ENVS 2060 Lecture Notes - Lecture 18: Cation-Exchange Capacity, Soil Ph, Bromothymol Blue
31 Mar 2016
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Sodic soils (sodium carbonate) = higher bc of carbonates. Ph electrodes: soil paste in water, 1:2 soil:cacl2 solution. Leeching carbonate react with hydrogen (lowers ph) Acid rain or natural rain (ph = 5. 6) reduces ph, adding co2. Weathering of soil minerals: al3+ + h2o aloh2+ + h+ Breakdown of soil organic matter: cooh r coo- + h+ Anthropogenic sources: application of ammoniacal fertilizers (eurea ammonium, acidic precipitation. Sulfur precipitation it is going down. Molybdenum deiciency: microneutrient deiciencies, decreases in availability as ph decreases. Manganese toxicity (ph less than 5. 0: lots of metal micronutrients at low ph. In so, young soils have suicient micronutrients so these aren"t really a problem, not low ph soils. At arrow where elemental aluminum begins to exist, below that you have more. Possibility of ammonia toxicity (ph greater than 8 or near urea fertilizer: ph increases, less hydrogen in soil water, ammonium releases hydrogen and becomes ammonia (as a gas it can exit the soil)
