Correct Option
The correct option is (b) 1 and 2 only.
Explanation
Soil fertility refers to the ability of soil to sustain plant growth by providing essential plant nutrients and favorable chemical, physical, and biological conditions. It is primarily determined by the composition of the soil, specifically the balance between mineral content and organic material.
Statement-wise Analysis
- Statement 1 is Correct: A right mix of minerals is fundamental to soil fertility. Minerals derived from the parent rock provide essential nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium, which are necessary for plant growth.
- Statement 2 is Correct: Organic matter (humus) is a critical component of fertile soil. It improves soil structure, enhances water-retention capacity, promotes aeration, and serves as a reservoir of nutrients released through decomposition.
- Statement 3 is Incorrect: While weathering is the process that forms soil, intense weathering does not necessarily lead to fertility. In fact, intense leaching caused by heavy rainfall and high temperatures (as seen in Laterite soils) often removes essential silica and bases (lime, magnesia), leaving behind iron and aluminum oxides, which results in low fertility. Furthermore, the word "only" makes the statement restrictive and factually wrong.
- Statement 4 is Incorrect: High altitude is not a prerequisite for soil fertility. Soils at high altitudes are often thin, immature, and prone to erosion due to steep slopes. Additionally, low temperatures at high altitudes slow down the decomposition of organic matter and chemical weathering, often limiting soil development. The most fertile soils (like alluvial soils) are typically found in plains and river valleys, not necessarily at high altitudes.
Key Takeaway: Soil fertility is primarily dependent on a balanced composition of mineral nutrients and organic matter (humus), along with appropriate texture and pH. Extreme weathering or high altitude often acts as a constraint rather than a facilitator of fertility.