22 Why is so much nitrogen lost to atmosphere from fertilizer applied to crops

22 why is so much nitrogen lost to atmosphere from

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22. Why is so much nitrogen lost to atmosphere from fertilizer applied to crops on well drained soils? What does that have to do with anaerobic respiration? 23. How are lithotrophs and anaerobic respirers dependent upon one another? 24. What are three gases that can result from respiration (aerobic or anaerobic). 25. What three greenhouse gases are produced by microbes? Rank them in order of lowest to highest global warming potential. 26. What are some of the impacts on the actual cycling of nutrients (biogeochemical cycling) resulting from microbes changing the oxidation states of elements? Nitrogen cycle 27. What is the difference between nitrification and denitrification? 28. What is difference between N mineralization and immobilization? 29. What is nitrogen fixation and why is it important? What are the major factors controlling the rate of N fixation. Who performs N fixation? Why are symbiotic relationships beneficial for supporting N fixation? Mycorrhizal fungi 30. What is a mycorrhizal association? Contrast the two major kinds we considered and how are they different? How do each of the two partners in a mycorrhizal association benefit from the relationship? 31. Why are these symbiotic relationships less pronounced in agricultural soils than non ag soils?
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Carbon cycle 32. Distinguish between the two major “stages” of carbon flow in soil after organic residues are added. How are microorganisms involved? What roles do soil fauna (invertebrates) play? 33. How does the carbon/nitrogen ratio of a plant residue affect nitrogen availability (to plants) in a soil? 34. Name four major chemical components (polymers) of plant residues. How can microorganisms decompose these if they are so large? 35. Our understanding of soil organic matter (SOM) has change drastically in past 10 years. What is a big surprise about what substances are NO LONGER important in SOM? What is surprise about what are major feedstocks for SOM? Factors controlling processes 36. What major environmental factors control the activity of microorganisms in soil? What is the relationship between i) temperature and ii) water potential and the microbial growth rate.
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  • Fall '08
  • Staff
  • Bacteria, Mycorrhiza, Soil biology

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