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Land & Agriculture

Soil, crops & sustainable farming

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Soil Composition

Soil = four components:

Mineral particles: Sand (large), silt (medium), clay (tiny). Affect drainage & texture.

Organic content: Dead plants/animals, bacteria, fungi. Provides nutrients.

Water: In pore spaces. Plants absorb it.

Gases: Air in pores. Roots need oxygen.

Balance all four = healthy soil.

Why Loam is Best

Loam = ideal blend of sand + silt + clay

Good drainage: Excess water drains (unlike clay)

Retains moisture: Enough water for plant roots (unlike sand)

Nutrient-rich: High organic content & inorganic ions (N, P, K)

Easy to work: Not too hard, not too sticky

Loam = farmer's dream soil.

Conditions for Crop Growth

Optimal factors:

Growing season: Long = more harvests (tropical > temperate)

Weather: Warm + adequate rain (not drought or flooding)

Daylight hours: Photosynthesis needs light

Soil pH: Most crops prefer neutral to slightly acidic

Soil nutrients: Nitrogen (growth), phosphorus (roots), potassium (flowers/fruit)

Wet seasons & dry seasons disrupt growth in tropical regions.

Types of Agriculture

Arable: Crops only (wheat, rice, maize)

Pastoral: Livestock only (cattle, sheep, goats)

Mixed: Both crops AND livestock — more sustainable

Subsistence: Farmer feeds own family (Low-income countries)

Commercial: Sell for profit (High-income countries)

Intensive: High inputs (fertilizer, pesticides, machinery) = high yield, low sustainability

Monoculture: One crop every season = efficient but risky (pests, diseases)

12 Strategies to Increase Yield

Crop practices:

• Crop rotation, intercropping, mixed cropping
• Drip irrigation, rainwater harvesting
• Mechanisation (tractors, harvesters)
• GMO crops (pest-resistant, drought-tolerant)

Growing environment:

• Greenhouses, hydroponics, aeroponics
• Managed grazing (rotate livestock)
• Urban farming, agroforestry

Fertilizers & pests:

• Organic (manure, mulch) & inorganic (NPK) fertilizers
• Chemical (pesticides, herbicides) & biological pest control

Impacts of Unsustainable Farming

Overproduction: Food waste. Spoilage if no cold storage.

Cash crops: Coffee, cotton, soya, palm oil REPLACE food crops — local hunger.

Irrigation mismanagement: Soil erosion, salinisation (salt buildup), waterlogging

Pesticide overuse: Pest resistance, resurgence, kills bees & pollinators

Fertilizer leaching: Nitrates runoff → eutrophication (algal blooms, dead zones)

Monoculture: Soil depleted, biodiversity lost, water/land pollution

Eutrophication Explained

Step-by-step process:

1. Excess nitrates/phosphates from fertilizer leach into water

2. Algae & aquatic plants overgrow (nutrient enrichment)

3. Plants die, bacteria decompose them (using oxygen)

4. Oxygen depletes → hypoxia (dead zone)

5. Fish & aquatic life suffocate & die

Result: From fertile to dead in months.

Soil Erosion: Causes

Unsustainable practices: Bare soil left exposed, overcultivation

Deforestation: No tree roots to bind soil. Surface runoff accelerates erosion.

Steep slopes: Gravity pulls topsoil downhill

Water erosion: Heavy rain washes soil away

Wind erosion: Dry areas, loose soil = dust blown away

Topsoil takes 100 years to form, minutes to lose.

Impacts of Soil Erosion

Silting: Eroded soil clogs rivers, reduces water supply & fish habitat

Desertification: Once-fertile land becomes desert (Sahel, Middle East)

Mass movement: Landslides, mudslides on unstable slopes

Crop failure: Loss of nutrient-rich topsoil → malnutrition & famine

Forced migration: People flee eroded lands → refugees

Mostly affects developing countries & marginal land.

Erosion Strategies: Part 1

Terracing: Cut horizontal steps on slopes. Reduces runoff & soil movement. Labor-intensive.

Contour ploughing: Plow in curves following slope, not straight down. Slows water runoff.

Bunds: Low walls between fields. Reduce runoff, wind speed, erosion. Also store water.

All three work by SLOWING WATER and TRAPPING SOIL.

Erosion Strategies: Part 2

Windbreaks: Trees/shrubs along field edges. Reduce wind speed & wind erosion. Also provide habitat.

Maintain vegetation: Grass, hedges, forest roots BIND soil. Prevent surface runoff. Absorb water.

Add organic matter: Compost, manure improve soil structure. Better water retention, less compaction.

The key: Keep soil COVERED, ROOTED, and MOIST.

Benefits & Limitations of Erosion Control

Benefits: Protect topsoil, increase yields long-term, reduce flooding, improve water quality

Limitations: High upfront cost, labor-intensive, requires farmer education, slow to show results

Often combined: Terraces + windbreaks + compost = maximum protection.

Summary: Sustainable Land Use

Soil health = crop success

✓ Maintain loam balance
✓ Rotate crops, reduce pesticides
✓ Use organic fertilizers
✓ Prevent erosion with vegetation & structures
✓ Avoid monoculture & overgrazing
✓ Respect seasonal rainfall patterns

Unsustainable farming depletes soil in decades.
Sustainable farming feeds generations.