Soil Fertility - Lecture

Soil Nutrients

  • Plant nutrition: nutrients plants need from soil and atmosphere

  • Fertilization: elements added to soil as an amendment

  • 18 essential plant nutrients

    • photosynthesis: carbon, oxygen, hydrogen

    • soil: everything else

    • macro

      • carbon: 45%

      • oxygen: 45%

      • hydrogen: 6%

      • nitrogen: 1.5%

      • phosphorus: 0.2%

      • potassium: 1%

    • secondary

      • calcium

      • magnesium

      • sulfur

    • micro

      • iron, chlorine, manganese, boron, zinc, copper, nickel

How Soil Gets Nutrients

  • Natural: weathering of rock, decomposition of organic matter, precipitation, bacteria

  • Amendments: fertilizers or compost

    • types of fertilizers

      • synthetic: inorganic and made through individual processes

      • natural: sourced from organic and inorganic materials

        • manure, compost, meal (bone, blood, fish), and lime

How Plants Get Nutrients

  • Key to plant growth: cation exchange

    • negatively charged soils hold cations (+) - calcium, potassium, magnesium

  • Cation exchange capacity: soils ability to hold cations

    • useful measure of soil fertility

    • greatest in fine textured and organic soils

    • decreases with lower pH

  • Soil nutrient absorption: in order for plants to absorb elements they must be dissolved in soil water

    • factors that improve nutrients: type of soil, soil pH, types of nutrients in soil, amount of soil water, climate