The C:N ratio represents the proportion of carbon mass to nitrogen mass in organic matter. For well-decomposed Farmyard Manure, this ratio is typically 40:1. This balance is critical for microbial activity during decomposition; a ratio that is too high can immobilize nitrogen, while a ratio that is too low may lead to rapid nitrogen loss through volatilization or leaching, affecting overall soil fertility management.

The International Day of Forests is observed globally on March 21st. This day was established to celebrate and raise awareness about the importance of all types of forests and trees outside forests. It encourages countries to undertake local, national, and international efforts to organize activities involving forests and trees, such as tree-planting campaigns to combat deforestation.

Mycorrhizae represent a mutually beneficial symbiotic relationship between specialized fungi and plant roots. The fungi colonize the root system, extending the surface area for nutrient and water absorption, particularly phosphorus, while the plant provides the fungi with carbohydrates produced through photosynthesis. This association is crucial for plant health in many natural and agricultural ecosystems.

A normal solution is defined as a solution containing one gram equivalent weight of a solute per litre of solution. While the provided answer is D, note that in standard chemistry, one gram molecular weight per litre is typically defined as a molar solution (1 M). This discrepancy suggests a potential conflict in terminology usage within the source material regarding normal versus molar concentrations.

The total area of salt-affected soils in Pakistan is widely cited in agricultural literature as approximately 6.3 million hectares. Soil salinity is a major constraint to agricultural productivity in the region, affecting crop yields and land usability. Management of these soils through reclamation techniques is a critical focus for sustainable agriculture in the country.

Hygroscopic water exists as a thin film around soil particles, held by strong adhesive forces. Because the energy required by the plant to extract this water exceeds the suction force the plant roots can exert, it is considered unavailable for physiological processes. In contrast, capillary water is held in the pore spaces and is the primary source of water for plant growth.

In geological classification, rocks are categorized based on their silica content. Rocks containing more than 20% free quartz (silicon dioxide) are classified as acidic because they are rich in silica. These rocks, such as granite, typically have a higher resistance to weathering compared to basic rocks, which have lower silica content and higher concentrations of magnesium and iron.

Establishing wildlife sanctuaries is highly effective for conservation because it protects flora and fauna within their natural habitats. Unlike zoos, which are ex-situ conservation methods, sanctuaries provide an in-situ environment where species can thrive, breed, and interact naturally. The Wild Life (Protection) Act of 1972 in India formalizes this approach, ensuring that protected areas are managed to preserve biodiversity and support scientific research.

Lime (calcium carbonate) is often used in soil management to improve structure and displace sodium ions in sodic soils. While gypsum is more commonly used for direct salinity/sodicity reclamation, lime is applied to adjust pH and improve calcium levels. Note: The effectiveness of lime depends heavily on the specific soil chemistry, particularly the presence of exchangeable sodium versus soluble salts.

Peat soil is characterized by a high concentration of organic matter, typically exceeding 50% of its dry weight. This soil type forms in waterlogged conditions where decomposition is slow, leading to the accumulation of partially decayed plant material over long periods.