The amounts of humus in different soils vary greatly. Plants absorb a small quantity of … Soil water maintains the soil texture, arrangement and compactness of soil particles. These increase the rate of humification. The internal composition of earth is not known exactly. These microorganisms are found in the soil at variable depths. Humus percentage in the soil is affected by climatic and biological factors. 385 0 obj <>/Filter/FlateDecode/ID[<1408E21172CF26418DAE4A814F5B7EF9><84FC1119C6E8AD4FA1BA94F90943B2E3>]/Index[358 40]/Info 357 0 R/Length 130/Prev 921226/Root 359 0 R/Size 398/Type/XRef/W[1 3 1]>>stream Water contents above field capacity displace so much of the soil air that the plant roots usually suffer from inadequate aeration and serve to be detrimental. This led to more advanced microorganisms, which are important because they affect soil structure and fertility. These are filled with moisture and air in varying quantities which account for approximately half of the total volume of soil. They act as decomposers … These bacteria, in turn, help the soil in being more porous, humid and also fertile. (Fig. The soil is made up of the following components: (5) Biological system or soil micro-organisms. The mineral constituents of the soil are derived from the parental rocks or regolith. Hence, it has no definite chemical composition. Welcome to BiologyDiscussion! Soil Water: Soil water plays very important role in the plant growth. In the process of decomposition, complex organic matters are converted into simple organic compounds. Humus is a dynamic product and is constantly changing because of its oxidation, reduction and hydrolysis. Soil micro-organisms improve aeration of soil. Protozoa, mites and insects are example of moving organisms. In the cultivated land, percentage of CO2 is much higher than that of atmospheric CO2, but oxygen content in such soil is poorer than the percentage of oxygen in atmospheric air. The process of humus formation is called humification. It has been calculated that in the ploughed layer of cultivated soil over an area of one hectare there may be from 5 to 6 tons of microbial mass and one gram of ploughed soil contains 1-10 thousand million bacteria. What is the reserve food material in red algae? Content Guidelines 2. Before sharing your knowledge on this site, please read the following pages: 1. Diverse populations of soil bacteria and fungi can suppress root diseases. Biological System of the Soil or Soil Microorganisms: The best answers are voted up and rise to the top. There are anywhere from 100 MILLION to 1 BILLION bacteria in just 1 TEASPOON of soil!!! The soil is differentiated into several layers or horizons which can be distinguished from one another by their colours, textures and other characteristics. Important elements which are found in compound state are Oxygen, Si, Fe, Al, N, P, K, Ca, Mg, C, H, etc. At permanent wilting stage, the percentage of moisture in the soil is termed as wilting coefficient or permanent wilting percentage (Fig. 21.4). The availability of soil water to plants depends primarily on its diffusion pressure deficit, often termed the soil moisture stress. The excreta of soil animal is deposited on the surface of soil in the form of casts which increases the fertility of the soil. Share Your PPT File. Share Your PDF File hޤVmO�0�+��ib~;۱����NP�1 �!����j�4����ii��ZN�.�;�y��f^(a� t�)Á�(�a#z��Y��=�Fh�5�X�]$�Y�q�Xe���@�K��t����6 �qz�drl�ݕ�n_�ɇ�B��do4�χ������'����Hh�o�z�P��Q>���U!�Dž��W��y]�A���齽=�?U-�3�����]-�5�[��S�փQU�ۣ�;�M�^�������Q��9�҄��_O�zp7k�L�$PJvk���a!�����/���%�Rɓr\�&�w� ��mҾR����`tSV��Zմ�?��iݹ�'����3��ü �n��uM������Ϋ�����Bq���nzi�(��2DP����@S�D�Sa��<>㑲��l.D� ��Vx� ��Q3�X�ϱF��9����;M�X�$��� ����h��1'�؃U8���Ddfr�>��LhfdD&�����@[��2��V�"�G�W���9u�5�_��D�܋7�'���N{4�I�@��B�m2i���:6-��>bE�B,�˾N��?�jãyR�u���>�����،���l��a�a tqFy~>g Answer Now and help others. Soil biology is the study of microbial and faunal activity and ecology in soil. According to R.F. Soil microorganisms alter the waste constituents through organic matter decomposition, inorganic transformations, and nutrient assimilation. It has much carbon content and less nitrogen. endstream endobj 359 0 obj <>/Metadata 45 0 R/Outlines 54 0 R/PageLayout/OneColumn/Pages 356 0 R/StructTreeRoot 75 0 R/Type/Catalog>> endobj 360 0 obj <>/ExtGState<>/Font<>/XObject<>>>/Rotate 0/StructParents 0/Type/Page>> endobj 361 0 obj <>stream It moves in the direction where capillary tension is more. Here soil means the loose, friable, unconsolidated top layer of the earth crust. 397 0 obj <>stream It is present in soil in the form of organic colloids. Soil developed from the pre-existing rocks, the regolith of the crust. • Soil microorganisms can be classified as bacteria… They are decomposers, eating dead plant material and organisms' waste. Some bacteria and fungi, so-called biocontrol organisms, can inhibit the growth of harmful microorganisms, technical enzymes and enzymes for food production can be isolated from bacteria, yeasts and fungi, which are also major suppliers of pharmaceuticals such as e.g. Soil bacteria and soil fungi are the start of the soil food web that supports other soil organisms and the functions of a healthy soil. Production of growth stimulating substances: Many soil organisms including soil fungi and bacteria produce growth stimulating substances such as 3-Indol acetic acid, Gibberellins and Gibberellic acid in the soil. (ii) Below the litter may be found a layer of partially decomposed organic matter which is known as duff layer. Our mission is to provide an online platform to help students to share notes in Biology. The earth is more or less, spherical and its surface is highly irregular, marked by deep oceans, high mountain ranges and plains in between. (iii) When the duff is decomposed completely into organic substances, the decomposition products, generally called leaf moulds, are accumulated below duff layer. The word soil is derived from a Latin word ‘solum’ meaning earthy material in which plants grow. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments. The ability of soil microorganisms to decompose organic matter is a function of their population complexity. 1. The amount of water held in the soil, when all pores are filled and when drainage is restricted is maximum water holding capacity. �&��%غtv3��lt��E�d��� p�*�U�W'�� It contains water, gases, complex minerals organic substances and micro-organisms. This excess water is called gravitational water. In the decomposition process, a number of complex mineral compounds are also converted into simpler and soluble compounds. The total of all the forces which the plants must overcome to take up water from soil is called soil moisture stress. The minerals represent about 90% of the total weight of the soil. Organic acids and carbon dioxide that are released by decomposition make insoluble phosphates and other unavailable compounds more easily available to plants. ֌Y�5x+�%g&܌ �u��,�jQ��Y�lo�\��&]nX�=���ۼ �dYE:� ���x��$�jA�u�. It is also important from geological, petro-logical, mineralogical and paleobotamcal points of view.