Tiêu đề Soil physics and Soil conservation (1).pdf ✅

Soil Conservation and Soil Physics (SSC 121, 2+1) Compiled by: Sanket Kattel (NPI) Nepal Polytechnic Institute (NPI) Effects or impacts of land degradation include:  Decline in the chemical, physical and/or biological properties of soil  Reduced availability of potable water  Lessened volumes of surface water  Impacts on livestock and agriculture e.g. loss of animals due to dehydration, reduced yields.  Decline in productivity  Water and food insecurity  Biodiversity loss. Desertification A large dry, barren region, usually having sandy or rocky soil and little or no vegetation. Water lost to evaporation and transpiration in a desert exceeds the amount of precipitation; most deserts average less than 25cm of precipitation each year, concentrated in local brusts. Desertification is a type of land degradation in which a relatively dry land region becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors. Desertification is a significant global ecological and environmental problem.

Soil Conservation and Soil Physics (SSC 121, 2+1) Compiled by: Sanket Kattel (NPI) Nepal Polytechnic Institute (NPI) Erosion refers to detachment and transport of soil and soil material by water, wind, ice or gravity. It is essentially a three steps process involving : detachment, transport and deposition of soil particle. Causes of erosion/Forms of erosion Soil erosion can be broadly classified as (1) geological erosion, and (2) accelerated erosion. A. Geological/Natural/ Normal erosion: This erosion process is also referred to natural or normal erosion as it takes place naturally by the disruptive action of water, wind and gravity, but without the influence of human activities. Geological erosion is that which occurs under natural environment of undisturbed vegetated conditions. It includes processes of weathering and removal of materials by gravity, wind, water and ice. The processes have been active throughout geologic times. It is generally beneficial because it proceeds at a slower than that at which new soil is being formed. As the addition of weathered minerals into the solum is equal or higher than the soil loss at surface, it is regarded as a soil sustaining process. Therefore natural erosion is rather a necessary evil. In Nepal at least 75% of the slides are natural. Mass wasting Mass wasting by natural (geological or normal) process is unavoidable. Large amount of sediment are the result of spot mass wasting rather than the accelerated erosion. Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, sand, regolith, and rock move downslope typically as a solid, continuous or discontinuous mass, largely under the force of gravity, frequently with characteristics of a flow as in debris flows and mudflows. B. Accelerated erosion Accelerated erosion means the quick removal of soil from the land surface due to mismanagement of the land, which includes excessive grazing and deforestation of lands and cultivation of soil, exposing crops without adopting proper soil conservation measures. Accelerated erosion includes wind erosion and water erosion. Accelerated erosion induced by man is a rapid process and it proceed at a rate greater than soil formation, truncates soil profiles and in time destroys the soil. This will results in loss of top soil together with plant nutrients, thus reducing the fertility of the land.