The question asks about the common deficiencies in alluvial soils regarding plant nutrients. Alluvial soils are highly fertile but have specific nutrient limitations. We need to identify the combination of nutrients that are generally lacking in these soils.
C) Nitrogen, phosphorus and humus
This option correctly identifies the three most common deficiencies in alluvial soils. Nitrogen is almost always deficient, phosphorus availability is often low, and humus content can vary but is generally insufficient for sustained fertility without external additions, especially in intensively cultivated areas.
The question asks to identify the crop that is NOT typically associated with alluvial soils. Alluvial soils are highly fertile and are found extensively in the Indo-Gangetic plains. We need to evaluate the suitability of each crop mentioned in the options for alluvial soils.
Correct Option: C) Cotton is primarily associated with black soils (Regur soils) due to their high clay content and moisture retention capabilities, which are ideal for cotton cultivation. While it can be grown in other soil types, it is not typically or predominantly associated with alluvial soils as much as the other crops listed.
The question asks about the typical color range of alluvial soil. Alluvial soils are formed by the deposition of sediments by rivers, and their color is influenced by their composition, age, and moisture content.
Correct Option: A) Light grey to ash grey. This range accurately describes the typical color of alluvial soils, which are generally light-colored due to their formation process and composition.
The question asks for a local name for the black soil found in India. This requires knowledge of the different types of soils in India and their regional nomenclature.
Correct Option: C) Regur. Black soil is also widely known as 'Regur soil'. This name is derived from the Telugu word 'Reguda' and is commonly used in parts of Southern India, particularly in the Deccan Trap region where black soil is abundant. It is also called 'Black Cotton Soil' due to its suitability for cotton cultivation.
The question asks about the origin of black soils in India. We need to identify the parent rock material whose weathering leads to the formation of black soils. This requires knowledge of Indian geology and soil types.
D) Basaltic lava of the Deccan Trap — Black soils (Regur soils) are primarily formed from the weathering of basaltic lava rocks, which are abundant in the Deccan Trap region of India. The high iron and magnesium content in basalt contributes to the dark color and clayey texture of these soils.
The question asks about the primary reason for the dark color of black soils. This is a factual question related to soil composition and characteristics, often covered in geography and environmental science for competitive exams.
D) Titaniferous magnetite and organic matter
Black soils derive their characteristic dark color primarily from the presence of titaniferous magnetite, a mineral rich in iron and titanium, and a high content of organic matter (humus). The decomposition of organic material leads to the formation of dark-colored humus, while titaniferous magnetite directly contributes a black pigment.