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Importance of soils

  The ‘soil’ means the natural body covering the earth surface as a thin layer resulting from the transformation or decomposition of rocks and minerals, with organic matter mixed together to become a homogeneous substance.

            The soil is important to human and all living things on earth because it is the source of four essential ‘living’ factors, namely, food, clothes, shelter and medicine, all of which either directly or indirectly coming from the soil. For plants, the soil is very important to their growth and yield because for plants to be able to grow and bear flowers or fruits they rely on the soil as the base for their roots can adhere so that their trunks can stand strongly and firmly, not to fall down easily. The soil is the source of nutrients necessary for the plants to use in various productive processes to create flowers, leaves and fruits. Besides, the soil is also the water storage or the moisture that plants will absorb to feed their trunks and branches and the source of air for the plants to transpire too. In a soil with good air ventilation, the plant’s roots can grow strongly, can absorb more water and nutrients, enabling the plants to grow strongly and yield high production.

            The soil is composed of minerals (the solid part), organic matter and air in different proportions. The formation of a soil results from the co-action of various factors such as, climate, plants and other living things towards the parent material of a soil in a specific area through an interval of time. Therefore, a soil in a certain place may be similar to or different from another soil in another place, depending on the influence of these factors which may be more or less in the extent in each area, with effects to their specific characteristics. When these factors change, the soil’s characteristics or properties will also change.

             The most important factors influencing the soil formation consist of five factors including climate, parent material, topography, organism and the time that controls the process of addition, change, movement and loss of matters and energy that occur in the soil. The formation of all soils is controlled by these five factors all the time and it cannot lack any factor, just the influence of all five factors in each time interval may be different. In certain period, one factor may play an outstanding role in controlling the soil characteristics and properties more than the other factors; for example, a soil in its initial stage of development, the parent material will play an important role, the soil characteristics and properties will come from its parent material, which is easily noticeable. When the time has passed by, the role of the parent material will decrease so that sometime it is not possible to categorize the kind of the parent material.

 1. Climate
The important ‘climatic factors’ that significantly affect the formation of a soil are the temperature and precipitation such as rain, dew, snow, etc. These various factors control physical, chemical and biological reactions that affect the decomposition rates of various materials, e.g. rocks, minerals and organism remains. The climate also influences the process of addition, changes, movement and loss of various materials occurring in the soil too. Besides, the climate also affects to the kind of living things, which is the factor controlling the formation of soil too. In general, the soils found in the tropical zone would be those that have passed through much development in the soil formation process and would always lack fertility because the high temperature and moisture content can accelerate the decomposition process of materials, and various processes continue rapidly, resulting in the state of continuous loss of nutrients out of the soil.

 2. Parent material 
The ‘parent material’ means the material that has passed through the changes and development and mixed with organic matter to become a soil. It may have occurred from the direct decomposition of rocks, minerals and living things’ remains in that area or having moved from other places by water, wind or glazier or having deposited at the foot of the mountain by gravity. The type of parent material influences various characteristics and properties of the resulted soil, such as soil texture, soil color, the kind and content of plant nutrients in the soil. 

 3. Topography 
The ‘topography’ herein means the relief, slope and the aspect of slope that influence the temperature and moisture content in a soil, underground water level, the growth of vegetation, decomposition of rock, rates of run off and permeability, soil erosion, accumulation of organic matter in the soil. In general, a soil found at a very steep slope would be a shallow soil, having small soil content, thin topsoil or possibly without the topsoil at all; it is sensitive to erosion, being different from a soil at the foot of the hill that would have thicker topsoil and deep soil strata.

 4. Living things 
The ‘living things’ herein mean plants and animals, large and small, visible and invisible, including human. They affect many changes of the soil properties. The remains of plants and animals are the sources of organic matter in the soil whereof various living things including micro organisms in the soil enhance the decomposition in physical, chemical and biological processes that enables the soil properties to suit the growth of plants and to be the natural source of nutrients in the soil.

 5. Time 
The ‘time’ role concerns the soil formation that includes both the real time that a soil starts development from its parent material which is the soil’s real age and the ‘relative time’ that means the level of soil development. A soil that has passed through the more violent soil forming process is regarded as an older soil. We can use some soil characteristics and properties for determining the ages of soils, such as the depth,the thickness and the color of soil, etc.

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