Review Questions for Hour Exam 2 Fall 2014 Soil Organic Matter What is soil organic matter and what are its functions How does residue decomposition vary with C N ratio How do soil orders vary in organic matter content What effect has synthetic N fertilization had on soil organic matter levels in the Morrow Plots Soil Water How do polarity and H bonding affect the properties of water What causes capillarity What affects the height and rate of capillary rise in soils How does water flow in relation to potential What are the four potentials that determine the energetics of soil water Which one is most important How is soil water classified with respect to saturation field capacity the wilting coefficient the hygroscopic coefficient and oven dryness How is gravimetric water content calculated What two factors cause infiltration and how do infiltration rates compare for fine versus coarse textured soils What distinguishes saturated from unsaturated flow Why and how is water flow restricted in stratified soils How does water move by vapor equalization How do texture and organic matter content affect soil water availability The Hydrologic Cycle How has water management changed over time and what is the major use today How is water balance estimated for a watershed How do foliar interception and runoff compare for a deciduous forest versus a corn field How does cover cropping help to increase soil water storage What is water use efficiency and how does it compare for arid versus humid regions How can evaporation and transpiration be controlled What are furrow basin flood sprinkler and drip irrigation Which is most efficient and why How do surface and subsurface drainage differ Which is more important in Illinois How does soil type determine the agricultural need for tile drainage How does subsoil permeability affect tile spacing and depth Soil Management Erosion How does geological erosion differ from human accelerated erosion Which one predominates today How does water erosion occur What is the role of raindrop impact versus runoff What are the three types of water erosion What factors affect water erosion and how are they represented in the Universal Soil Loss Equation USLE What factors affect soil erodibility How does terracing reduce water erosion How do conservation tillage systems reduce water erosion and which one is most effective How does wind erosion occur and what is the main transporting process What factors affect wind erosion and how can it be controlled Soil Aeration Temperature How are soils aerated How and why does soil air differ in composition from ambient air What changes occur when a soil is waterlogged What is redox potential Eh and how does it relate to soil aeration How does soil temperature affect aeration status How do plants adapt to poor soil aeration What are the two fundamental requirements that define a wetland soil What are three properties that can be used as hydric soil indicators How does frost heaving occur How effective is solar radiation for heating the soil How is soil heating affected by albedo and aspect How do growing plants cool the soil How does evaporation cool a wet soil What can be done to manage soil temperature Colloidal Properties What are the two sources of negative charge on clay minerals Classify the following as 1 1 2 1 or 2 1 1 clay minerals Kaolinite Montmorillonite Vermiculite Illite Chlorite Is this a 1 1 or 2 1 clay mineral and where is the isomor2phous substitution Al2 xMgx Si4O10 OH 2 nH2O Al4Si4O10 OH 8 K2 x Ca Mg x Si4 yAly Al2O10 OH 2 nH2O Mgn H2O 6 Si4 xAlx Al2 yFey O10 OH 2 nHO Is cation exchange capacity CEC directly related to unit layer charge For what kind of soils would hydrous oxides be an important source of CEC How is CEC measured Which cation is held most tightly to exchange sites Which is held least tightly Ca2 Mg2 K Na H Which type of soil colloid is highest in CEC Clay minerals Hydrous oxides Organic matter Which type of soil colloid is highest in anion exchange capacity AEC Clay minerals Hydrous oxides Organic matter What is the source of positive charge for AEC How does soil acidity affect CEC and AEC How does soil weathering affect CEC and AEC How are nonpolar organic compounds retained in soils