BIOA02H3 Lecture Notes - Lecture 11: Nitrogen Cycle, Biogenic Substance, Bioavailability

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5 May 2018

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BIOA02 Module 1 Lecture 11: Plant Nutrition and

Soils

Essential Nutrients

• Absence prevents plant from completing its life cycle

• Macronutrient: required in relatively large amounts

• Micronutrient: required in relatively small amounts

• N, P, K are the most limiting nutrients

Nitrogen N

• Essential building block for life, basic metabolism, photosynthesis

• Atmospheric overabundance 78% N2 bioavailability through bacteria

• Young soils N limited until bacteria build up N levels

• Young soils: sand dunes, newly deglaciated areas, volcanic islands

• Building blocks of life: amino acids → proteins

Biogenic Nitrogen Cycle

• Nitrate  nitrite Ammonia  Amino acids  Decomposition  Soil bacteria  N-

Fixation  Atmosphere: N2 78% → lightning → nitrate

Phosphorous P

• Promotes early plant growth and root formation → role in cell division

• Essential for flowering and fruiting

• Low bioavailability in soils: highly reactive P precipitates and mostly is bio-unavailable

Potassium K

• Important in the process of sugar and starch production

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