The Relationship Between Soil Properties and Soil Erodibility - Essay Example

The Relationship Between Soil Properties and Soil Erodibility Introduction Soil erodibility is influenced by individual site factors such as topography vegetation, and rainfall; however, beyond these influences, the single most important factor in soil erodibility is the soil's properties, both physical and chemical (Rhoton, Emmerich, Goodrich, McChesney & Miller, 1998, p. 415). Physical and chemical properties of soil Physical properties of soil The different physical properties of soil 1. Soil Texture 2. Soil Structure 3. Soil Consistence 4. Soil Color 5. Topography 6. Land use Soil texture Soil constituents are sand, silt, clay and soil texture is about the size and shape of these constituents. The composition of sand, silt and clay in a soil is natural phenomenon and the composition cannot be modified on any large scale by man . Among sandy, loamy and clayey soil loam soil is a ideal textural class .It contains the constituents like sand silt and clay in uniform proportions. It has the largest water holding capacity which helps to absorb water during the rain and helps in reducing soil erosion (Genna Dunjo Denti,2004, p.125). Soil Structure Soil Structure refers to the shape, size and degree of development of soil by aggregation. Soil aggregates are group of soil particles that are bonded together strongly to each other than to the adjacent particles with the help of organic matter. The space between the aggregates provides pore space for retention and exchange of air and water. Desirable aggregates are stable against rainfall. When less organic matter is used to bind these aggregates, due to rainfall these aggregates break down and leads to soil crust formation, this crust in turn increases the infiltration and air permeability, this in turn disturbs the surface soil and sub-soil structure. Thus inclusion of organic matter aids in the formation of stable aggregates and strengthen them. They also increase the porosity of the soil for air and water movement. Thus aggregating helps in reducing soil erosion. As the strength aggregates depends on the organic matter, since the organic matter acts as a binder to the aggregates. Hence weakening of this bond due to frequent tillage ultimately breaks down the aggregate structure of surface soil (Rachman, Anderson, Gantzer and Thompson, 2004, p. 31). Soil consistence Soil consistence describes the cohesion among soil particles and the adhesion of the soil to other substance that help in combating the wind and rainwater. Splash erosion is the removal of sand by impact of raindrops on the soil surface, this is also known as soil splash detachment (Jean Poesen, Gerard Govers(2001), p.1,2). If the soil is loose and friable, it has the maximum water holding capacity. This water holding capacity of soil stops soil erosion due soil splash detachment. If the soil is too loose it is very much prone to both the wind and water erosion. Wind erosion includes moving of the soil particles due to wind velocity and when these moved soil particles collide with the other particles and break them .If this continues then the soil is eroded by the wind. Wind also makes some soil particles to remain suspend in air and stay there till the wind continues leading to erosion. Water erosion mainly removes the soil particles by force of water and loss of various soil particles into ground water through infiltration. This leads to rapid dry out of soil due to lack of moisture holding capacity and leachate of minerals and other desirable elements. If the soil is dense, more overland flow may increase the erosion rate (Dr.Cooper, 2005, chapter-2). Soil Color Soil color is one of the physical indicators of soil condition. Soil color is most easily determined characteristic and helps in determining the other characteristics of soil like water-able depth and chemical constituents. Surface soil Surface-soil is the top most layer of the soil and is in interference with the atmosphere. This soil comprises of the organic matter such as manure and dead plants and leaves. Sub-soil is the layer of the soil just below the upper most surface soil layer. This layer consists of sand, silt and clay. Sub-soil is the hold for the roots of the plants and has water-holding capacity. Different soil has different color Organic matter is darker. Gray tones tend to indicate poorly drained soils. Pale shades tend to indicate the leached soils. Any unusual color change in the soil indicates that the soil is prone to erosion. The most undesirable is the sight of lighter patches in the field that results due to the loss of top- soil and disturbance of sub surface. This leads to surface run off and ultimately to soil erosion. (Rhoton, Emmerich, Goodrich, McChesney & Miller, 1998, p. 417). Topography Topography refers to the lay of land with geographic terms that include elevation, slope, slope length, slope angle etc. The different geometrical variables that can influence soil erosion are 1.Slope angle 2.Slope length Steeper slopes that have greater slope angles leads to great amount of soil loss and soil erosion due to surface runoff. Slope positions Summit-The highest point of any landform for example hill. Shoulder: The hill-slope position that forms a gently inclined surface at the base of a slope. Foot-slope: The hill-slope position that forms the inner, gently inclined surface at the base of a slope. Back-slope: The hill slope position that forms the steepest and generally linear, middle portion of the slope (glossary of social science terms). High iron and clay, low carbon and water contents in summits and shoulder area are more prone to erosion than