Plant Health and
There are seventeen
nutrients that, when applied to soil, play a major role in
determining plant health and crop yield.
In order for
plants to absorb these nutrients, the nutrients must be dissolved.
When nutrients are dissolved, they are in a form called "ions" and
are electrically charged.
most soil is
made up of clay and organic matter. Both fractions carry a negative
charge and, since, in soil chemistry, "opposites attract" and "likes
repel", they attract cation (positive) elements and contribute to a
Nutrients that have a positive electrical charge, in their plant
available form, include potassium (K+), ammonium (NH4+),
magnesium ( Mg++), calcium (Ca++), zinc (Zn+),
manganese (Mn++), iron (Fe++), copper (Cu+)
and hydrogen (H+). While hydrogen is not classified as a
nutrient, it directly affects soil pH and is therefore important.
Nutrients that have a negative electrical charge in their plant
available form are called anions and include nitrate (NO3-),
phosphate (H2PO4- and HPO4--),
sulfate (SO4-), borate (BO3-),
and molybdate (MoO4--).
Phosphates are unique in that they are highly reactive and are not
mobile in the soil. Most phosphates will combine with other elements
or compounds in the soil, other than clay and organic matter. The
resulting compounds are not soluble, and will precipitate out of
soil solution. In this state, they are unavailable to plants, and
form the phosphorus "reserve" in the soil.