soil

What are the main soil horizons and what do they represent?

O: Organic matter, A: Topsoil, B: Subsoil, C: Weathered parent material.

What is the rock cycle?

A continuous process where rocks change between igneous, sedimentary, and metamorphic types through weathering, erosion, heat, and pressure.

What is mechanical weathering?

Physical breakdown of rocks (e.g., freezing, wind).

What is chemical weathering?

Chemical changes that break down rocks (e.g., acid rain, oxidation).

What are the three main soil textures?

Sand, silt, clay.

How does porosity affect soil?

Porosity is the amount of pore space which affects water and air storage.

How does permeability affect soil?

Permeability is the ability of soil to transmit water, affecting drainage.

What is organic matter and why is it beneficial?

Decomposed plant and animal material that improves soil structure, fertility, and water retention.

What are the primary nutrients for plants?

Nitrogen (N), Phosphorus (P), Potassium (K).

What are secondary nutrients?

Calcium (Ca), Magnesium (Mg), Sulfur (S).

What are micronutrients?

Iron (Fe), Manganese (Mn), Zinc (Zn), Copper (Cu), Boron (B), Molybdenum (Mo).

Why is soil pH important?

It affects nutrient availability; some nutrients become locked in very acidic or alkaline soils.

Why is nitrogen needed for plants?

Nitrogen is essential for chlorophyll production in chloroplasts, which is needed for photosynthesis.

What are the trophic levels in soil?

Producers: Plants, Primary consumers: Earthworms, Secondary consumers: Predatory insects, Decomposers: Bacteria.

What does compost supply to soil?

Organic matter and microbial diversity.

What is humus and how is it created?

Dark, nutrient-rich organic matter formed from decomposed plant and animal material in compost.

What are the main causes of soil erosion?

Wind, Water, Agriculture and construction.

How is irrigation water different from rainwater?

Irrigation water often contains dissolved salts, while rainwater is naturally low in salts.

What are the major cations involved in salinization?

Sodium (Na⁺), Calcium (Ca²⁺), Magnesium (Mg²⁺), Potassium (K⁺).

What is desertification?

Degradation of fertile land into desert, often due to overgrazing, deforestation, or poor irrigation.

What are the pros and cons of flood irrigation?

Easy, cheap; wastes water, can cause salinization.

What are the pros and cons of furrow irrigation?

Moderate efficiency; labor-intensive.

What are the pros and cons of sprinkle irrigation?

Even water distribution; can be costly, wind affects efficiency.

What are the pros and cons of drip irrigation?

Very water-efficient; expensive installation.

What is soil carbon sequestration?

The process of capturing carbon dioxide from the atmosphere and storing it in soil as organic carbon.

How can soil carbon sequestration be increased?

Adding compost, reduced tillage, agroforestry, crop rotation.