Presentation is loading. Please wait.

Presentation is loading. Please wait.

GES175, Science of Soils Lecture 10 Phosphorus. Phosphorus Soil-Plant Relations * Energy and reproduction * Growth and development a root growth a maturity.

Similar presentations


Presentation on theme: "GES175, Science of Soils Lecture 10 Phosphorus. Phosphorus Soil-Plant Relations * Energy and reproduction * Growth and development a root growth a maturity."— Presentation transcript:

1 GES175, Science of Soils Lecture 10 Phosphorus

2 Phosphorus Soil-Plant Relations * Energy and reproduction * Growth and development a root growth a maturity (seed set, flowering,...) * Maintained by organic matter cycling Slide 10.2

3 Water Quality accelerated eutrophication P (often) promotes algae growth - may promote anoxia and lead to ‘dead’ zones P from point and nonpoint sources Slide 10.3

4 Phosphorus Fixation * Limited Biological Availability P reacts strongly with soil material - limits bioavailability - limits transport through soil - movement occurs via erosion Adsorbs and precipitates Slide 10.4

5 Adsorption Reactions * Strong adsorption on soil minerals - adsorption on Fe- and Al-oxides - adsorption on ‘edge’ sites of silicate clays (dominantly kaolinite) Slide 10.5

6 Volcanic Ash ëë Slide 10.6

7 Inorganic P Compounds (precipitates) Acid soils 8 Fe and Al phosphates FePO 4 2H 2 O, AlPO 4 2H 2 O Alkaline soils 4 Ca and Mg phosphates Slide 10.7

8  Ca(H 2 PO 4 ) 2  monocalcium phosphate  CaHPO 4  dicalcium phosphate  Ca 3 (PO 4 ) 2  tricalcium phosphate  3Ca 3 (PO 4 ) 2 Ca(OH) 2  hydroxyapatite  3Ca 3 (PO 4 ) 2 CaCO 3  carbonate apatite decreasing solubility Inorganic P Compounds Slide 10.8 pH 6 8

9 Nomenclature H 3 PO 4 = phosphoric acid H 2 PO 4 - = monobasic HPO 4 -2 = dibasic PO 4 -3 = tribasic Slide 10.9

10 acid soils alkaline soils soils Phosphate Ion: Protonation Slide 10.10

11 Most Available P between pH Slide 10.11

12 Organic Soil Phosphorus * % of total soil P is organic * Mostly inositol phosphates, C 6 H 6 (OH) % of organic-P - some nucleic acid and phospholipids Slide 10.12

13 Organic-P Slide (available P) Cycling: A slow release mechanism H x PO 4 x-3 mineralization immobilization Solid Phase-PO 4 (unavailable)

14 Symbiotic Relation: Fungi and Plants Mycorrhizae root infections, a key to phosphorus uptake Fungal hyphae mycorrihizae Plant r oot

15 The End

16 Reactions at High pH Values * P converts to less soluble Ca and Mg compounds Ca(H 2 PO 4 ) 2 + CaCO 3 + H 2 O  2 CaHPO 4  2H 2 O + CO 2 very less soluble soluble 6 CaHPO 4  2H 2 O + 3 CaCO 3  3 Ca 3 (PO 4 ) CO H 2 O less soluble 3 Ca 3 (PO 4 ) 2 + CaCO 3  3Ca 3 (PO 4 ) 2  CaCO 3 very insoluble - most serious in calcareous soils of arid regions Slide 10.11


Download ppt "GES175, Science of Soils Lecture 10 Phosphorus. Phosphorus Soil-Plant Relations * Energy and reproduction * Growth and development a root growth a maturity."

Similar presentations


Ads by Google