BIO 201: Botany
PLANT METABOLISM

SOIL NUTRIENTS

Carbon (C), Hydrogen (H) & Oxygen (O) are not considered nutrients

   Yet, they of great importance to plants since they are in large quantities in environment

MACRONUTRIENTS – mineral nutrients needed in large quantities, essential for plant growth

   element (symbol): % of plant – common form

   Nitrogen (N): 1.5% - NO3- or NH4+

   Potassium (K): 1.0% - K+

   Calcium (Ca): 0.25% - Ca2+

   Phosphorus (P): 0.2% - H2PO4-

   Sulfur (S): 0.2% - SO4=

   Magnesium (Mg): 0.2% - Mg2+

MICRONUTRIENTS - Mineral nutrients needed in small quantities

   include Boron, Manganese, Zinc, Molybdenum, Copper, Chlorine, Iron

   many have unknown importance

Some nutrients can be recycled:
     moved from older parts to young parts. 
    eg.: N, P, Mg, K

Some nutrients needed continuously from soil:
     * mechanism of uptake is active transport into epidermal cells from soil
     * then transport up stem though xylem

Form of uptake:
    1) simple ions: K+, Mg2+, Fe3+
    2) as oxidized ions: PO43-, SO42-, NO3-
              once taken up must be reduced: NO3-  à NH4+

CATION EXCHANGE SYSTEM

Ability of soil to exchange & hold ions
    * large soil particles (-) charged;
    * attract and hold (+) charged

Plants take up lose cations (+)
    * replaced with H+ in soil
    * cation exchange frees up ions from soil particles
    * soil recharged through decomposition

Movement of soil nitrogen
Organic nitrogen   --------------->  NH4+  ------------->  NO3-
                            mineralization                   nitrification

   Ammonia (NH4+) rapidly used by bacteria and plants

   Nitrate (NO3-) easily lost from soil (negatively charged)

Sands & silts - have low cation exchange capacity
    contain very few charged soil particles
    results in leaching

loams, clays, mucks - have high capacity

FERTILIZERS

Organic – from decomposition of organic matter
    * slow release, long lasting, more natural

Inorganic – chemically produced, commonly from petroleum
    * fast release, quick acting, typically artificial source
    * measured as:
Nitrogen (NH4 or NO3) : Phosphate (PO4) : Potash (K2O)
    fertilizer containers with percentage of each: 8-10-5