Match the following soil orders with their descriptions: a) Histosols i) Soil order that includes soils formed on volcanic ash b) Andisols ii) Soil order of cold regions including soils underlain by permafrost c) Gelisols iii) Soil order consisting of soils of dry climates d) Aridsols iv) Soil order consisting of soils with a thick upper layer of organic matter

🔑 Key Points
🌍 Soil Classification System
→ The recent system of Soil Classification used in India was developed in the U.S.A. and passed through various stages, with the last one being the 7th approximation (Soil Survey Staff, 1960).
→ It was later published as USDA Soil Taxonomy and has been modified several times, including an improvement in 1998 (Soil Survey Staff, 1998).

🌱 Types of Soils
1️⃣ Histosols
→ Histosols account for 10% of the land area.
→ These soils are mainly composed of organic materials.
→ The organic deposit ranges between 147-180 cm and organic carbon level between 32-54%.
→ 70% of Histosols occur in the frigid northern zone.

2️⃣ Andisols
→ Formed by the weathering products of volcanic rocks, Andisols store organic carbon at a significantly higher proportion compared to other soils.
→ They cover only 0.8% of the ice-free surface on Earth but sequester more than 1.8% of the global soil carbon stock.
→ Their higher carbon content is due to their relatively high content of poorly crystalline minerals.

3️⃣ Gelisols
→ Frost churning (cryoturbation) plays a critical role in the formation of Gelisols.
→ These soils are influenced by ground patterning, sequestration of organic matter below the soil surface, and alterations to the soil structure.
→ The Turbel suborder and Turbic subgroups are defined by cryoturbated horizons and gelic materials, including broken horizons, organic matter near or within the permafrost table, and oriented rock fragments.

4️⃣ Aridsols
→ Aridsols are soils found in dry regions.
→ These soils have a very low level of organic matter and lack vegetative production due to their dry nature.

📌 Important Points
→ Histosols

(i) Soil order consisting of soils with a thick upper layer of organic matter.
→ Andisols
(ii) Soil order that includes soils formed on volcanic ash.
→ Gelisols
(iii) Soil order of cold regions, including soils underlain by permafrost.
→ Aridsols
(iv) Soil order consisting of soils in dry climates.