ISB 202 9-11-08 - ISB 202 9-11-08 Soil microbes below...

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ISB 202 9-11-08 Soil microbes below ground increase rapidly when organic matter is added to the soil They use N from the soil to form their bodies They immobilize the soil N and plants can’t get it Plants may show N deficiencies even though there is a lot of organic matter in the soil o So, how do plants get this immobilized N? Microbes soon die – this releases the N back into the soil environment This release of N is called mineralization Plant roots can take up this released nitrogen to form more organic matter This is one reason why having organic matter in soils is important o Is this the only way Nitrogen gets into the soil? No! Nitrogen for plant use comes from several sources Commercial fertilizers Soil organic matter Lightning Fixation by bacteria o Certain bacteria (Rhizobium spp) make a deal with plants o The bacteria live in nodules they form on the plants roots o And “fix” N from soil air into a form plants can use o Plants send sugars (Ps) to their rots and the Rhizobia use these Called symbiosis – a relationship in which two organisms live
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This note was uploaded on 04/21/2011 for the course ISB 202 taught by Professor Johnson during the Fall '08 term at University of Michigan.

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ISB 202 9-11-08 - ISB 202 9-11-08 Soil microbes below...

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