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The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described below (with the exception of Pt):
The activity of soil is the ratio of the plasticity index to the clay size fraction. If activity is less than 0.75, the soil is inactive. If activity exceeds 1.4, then the soil is termed active. If activity lies within the above values, then the soil will be moderately active. [10]
The Universal Soil Loss Equation (USLE) is a widely used mathematical model that describes soil erosion processes. [1]Erosion models play critical roles in soil and water resource conservation and nonpoint source pollution assessments, including: sediment load assessment and inventory, conservation planning and design for sediment control, and for the advancement of scientific understanding.
Raunkiær's life-form scheme has subsequently been revised and modified by various authors, [6] [7] [8] but the main structure has survived. Raunkiær's life-form system may be useful in researching the transformations of biotas and the genesis of some groups of phytophagous animals.
Acta Agriculturae Scandinavica. Section B. Soil and Plant Science is a peer-reviewed scientific journal published by Taylor & Francis on behalf of the Nordic Association of Agricultural Scientists. It covers environmental sciences, botany, earth sciences, physical geography, ecology, and the soil sciences of relevance to agriculture.
Soil aeration maintains oxygen levels in the plants' root zone, needed for microbial and root respiration, and important to plant growth. Additionally, oxygen levels regulate soil temperatures and play a role in some chemical processes that support the oxidation of elements like Mn 2+ and Fe 2+ that can be toxic.
This theory, which considers the soil to be in a state of plastic equilibrium, makes the assumptions that the soil is homogeneous, isotropic and has internal friction. The pressure exerted by soil against the wall is referred to as active pressure. The resistance offered by the soil to an object pushing against it is referred to as "passive ...
The type and amount of vegetation depend on climate, topography, soil characteristics and biological factors, mediated or not by human activities. [104] [105] Soil factors such as density, depth, chemistry, pH, temperature and moisture greatly affect the type of plants that can grow in a given location. Dead plants and fallen leaves and stems ...