The
growth of root is not intentional to a nutrient source. For nutrient intake to
occur in plant, the individual nutrient ion must be in position adjacently to
the root. Positioning of the nutrient ion can occur by one or more of three
processes shown below.
Root Interception
The root of the plant can bump into
the ion as it grows through the soil. This mechanism is known as root
interception. About one percent of the nutrients in a corn plant come from the
root due to the interception process.
Diffusion
Nutrients such as phosphorus and
potassium are absorbed strongly by soils and are usually available in small
quantities in the soil solution. These nutrients move to the root by diffusion.
As intake of these nutrients occurs at the root, the concentration in the soil
solution in close proximity to the root while it decreases. This creates a
gradient for the nutrient to diffuse through the soil solution from a zone of
high concentration to the depleted solution adjacent to the root. Diffusion is
responsible for the majority of the Phosphorus, potassium and Zinc moving to
the root for intake.
Mass Flow
The soluble fraction of nutrients present
in soil solution, they are not held on the soil, fractions flow to the root as
water is taken up. This process is known are mass flow. Nutrients such as
nitrate, calcium and sulfur are usually supplied by mass flow.
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