Soil Types of India — Set 13

Correct Answer: B. Biological nitrogen fixation by legume crops and free-living bacteria

In alluvial soils of the Indo-Gangetic plains, biological nitrogen fixation is the primary natural source of nitrogen. Legume crops like pulses (chickpea, lentil, pigeon pea) host nitrogen-fixing Rhizobium bacteria in their root nodules. Free-living nitrogen-fixing bacteria like Azotobacter and Azospirillum also contribute. Growing legumes in rotation with cereals is a traditional method of maintaining soil nitrogen in alluvial soil regions.

Correct Answer: B. Pradhan Mantri Krishi Sinchayee Yojana - Watershed Development

The Pradhan Mantri Krishi Sinchayee Yojana - Watershed Development component focuses on the development of degraded and rainfed agricultural lands through watershed management. It funds construction of check dams, contour bunds, farm ponds, and vegetative measures to conserve soil and water. Integrated Watershed Management Projects (IWMP) are implemented in degraded, erosion-prone areas across India. The programme aims to restore productivity and increase water availability in water-scarce regions.

Correct Answer: B. Calcium makes the soil alkaline, improves soil structure, and is essential for cell wall formation in plants

Calcium is one of the most abundant nutrients in Black soil, contributing to its neutral to slightly alkaline pH. Calcium improves soil structure by flocculating clay particles, reducing stickiness and improving tilth. It is essential for plant cell wall formation, root elongation, and fruit quality. The high calcium content of Black soil is beneficial for most crops except those requiring acidic conditions.

Correct Answer: C. Waterlogging and high organic acidity

Peaty/Marshy soil presents challenges for agriculture due to waterlogging and high organic acidity. The waterlogged conditions exclude oxygen from the root zone, causing anaerobic conditions that are harmful to most crop plants. The decomposing organic matter produces organic acids (humic and fulvic acids), making the soil acidic. Drainage and liming are required to convert peaty soils into productive agricultural land.

Correct Answer: B. It increases water and nutrient retention and improves soil structure

Adding organic matter such as compost or farmyard manure to sandy soil significantly improves its water and nutrient-holding capacity. Organic matter particles occupy pore spaces and hold water by absorption, counteracting the quick drainage of sandy soil. It also supplies macro and micro nutrients that sandy soils naturally lack. Regular organic matter addition transforms sandy soil into a more productive medium capable of supporting a wider range of crops.

Correct Answer: B. Non-agricultural (urban, industrial) purposes

The National Land Use Policy aims to prevent or regulate the conversion of prime agricultural land to non-agricultural uses such as urban development, industrial zones, and infrastructure. India is losing significant areas of fertile alluvial and Black soil to urbanization and industrialization. Protecting agricultural land is essential for long-term food security. The policy advocates for spatial planning that directs development to wasteland or degraded land rather than productive farmland.

Correct Answer: C. Zinc

Zinc is a micro-nutrient (needed in very small quantities) that is essential for many plant enzyme functions, protein synthesis, and growth regulation. Zinc deficiency is the most widespread micro-nutrient deficiency in Indian soils and crops. It causes stunted growth, delayed maturity, and reduced yields in rice, wheat, and maize. Zinc sulphate is commonly applied to deficient soils, especially alluvial soils of the Indo-Gangetic plains.

Correct Answer: B. Sandy desert soil

Sandy desert soil is most susceptible to wind erosion because sand particles are large and light enough to be picked up and transported by wind. The lack of vegetation cover and moisture in desert soils means there is nothing to bind the sand particles together. The Thar Desert of Rajasthan experiences severe wind erosion, leading to sand dune formation and desertification. Shelter belt planting and sand stabilization techniques are used to control wind erosion.

Correct Answer: C. The organic litter horizon at the soil surface containing fresh and decomposing plant matter

The O horizon (Organic horizon) is the topmost layer of the soil profile and contains freshly fallen and partially decomposed organic material such as leaves, twigs, and animal matter. In forest soils, the O horizon is well-developed due to continuous leaf litter accumulation. In cultivated soils, the O horizon is often absent or minimal because crop residues are removed or ploughed in. The O horizon is critical for nutrient cycling and soil biodiversity.

Correct Answer: B. No-till or minimum tillage farming

No-till or minimum tillage farming is a conservation agriculture practice that reduces soil erosion by leaving the soil undisturbed between crops. The soil surface is protected by crop residues, which reduce the impact of rain, slow down runoff, and prevent wind erosion. Reduced tillage also preserves soil structure, organic matter, and microbial communities. Conservation tillage is increasingly promoted in India as a means of sustainable soil management and reducing input costs.