AGR 2320 Lecture Notes - Lecture 24: Manganese, Chief Operating Officer, Bromothymol Blue

• School: University of Guelph
• Department: Agriculture
• Course: AGR 2320
• Professor: John Lauzon

Document Summary

Agr 2320 lecture 24 soil ph. From high to low ph: sodic soils (11-9, calcareous soils (9-7, humid region arable soils (7-5, forest soils (6-3) Ph electrodes: soil paste in water, 1:2 soil:cacl2 solution. Natural sources: weathering of soil minerals. + + h: breakdown of soil organic matter. R - cooh r coo- + h: rain. Co2 + h2o h2co3 hco3. Anthropogenic sources: application of ammoniacal fertilizers. + h2o + 2h: acidic precipitation. Aluminum toxicity (below ph 5. 7: al3+ al(oh)+2 al(oh)2 reduces root elongation resulting in stubby roots inhibit nodule formation in legumes. Possibility of ammonia toxicity: ph greater than 8 or near urea fertilizer. Possibility of nitrite toxicity ph and elements. Solubility of many compounds increase with decreasing ph: e. g. oxides and hydroxides of fe and al; carbonates. % base saturation = ( non-acidic cations/total exchangeable cations) x 100. Cec = acidic cations (h+, al+3) + base cations (ca+2, mg+2, k+) If more hydrogens added, more base atoms leave.