low iron and clay, high organic carbon and water contents in foot slope and toe-slope areas. Land use Land use has more effect on erosion than the other factors. Vegetation cover has the biggest effect on soil erosion. This effect the soil in all of its dynamics, including water distribution over and within the soil and disturb the soil structure and lead to soil erosion. Human activities like deforestation, urban developments and fire aid in depleting the soil and are important factors that lead to all kinds of soil erosion. Forestland distribution is generally used for logging and reseeding. Rangelands are the lands where the cattle grazing, this avoids over grazing and reduces soil erosion. Techniques to reduce soil erosion are 1. Grass 2. Forest 3. Land Leveling 4. Conservation tillage 5. Manure application to the surface soil Grass and forest give the complete ground cover throughout the year and hold the soil through their roots. This is the easiest method to control soil erosion. Land leveling or terracing: During the heavy rainfall on leveled lands, the velocity of water run-off is reduced and this consequently reduces soil erosion. Manure application: Applying manure to the surface of the soil. This manure acts as a binder to the soil particles on the surface and holds them together. This reduces the soil erosion to a great extent. Chemical properties of soil 1.Cation exchange capacity 2. Soil pH Major elements Soil consists of negatively charged anions of oxygen in the form of clay and organic matter in the soil. This negative charge is dependent on both clay and organic matter but the majority of negative charge comes from the organic material. Positively charged cat-ions of other common elements are iron sodium and potassium. This organic matter serves as a water reservoir as these organic matters have affinity towards the water. This affinity property of organic matter towards the water helps soil to adsorb the water. This water absorbing capacity helps in reducing soil erosion. Colloidal clays present in the soil have a negative charge and this negative charge has high affinity to adsorb water and influences the water adsorptive capacity (Genna Dunjo Denti,2004, p.168). Cat-ion Exchange Capacity Cat-ion exchange capacity of a soil is simply a measure of the quantity of sites on soil surfaces that can retain positively charged ions by electrostatic forces. Cat-ion exchange capacity depends on the quantity of clay and organic matter in the soil. Mostly depends on the organic matter. The organic material helps in nutrient retention capacity by the soil, acts as a binding agent. This binder holds the negative charges in the soil and is exchanged by the cat-ions. The cat-ions are easily attracted by the anions and the balance is maintained between the cat-ions and anions. This influences the soil ability to act up-on cat-ions in the soil pores. This greatly influences the soil structure and soil porosity that maintains the infiltration rate. When these soil structures are disturbed by erosion or excessive tillage then the infiltration rates vary and this causes imbalance in cat-ion exchange capacity. (Genna Dunjo Denti, 2004,p.168) Soil pH Soil pH has its influence on many other properties of soil. Soil pH indicate the alkalinity and acidity of the soil. Soil pH decreases as the hydrogen ion activity increases. Plant growth is strongly impacted by soil's pH as knowing soil's pH one can determine whether the applied pesticides and insecticides are taken by the plants or not. Soil Environmental Properties 1.Soil Solution 2.Soil Temperature Soil solution The aqueous liquids having ions is found within a soil. This water in the pore network has a great influence on the physical and chemical properties. The amount of clay and organic matter has affinity towards the water and adsorb them and this helps to reduce erosion. This maintains the physical and chemical properties of soil. The increase in the content of soluble salts in the soil leads to soil erosion. This is because soluble salts in the soil increase the osmotic pressure and simultaneously becomes harmful for plants. If these soluble salts in the soil reach the soil surface, they evaporate and leave salt crystals on the soil surface and with the increase of salt crystals a impermeable salt crust will form over the soil diminishing infiltration. Thus soluble salts make the soil structure vulnerable to erosion. (Genna Dunjo Denti,2004,p.131) Soil temperature More the organic material in the soil the more the climatic factors acting on the soil. The more the organic matter in the soil the soil becomes strong and resistant towards erosion. Conclusion While some factors cannot be changed in terms of the potential for erodibility in a specific location, many others, including tillage, can significantly improve the soil's ability to retain sufficient moisture and resist the harmful effects of wind and rain. Long term effect of tillage is usually negative -It decreases organic materials -Breaks down structure -Most importantly, it removes protection cover of plants and residue References Arriaga, F. J., & Lowery, B. (2003). "Soil Physical Properties and Crop Productivity of an Eroded Soil Amended with Cattle Manure", Soil Science. 168(12):888-899. Gemma Dunjo Denti(2004)."Developing a desertification indicator system for a small Mediterranean catchment: a case study from the Srra Derodes,Alt emporida Catalunya,Ne Spain" Social Science Unit Bryan, R.B. (2000). "Soil Erodibility and Processes of Water Erosion on Hillslope", Geomorphology, Vol. 32, no. 3-4, pp. 385-415. Crosson, Pierre, Brubaker, Sterling. (1982). 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