Question

Choose two factors that affect soil formation and describe each one.

Answer 1

Two important factors are climate and parent material.

- Climate
- What it is: Long-term patterns of temperature and precipitation at a site.
- How it affects soil: Temperature controls rates of chemical and biological reactions (weathering and decomposition); precipitation governs water availability, leaching of soluble ions, and profile development.
- Resulting differences: Humid, warm climates accelerate weathering and organic matter decomposition, often producing deep, leached, acidic soils (e.g., oxisols). Arid climates limit leaching and decomposition, producing shallow, salt- or carbonate-accumulating soils (e.g., aridisols).

- Parent material
- What it is: The original mineral or organic material from which the soil develops (bedrock, glacial till, alluvium, volcanic ash, etc.).
- How it affects soil: Determines initial texture, mineral composition, drainage, and nutrient supply, which influence how readily minerals weather and what nutrients are available to plants.
- Resulting differences: Soils from volcanic ash (Andisols) are often fertile and well-drained; soils from limestone-rich parent rock tend to be calcareous and higher pH; fine-grained clayey parent materials produce slow-draining, clay-rich soils.

You can see how these factors interact (e.g., a humid climate on quartz-rich sand yields very different soils than the same climate on nutrient-rich basalt).