LaMotte Soil Chemistry Test Equipment - Manual (Page 11)

THE MAJOR PLANT NUTRIENTS
The major essential nutrient elements supplied through the soil are
nitrogen, phosphorus, and potassium. The nutrients absorbed from the soil
by plants are supplied by several means. These include minerals released
from the decomposition of native rocks, decomposition of organic matter,
deposition with the soil from flood waters, application of limestone and
commercial fertilizer materials, and the use of animal or plant manures.
Much of the nitrogen, phosphorus, and potassium in the soil is chemically
“bound” and cannot be readily absorbed by growing plants. To provide an
accurate profile of soil fertility, LaMotte soil tests measure strictly the
available forms of these nutrients.
• AVAILABLE NITROGEN
Nitrogen is a part of every living cell. As a component of amino acids, the
building blocks of protein, nitrogen is a vital link in the world’s food
supply. Nitrogen is directly involved in photosynthesis. It stimulates
above-ground growth and produces the rich green color characteristic of
healthy plants. Nitrates, the available forms of soil nitrogen, are produced
through the decomposition of organic matter, the application of nitrogen
fertilizers, and the fixation of atmospheric nitrogen by microorganisms
growing on legume roots. Soil nitrogen is depleted through harvesting of
crops, leaching by rain water, and return of nitrogen to the atmosphere by
volatilization.
• AVAILABLE PHOSPHORUS
Young plants absorb large amounts of phosphorus, which speeds seedling
development and promotes early root formation. Rapid, early growth
means hardier, stronger plants. In mature plants, phosphorus is vital to the
development of healthy seeds and fruits which contain large amounts of
this essential nutrient. Only a small percentage of soil phosphorus is in an
available form and these phosphates move more slowly through the soil
than other nutrients.
• AVAILABLE POTASSIUM (POTASH)
Potassium acts as a catalyst, a chemical agent which facilitates a number
of chemical processes in the plant. Potassium promotes various aspects of
plant metabolism -photosynthesis, efficient use of water, and the formation
of strong roots and stems. Well-described as a “tonic” for plants,
potassium strengthens natural mechanisms for the resistance of disease
and extremes of weather.
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