Complete "Soil" guide part 1

1.Soil : a. Soil provides support and nourishment to plants. b. Soil helps plants to grow. It is the base of agriculture. c. The survival of all plants and animals and their nourishment depends upon the soil. 2. Constituents of soil : Stones, pebbles, sand, fine soil particles and organic substances are the various constituents of soil. 3. Formation of soil - weathering of rocks : The process by which rocks are transformed into soil is called weathering. a. The weathering of rocks and formation of soil are affected by various element of nature. b. Changes in the atmosphereic heat and cold, winds, etc. Bring about the weathering of rocks. c. The weathering of rocks and boulders also occurs due to the effects of rivers, rainwater, winds and continuous changes in the weather. Owing to this , rocks and boulders are converted into smaller particles which ultimately form soil. 4. Biological weathering of rocks : a. Rodents like rats and bandicoots that live in burrows help in the conversion of rough earth into soil. b. Roots of the plants growing into the cracks in rocks play an important role in the weathering of rocks. The soil formed is generally clay . 5. Time : It takes about 800 to 1000 years for the formation of a 2.5 cm thick layers of fertile soil. 6. Soil - a natural resource : a. Plants life has developed on the earth owing to the presence of soil. b. Plants provide food to animals and human beings. c. Plants meet our three basic needs-food, shelter and clothing. d. Minerals and metals are also obtained from soil.