Chapter 1 (1-25)

Chapter 1 (1-25) - AGRO 301 Chapter 1 The Soils Around Us I...

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AGRO 301 1/16/08 Chapter 1 The Soils Around Us I) Soils are crucial to life on earth A From ozone depletion and global warming to rain forest destruction and water pollution B Soils will continue to supply us with nearly all of our food C Our dependency on soils is likely to increase, not decrease, in the future. II) Functions of soils in our ecosystem A Supports the growth of higher plants 1) By providing a medium for plant roots and supplying nutrient elements that are essential to the entire plant (a) Plants obtain from the soil (a) Physical support (i) Anchors the root system so the plant doesn’t fall over (b) Air (i) Plants depend on the process of respiration to obtain energy (c) Water (i) The roots absorb water and the soil holds it where it can be used by the roots (ii) The water-holding capacity of soils is essential for plant survival (d) Temperature moderation (i) Soil has insulating properties that protect the deeper portion of the root system from the extremes of hot and cold that often occur at the soil surface (e) Protection from toxins (i) The soil can disperse the concentrations of toxins by ventilating gases, decomposing or adsorbing organic toxins or by suppressing toxin-producing organisms (f) Nutrient elements (i) There are 18 Essential Elements , without which plants cannot grow and complete their life cycles 1. Essential Elements that are used in relatively large amounts are called Macronutrients 2. essential elements that are used in relatively small amounts are called Micronutrients 2) ***plants can also be grown with out soil in a process called Hydroponics *** (a) It has a high energy, money and management levels B Controls the fate of the water system 1) Water loss, utilization, contamination, and purification are all affected by the soil 2) Nearly every drop of water in our rivers. Lakes. Estuaries and aquifers has either traveled through the soil or flowed over its surface C A Recycling system
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1) Waste and dead bodies of plants and animals are assimilated and their basic elements are made available for reuse by the next generation 2) Soils have the capacity to assimilate great quantities of organic waste, thus turning it into beneficial Humus , converting the mineral nutrients in the wastes to forms that can be utilized by plants and animals, and returning the carbon to the atmosphere as carbon dioxide, where it again will become a part of living organisms through plant photosynthesis 3) Some soils can accumulate large amounts of carbon as soil organic matter, thus having a major impact on such global changes as the much discussed greenhouse effect D Provide Habitats for a myriad of living organisms E Engineering medium 1) Important building material in the form of earth fill and bricks 2) Provides the foundation for just about every road, airport and house we build F Soil as environmental interface 1) The importance of soil as a natural body derives in large part from its role as an interface between the worlds of rock (the
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Chapter 1 (1-25) - AGRO 301 Chapter 1 The Soils Around Us I...

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