jarðvegur

Jarðvegur, or soil, is the loose, weathered mineral and organic material on the Earth's surface that supports plant life. It consists of minerals derived from bedrock, organic matter from dead organisms, water, air, and living organisms such as bacteria, fungi, and earthworms. Soils vary widely in depth, fertility, structure, and moisture, yet they play a central role in food production, water regulation, carbon storage, and ecosystem habitat.

Soil formation, or pedogenesis, is driven by climate, organisms, relief, parent material, and time. Weathering of rocks produces minerals; organic matter accumulates from litter and roots; biological activity mixes and transforms the material. Over time distinct layers, called horizons, develop: an organic-rich O horizon, an A horizon, sometimes an E horizon from leaching, a B horizon with accumulations, a C horizon of partially weathered material, and the R bedrock below.

Soil properties include texture (proportions of sand, silt, and clay); structure (aggregation); porosity and water-holding capacity; pH; and nutrient levels. Microbial activity and soil fauna regulate nutrient cycling, decompose litter, and form aggregates that improve aeration and drainage.

Soil types are broadly classified by their texture, structure, and horizon development, with common categories such as sandy, loamy, and clay soils, as well as organic soils like peat. Management aims to sustain fertility, prevent erosion, maintain drainage and biodiversity, and reduce pollution.

Human activities such as deforestation, overgrazing, and intensive agriculture can degrade soil, while practices like crop rotation, cover crops, reduced tillage, and organic matter addition help preserve it.