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Root nodule. A simplified diagram of the relation between the plant and the symbiotic bacteria (cyan) in the root nodules. Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. [1] Under nitrogen -limiting conditions, capable plants form a symbiotic relationship with a host ...
Nod factor. The structure of the major Nod factor produced by Sinorhizobium meliloti. Nod factors (nodulation factors or NF), are signaling molecules produced by soil bacteria known as rhizobia in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship ...
The physical properties of soil, in order of decreasing importance for ecosystem services such as crop production, are texture, structure, bulk density, porosity, consistency, temperature, colour and resistivity. [1] Soil texture is determined by the relative proportion of the three kinds of soil mineral particles, called soil separates: sand ...
Soil structure describes the arrangement of the solid parts of the soil and of the pore spaces located between them (Marshall & Holmes, 1979). [1] Aggregation is the result of the interaction of soil particles through rearrangement, flocculation and cementation. It is enhanced by: [1][2] the precipitation of oxides, hydroxides, carbonates and ...
Soil physics is the study of soil 's physical properties and processes. It is applied to management and prediction under natural and managed ecosystems. Soil physics deals with the dynamics of physical soil components and their phases as solids, liquids, and gases. It draws on the principles of physics, physical chemistry, engineering, and ...
Soil texture. Soil texture is a classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and quantitative methods such as the hydrometer method based on Stokes' law.
Soil aggregate stability is a measure of the ability of soil aggregates— soil particles that bind together—to resist breaking apart when exposed to external forces such as water erosion and wind erosion, shrinking and swelling processes, and tillage. [1][2] Soil aggregate stability is a measure of soil structure [3] and can be affected by ...
Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that are buried in soils. [6] Example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems.