FANR 3060 1st Edition Lecture 13Outline of Last LectureI. SoilChemistryOutline of Current LectureI. Soil Management (No-Till Agriculture)II. Soil Colloids – Permanent ChargeIII. Soil Colloids – Variable ChargeChapter 5I. Soilmanagement (no-till ag)a. Must till a narrow- strip of land to insert seedi. 3-4 inchesb. Previous year’s crop residue is mulch for this year’s cropsi. Absorbs raindrop impact, increases infiltrationii. Lessens erosioniii. Maintains aggregation, increases humus levelsiv. Reduces CO2 emissions compared to plowing1. “Carbon sequestration” lowers the greenhouse effectc. Herbicides must be used to control weeds, diseases, and insectsd. GMO Corni. GMO = Genetically modified organismThese 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. “Roundup ready corn”1. Roundup is an herbicide that will kill every living plant2. This corn isn’t killed, but all other weeds and competing plants are3. Increases yield of cornII. Soil Colloids – Permanent Chargea. Clay minerals have a permanent negative chargeb. Origin of chargei. Substitution of one cation for a “normal” one at time of mineral formationii. 2:1 minerals have more substitutions than 1:1 minerals1. Varies with clay type and locationiii. Isomorphous substitution1. Same shape, different chargeIII. Soil Colloids – Variable Chargea. Fe oxides and humusb. Charge varies with pHi. Contain functional groups that adsorb/release H+ii. A strong acid dissociates completely1. Loses all H+ in watera. Reaction goes all the way to the right2. HCliii. A weak acid partially dissociates in water1. Acetic acid2. Reaction can go both waysc. The amount of dissociation depends on the equilibrium constanti. Also known as “K”ii. The negative log of K is
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