Study guide question for Midterm 3 NRES201 CEC calculation Lime calculation Ch11 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 Cycle Carbon 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 decomposition 1 Sugars starches simple proteins 2 Crude proteins 3 Hemicellulose 4 Cellulose 5 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 and warm 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 components Mineralization 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 CO2 g 2H2O energy 478kJ mole Aerobic See Figure 11 4 1 Enzymatic oxidation enzyme catalyzes oxidation of carbon compounds to produce CO2 water energy and decomposer biomass 2 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 decay In 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 is burned up and respired as carbon dioxide C0 2 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 C0 2 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 to other organisms As other organisms use the nitrogen from the dead cells to form new cell material once more excess carbon is converted to C0 2 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 ammonia Anaerobic 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 reaction 4C2H5COOH 2H2O 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 accumulation of 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 important terminologies functions associated with rhizosphere What is the role of algae in soils Where do we observe them in soils and why What is the role of fungi in soils Can you describe any positive and negative effects caused by soil fungi What are mycorrhizae Explain how they contribute to soil environment What is the role of bacteria actionomycete in