NRES 201 Lecture 28 Outline of Last Lecture I. General ConceptsII. Significance of soil acidity/alkalinityIII. Active acidityIV. Potential acidityV. Aluminum as a source of soil acidity Outline of Current Lecture VI. Factors contributing to soil acidity VII. Soil as a buffered systemVIII. Determination of soil acidity IX. Estimating time requirementCurrent LectureFactors contributing to soil acidity- Plant rootso H+ released upon uptake of basic cationso Compensated if anion uptake also occurs- Rainfallo Leaching of anions causes leaching of cationso Basic cations (mainly Ca2+) are lost More abundant than acidic cations Retained less tightly than acidic cationso Acid rain Supplied H2SO4 and HNO3 Insignificant in Illinois- Fertilizerso Hydrolysis of acidic saltso Effect on leaching losses Increased loss of anions and cations Reduced losses through anion uptake or precipitation reactionso Nitrification Produces acidity Neutralizing effect of plant uptake Excessive NH4 applications are acidifying These 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.- Liming and N fertilizer usage- Organic residueso Organic acids released during decomposition- Sulfur oxidationo Strip mine spoils can become extremely acidicDetermination of soil acidity- Active acidityo Measured as soil pHo Mix soil with water or a neutral salt solution in a selected ratioo Salt solutions: Reduced variability Lower the pH- Potential acidityo Measurements needed: Soil pH CEC Total exchangeable basesEstimating soil lime requirement: Titration Procedure:- Treat soil sample with a known amount of acid (HCl) or base [Ca(OH)2]- Allow to equilibrate- Measure the pH- Treat other soil samples with different amounts of acid or base- Plot a titration
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