    • Adopt broad-bed and furrow layout to drain excess rain and store moisture in furrows.
    • Apply mulch and organic matter to reduce evaporation and improve structure.
    • Create farm ponds, check bunds, and contour trenches for in-situ water harvesting.
    • Use drip irrigation for cash crops; schedule irrigation based on soil moisture.
    • Conduct soil testing and apply balanced fertilizers with split doses to avoid loss.
  • This integrated approach builds climate resilience, stabilizes yields, and conserves soil health.

Q8. Evaluate the sustainability of using canal irrigation versus drip irrigation to reclaim arid soils for agriculture in Rajasthan.

Answer:

  • Canal irrigation can quickly expand area under crops like wheat and cotton, but high evaporation and poor drainage in arid soils may cause waterlogging and salinity.
  • It often leads to inefficient water use, especially on sandy, low-organic soils with high percolation losses.
  • Drip irrigation delivers water at the root zone, reducing evaporation, weeds, and salinity buildup by controlling soil moisture precisely.
  • Drip fits horticulture (e.g., pomegranate, date palm) and vegetables, gives higher water-use efficiency, and supports fertigation for targeted nutrition.
  • For long-term sustainability, drip plus mulching, windbreaks, organic amendments, and salt-tolerant varieties helps reclaim soils without degrading them.
  • Canals can still be useful if paired with lined channels, proper drainage, and conjunctive use with groundwater.
  • Overall, a drip-first strategy with soil conservation is more sustainable in arid Rajasthan.

Q9. How does deforestation in the Western Ghats alter forest soils and downstream agriculture, and what community actions can reduce the damage?

Answer:

  • Deforestation removes canopy cover and leaf litter, reducing organic matter and humus in forest soils.
  • Without roots, infiltration falls and runoff rises, causing erosion, landslides, and siltation in rivers.
  • Downstream, alluvial fields face flooding, sand deposition, and clogged canals, lowering crop yields and damaging **i...

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