Plant Nutrients
     Nutrients required for plant growth are divided in macronutrients (primary & 
     secondary) and micronutrients based on the quantities of the nutrients needed. In 
     addition to these, the plant also needs Hydrogen, Oxygen and Carbon, which the 
     plant acquires from the air and from water. 
     Primary            Secondary           Micronutrients:       Other elements with a 
     Macronutrients: Macronutrients:                              role in plant nutrition:
     Nitrogen (N)       Calcium (Ca)        Iron (Fe)             Sodium (Na)
     Phosphorus (P)     Sulfur (S)          Manganese (Mn)        Cobalt (Co)
     Potassium (K)      Magnesium (Mg)      Zinc (Zn)             Vanadium (V)
                                            Copper (Cu)           Silica (Si)
                                            Boron (B)             Aluminum (Al)
                                            Molybdenum (Mo)       Barium (Ba)
                                            Chlorine (Cl)         Nickel (Ni)
                                                                  Titanium (Ti)
                                                                   Photo credit: Scot 
                                                                   Nelson
       Plant Nutrients
             Essential nutrients               Chemical form assimilated                   Average plant content
                     Carbon                                  CO2                                      45%
                   Hydrogen                                  HO                                        6%
                                                               2
                    Oxygen                                 HO & O                                     45%
                                                            2      2
                    Nitrogen                             NH+ & NO -                                   1.5%
                                                             4      3
                                                             -        2-
                  Phosphorus                           HPO  & HPO                                     0.2%
                                                         2   4        4
                                                                +
                   Potassium                                  K                                       1.0%
                    Calcium                                  Ca2+                                     0.5%
                                                                2+
                  Magnesium                                  Mg                                       0.2%
                     Sulfur                                  SO2-                                     0.1%
                                                                4
                      Iron                                Fe2+ & Fe3+                              100 ppm*
                                                                2+
                   Manganese                                 Mn                                     50 ppm
                     Boron                                  HBO                                     20 ppm
                                                              3   3
                                                           2+
                      Zinc                              Zn  & Zn(OH)                                20 ppm
                                                                                             Photo credit: Scot 
                                                                                             Nelson
                                                             2+     +
                     Copper                               Cu  & Cu                                   6 ppm
                    Chlorine                                  Cl-                                   100 ppm
                  Molybdenum                                MoO2-                                   0.1 ppm
                                                                 4
         * ppm = parts per million (100 ppm = 0.01 %)
     pH
     pH is a measure of how alkaline or 
     acidic the soil is. This is important, 
     because the pH affects the 
     availability of the nutrients in the 
     soil. 
     A nutrient may be present in the 
     soil, but it may not be available to 
     the plants because of chemical 
     reactions caused by the pH 
     conditions. 
     A pH of between 6.0 and 6.5 is the 
     optimal range where most 
     nutrients are most available for 
     plant use. 
     If not, the soil needs to be 
     amended with lime (for acidic                                 Photo credit: Scot 
     soils). Gypsum can be used for                                Nelson
     sodic soils with high alkalinity.
    Soil Tests
    Soil tests are essential for efficient plant nutrition. Not only do they show the levels of 
    nutrients in the soil, they also show other characteristics such as pH, percent organic 
    matter and cation exchange capacity (C.E.C.; i.e. how good the soil is at holding the 
    nutrients), which helps manage the soil for best results
                                                   Photo credit: Scot 
                                                   Nelson
     Soil Types
     Cation Exchange Capacity 
     Soil types affect plant nutrition and fertilization. Clay soils and soils with a high 
     organic content hold a lot of nutrients (a high C.E.C. or cation exchange capacity). This 
     gives these soils a good buffering capability and they help ensure an efficient 
     fertilization. Sandy soils, on the other hand, have a low C.E.C. with low nutrient 
     holding capacity and little ability to prevent leaching of nutrients.
     Soil Structure
     An ideal soil for plant growth is one that has 50% solids and 50% pore space (filled 
     with 50% water and 50% air).  [Did you know that the roots of a plant use about 10 
     times more oxygen than the leaves? This is because it takes a lot of energy for the 
     roots to extract nutrients from the soil. The oxygen in the air is needed for respiration, 
     which gives the roots the energy.] 
     For the efficient movement of air and water, a healthy soil should have a good 
     structure, which means that it should be organized into macro- and micro-aggregates. 
     Aggregates are groups of soil particles that ‘stick’ together due to organic material, 
     calcium and various natural carbohydrates and acids found in the soil. There are 
     different factors that affect the formation or breakdown of aggregates such as 
                                                                   Photo credit: Scot 
     cultivation techniques, levels of sodium and levels of organic matter.
                                                                   Nelson