Knowra Topsoil Topsoil Topsoil is the uppermost soil layer, enriched by decomposed organic matter and biological activity. It is where most plant roots grow and many soil organisms live.
Soil horizon : A distinct layer in a soil profile formed by processes such as organic accumulation, leaching, and weathering. Topsoil is commonly identified as the A horizon, though boundaries vary among soils.
Soil formation : The development of soil through interactions among climate, organisms, parent material, relief, and time. Topsoil develops as these factors accumulate organic matter and transform surface material.
Soil conservation : Practices that prevent soil degradation and maintain soil functions. Conservation measures protect topsoil from erosion and loss of organic matter.
Dust Bowl : A severe period of dust storms and agricultural collapse on the Great Plains of North America during the 1930s. The Dust Bowl showed how farming and drought could expose and remove fertile surface soil.
Humus : Stable, decomposed organic matter in soil that influences nutrient availability, aggregation, and water retention. Humus gives topsoil much of its dark color and helps it hold nutrients.
Decomposition : The breakdown of dead organic material into simpler substances by organisms and chemical processes. Decomposition returns nutrients and organic compounds to the topsoil.
Cover crop : A crop grown primarily to protect and improve soil rather than for harvest. Cover crops shield topsoil and can add roots and residues that improve it.
Soil carbon : Carbon stored in soil as organic compounds, plant residues, and living organisms. Topsoil often contains substantial soil carbon, which can be lost through disturbance and erosion.
Soil structure : The arrangement of soil particles into aggregates and the pores between them. Topsoil structure controls how roots, air, and water move through its biologically active layer.
Nutrient cycling : The movement and transformation of nutrients among organisms, soil, water, and the atmosphere. Topsoil hosts rapid exchanges that make nutrients available to plant roots.
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