NRES 201 Lecture 28 Outline of Last Lecture I General Concepts II Significance of soil acidity alkalinity III Active acidity IV Potential acidity V Aluminum as a source of soil acidity Outline of Current Lecture VI Factors contributing to soil acidity VII Soil as a buffered system VIII Determination of soil acidity IX Estimating time requirement Current Lecture Factors contributing to soil acidity Plant roots o H released upon uptake of basic cations o Compensated if anion uptake also occurs Rainfall o Leaching of anions causes leaching of cations o Basic cations mainly Ca2 are lost More abundant than acidic cations Retained less tightly than acidic cations o Acid rain Supplied H2SO4 and HNO3 Insignificant in Illinois Fertilizers o Hydrolysis of acidic salts o Effect on leaching losses Increased loss of anions and cations Reduced losses through anion uptake or precipitation reactions o 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 residues o Organic acids released during decomposition Sulfur oxidation o Strip mine spoils can become extremely acidic Determination of soil acidity Active acidity o Measured as soil pH o Mix soil with water or a neutral salt solution in a selected ratio o Salt solutions Reduced variability Lower the pH Potential acidity o Measurements needed Soil pH CEC Total exchangeable bases Estimating 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 curve
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