FANR 3060 1st Edition Lecture 12Outline of Last LectureI. Soil Density con’tII. Managing Soil Physical PropertiesOutline of Current LectureI. Soil ChemistryChapter 5I. SoilChemistrya. Soil as a chemical systemi. Micropores filled w water = soil solutionii. Liquid phase contains solutes in equilibrium with solids1. Solute = the things that are dissolvediii. Cations1. Positively charges ions2. Small in sizeiv. Anions1. Negatively charged ions2. Larger in size because of electron cloud around themb. Soil colloidsi. Charged, high surface area solidsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.ii. Adsorb solutes from solution (release back)iii. >2 microns in sizeiv. Two types1. Permanent chargea. Clay minerals2. Variable chargea. Iron oxides and humusb. Vary with pH of soilc. Clay Mineralsi. Type of soil colloidii. Secondary mineralsiii. Permanent negative chargeiv. Composed of silicon/aluminum with oxygend. Kaolinite i. Type of clay mineralii. 1:1 mineral1. 1 sheet of Si tetrahedrons bonded with 1 sheet of Al octahedronsa. Tetrahedron = shape of 4 oxygens packed around one silicon moleculeb. Si has a coordination number of 4c. Octahedron = shape of 6 oxygens around one aluminumd. Al has a coordination number of 6iii. H-bonding occurs between each 1:1 unitiv. Most common clay mineral in GAv. Doesn’t shrink or swell much1. Water can’t get into the interlayera. Interlayer = layer between 1:1 unitsvi. See Figure 5.1 in booke. Montmorillonitei. Also known as smectiteii. 2:1 clay mineral1. 2 Si tetras sandwiching 1 Al octaiii. Interlayer contains no H-bonding1. Water can get in (adhesion)2. Causes shrinking/swellingf. Illitei. First weathering product of micaii. 2:1 clay
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