Search results
Results from the WOW.Com Content Network
Soil loss tolerance. Soil loss tolerance for a specific soil, also known as the T value, which can be calculated with [1] formula, is the maximum average annual soil loss expressed as tons per acre per year that will permit current production levels to be maintained economically and indefinitely. T values range from 1 to 5 tons per acre per ...
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.
The United States loses almost 3 tons of topsoil per acre per year. [16] 1 inch (2.5 cm) of topsoil can take between 500 [17] and 1,000 years [18] to form naturally, making the rate of topsoil erosion a serious ecological concern. Based on 2014 trends, the world has about 60 years of topsoil left.
Runoff curve number. The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. [1] The curve number method was developed by the USDA Natural Resources Conservation Service, which was formerly called the Soil Conservation ...
Soil retrogression and degradation are two regressive evolution processes associated with the loss of equilibrium of a stable soil. Retrogression is primarily due to soil erosion and corresponds to a phenomenon where succession reverts the land to its natural physical state. Degradation is an evolution, different from natural evolution, related ...
If the soil particles in a sample are predominantly in a relatively narrow range of sizes, the sample is uniformly graded. If a soil sample has distinct gaps in the gradation curve, e.g., a mixture of gravel and fine sand, with no coarse sand, the sample may be gap graded. Uniformly graded and gap graded soils are both considered to be poorly ...
T value. The United States Department of Agriculture defines the T Value as the maximum average soil loss (in tons per year) that will still allow economical maintenance of the current level of production into the future. [1]
Soil erodibility is a lumped parameter that represents an integrated annual value of the soil profile reaction to the process of soil detachment and transport by raindrops and surface flow. [1] The most commonly used model for predicting soil loss from water erosion is the Universal Soil Loss Equation (USLE) (also known as the K-factor ...