Study guide question for Midterm#3 NRES201- CEC calculation- Lime calculationCh11. Soil Organic Matter (OM) OM provides much of the soil’s CEC and waterholding capacity-large quantities of plant nutrients and act as slow-release nutrient storehouse-supplies energy and body-building constituents for most of the microorganisms Carbon CycleCarbon- compromise half of the mass of OM. Carbon in OM contains 3x greater than that of all worlds vegetation--plays a big role in global carbon balance (greenhouse effect)- Understand how the rate of decomposition associated with different OM components.Rapid decomposition to very slow decomposition1. Sugars, starches, simple proteins2. Crude proteins3. Hemicellulose4. Cellulose5. Fats and waxes (leaf coating)6. Lignins and phenolic compounds (slow due to rigid/strong chemical structure)Background: Plant residues are the primary material undergoing decomposition in soils-60-90% water weight. Remaining dry matter= carbon, oxygen, and hydrogen C6H10O5. -ash contains nutrient elements from soil. Contain elements other than CHO (N, S, Ca)-- Know factors controlling the rate of decomposition and mineralization.Factors: 1) environmental conditions of soil. 2) quality of the added residues as a food source for soil organisms.1) sufficient soil moisture, good aeration (60% of the soil pore space filled with water), andwarm temperatures (25-25 C). 2) C:N ratio, physical condition of the residues, and their content of lignin and polyphenols.Decomposition: breakdown of large organic molecules into smaller, simpler componentsMineralization: process that releases elements from organic compounds to produce inorganic forms. Usually the last step in decomposition process- Can you explain aerobic and anaerobic decomposition processes of soil carbon?R-(C, 4H) + 2O2 è CO2 (g) + 2H2O + energy (478kJ/mole)Aerobic: See Figure 11.41. Enzymatic oxidation (enzyme catalyzes oxidation) of carbon compounds to produce CO2, water, energy, and decomposer biomass2. Release and/or immobilization of the essential nutrient elements (N, P, S) by a series of specific reactions 3. Formation of compounds in the original tissue or by microbial synthesis. Resistant to further decayIn aerobic decomposition, living organisms, which use oxygen, feed upon the organic matter. They use the nitrogen, phosphorus, some of the carbon, and other required nutrients. Much of the carbon serves as a source of energy for the organisms and isburned up and respired as carbon dioxide (C02). Since carbon serves both as a source of energy and as an element in the cell protoplasm, much more carbon than nitrogen is needed. Generally about two-thirds of carbon is respired as C02, while the other third is combined with nitrogen in the living cells. However, if the excess of carbon over nitrogen(C:N ratio) in organic materials being decomposed is too great, biological activity diminishes. Several cycles of organisms are then required to burn most of the carbon. When some of the organisms die, their stored nitrogen and carbon becomes available toother organisms. As other organisms use the nitrogen from the dead cells to form new cell material, once more excess carbon is converted to C02. Thus, the amount of carbon is reduced and the limited amount of nitrogen is recycled. Finally, when the ratio of available carbon to available nitrogen is in sufficient balance, nitrogen is released as ammoniaAnaerobic:-Occurs when oxygen is depleted in saturated soils. Very slow process so these soils accumulate large amounts of OM in partially decomposed conditions. -Release relatively little energy, so the end products (alcohols and methane) contain much energy. Foul odor, inhibit plant growth, contributor to greenhouse effect -methanogenic bacteria carry out the following reaction4C2H5COOH + 2H2O è 4CH3COOH + CO2(g)+ 3CH4(g)Propionate bacteria acetate methane- Know the difference between heterotroph and autotroph.Heterotroph: Organisms cannot synthesize their own food and rely on other organisms (e.g., carbon sources from plant residues)Autotroph: Organisms that can produce their own food from the substances available in environment (e.g., light, CO2).(=Self feeders, Primary producers)- Explain how C/N ratio influences the Organic Carbon decomposition.- How does OM influence on soil properties?- Know how to define/classify the soil OM? (e.g., humic acid, humin, active, slow and passive)- How do we gain soil carbon?- Is conservation or conventional tillage practices bad to sequester soil C? Please justify your answer.- How do we lose soil carbon from soils? (I want you to answer chemical reactions and practices).- Know the organic carbon distribution in North America. Can you explain why?- How do natural vegetation, soil texture and drainage affect the formation/accumulationof OM in soils?- Please name greenhouse gases that are produced from soil. Please explain how they contribute to the greenhouse effect.- What practices can we do to decrease the production of greenhouse gases from soils?- Explain different types of compositing methods. How do they work?- What are benefits of compositing?- How do you efficiently create “compost” at home?Ch10 Organisms and Ecology of Soils - Explain the role of species diversity and functional diversity in our ecosystem.- Can you explain why functional redundancy, stability, resilience, and genetic resources are important in our ecosystem?- How are “different types of biodiversity and ecosystem dynamics” affected by OM content/pesticide applications?- Name primary, secondary and higher level consumers, and know their relationships.- Can you define autotrophs and heterotrophs? If so, which organisms fall into each category? - Describe the step-wise activities of meso- and micro-fauna to enhance the decomposition of plant residues?- Which soil organisms make the major alternations to the physical properties in soils?- How do earthworms contribute to the soils? Are they any different types of earthworms? Discuss as many soil properties that are affected by earthworms and their by-products.- Understand the role of ants and termites in soils? Do they both make soils more productive?- Justify your answer.- What are nematodes? What is the role of nematodes in soils? Do they contribute to soil nutrient cycles? If so how?- What is rhizosphere? Know