9788188818167 - the soil and the microbe [hardcover] selman a. waksman (1 Ergebnisse)
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Hardbound. Zustand: As New. New. Contents Foreword. 1. The soil and the plant. 2. The microbe and its activities. 3. The soil population and its distribution. 4. Role of microbes in the decomposition of organic substances in the soil. 5. Transformation of nitrogen by soil microbes. 6. Transformation of nitrogen by soil microbes…(continued). 7. Transformation of mineral substances in soil through the direct or indirect action of microorganisms. 8. Interrelationships between higher plants and soil microorganisms. 9. Modification of the soil population. 10. Importance of microbes in soil fertility. Index. The soil is not a mass of dead debris resulting simply from the physical and chemical weathering of rocks and of plant and animal remains through atmosphere agencies but it is teeming with life. Every small particle of soil contains numerous types of living organisms belonging both to the plant and animal kingdoms yet so small that they cannot be recognized with the naked eye. These organism are therefore called microbes. These microbes comprise numerous types of bacteria fungi algae protozoa nematodes and other invertebrates which vary considerably in their structure size mode of living and relationship to soil processes. In the cycles of transformation of elements in nature the microbes play an important if not a leading role. Were it not for them the soil would soon become covered with a considerable mass of undecomposed plant and animal residues life would soon cease since the very limited supply of carbon and available nitrogen the most essential elements in the growth of living organisms would become exhausted. It should be recalled that carbon dioxide the source of carbon for the growth of plants which in their turn supply the food for animal is present in the atmosphere only in a concentration of 0.03 per cent. This is equivalent to 5.84 tons of carbon over each acre of land. A good yield of sugar cane will consume about 20 tons of carbon in a single growing season of course most of the surface of the earth supports less vegetation than this and diffusion tends to create a uniform distribution of gases. It has actually been calculated that the plant world consumes 64.8 millions of tons of carbon annually which amounts to 1/35 of the total carbon content of the atmosphere. The atmosphere supply of carbon dioxide is however constantly replenished from the decomposition products of the organic substances in the soil only as a result of this does plant growth not cease entirely through a deficiency of an available supply of carbon. In the absence of microbes the available nitrogen would also become very rapidly exhausted as can be appreciated from the fact that this nitrogen is never present in the soil in forms available to plant growth as ammonia or nitrate in amounts of more than a few pounds per acre. It is made available to plants only through the constant activity of the microbes. The microorganisms through their various activities thus enable organic life to continue uninterruptedly on our planet. They keep in constant circulation the elements which are most essential for plant and animal life. They break down the complex organic molecules built up by plants and animals into the simple mineralized constituents making the elements again available for the growth of cultivated and uncultivated plants which in their turn supply further food for animals. Just as man and other animals as well as higher plants find their habitat on the surface of the soil or immediately below it so do the microbes live largely within the upper few inches of the earth's crust where they carry out their important activities supplying a continuous stream of nutrients in an available form for the growth of higher plants. This surface pellicle of the earth is thus found to be the seat of numerous processes of incalculable importance in the life of man animals and plants enabling them to carry out their normal existence on our planet. Just as man and animals are determined in the.
