The Role of Nutrients in Plant Growth - the Major Three

Beginning farmers need to learn the role of plant nutrients in order to be successful at growing crops.  Here is a short description of the three major nutrients plants need from University of Missouri Extension agronomist Travis Harper.

Everyone knows they need to apply fertilizer for optimal growth of plants. But what exactly do those nutrients do for the plant?

Nitrogen

“The primary use of nitrogen in plants is for the formation of proteins,” Harper said. “Nitrogen is also an integral part of chlorophyll. Therefore, a plant with sufficient nitrogen will exhibit vigorous growth and a dark green color while a plant that is nitrogen-deficient will be stunted and yellow.”

Plants absorb nitrogen in the forms of nitrate and ammonium. “Nitrate and ammonium, if not used by the plant, are readily lost from the soil, resulting in the need for yearly application of a nitrogen fertilizer to meet crop needs,” he said.

Nitrogen is the most frequently deficient nutrient in crop production and most non-legume systems require nitrogen inputs.

Phosphorus

The most essential function of phosphorus in plants is energy storage and transfer.

“A plant produces energy when it goes through photosynthesis. Much of this energy is stored by phosphorus in the plant for later use,” he said. “Without phosphorus, this energy would be lost.”

Adequate phosphorus is important early in the life of a plant, when roots and reproductive parts of plants are developing. Ample phosphorus increases root growth, reduces grain-ripening time and increases straw strength in cereal grains.

Large amounts of phosphorus exist naturally in the soil, but it is often not in plant-available form, creating the need for occasional application of phosphorus fertilizers.

Potassium

Potassium is absorbed by plants in larger amounts than any other nutrient except nitrogen. The total potassium content of a soil is many times greater than what a crop needs, but only a small fraction of this soil potassium is available to the plant, resulting in the need for potassium fertilizer application.

Potassium plays a number of roles in the plant, including enzyme activation, water uptake, energy production, sugar transport, nitrogen uptake and protein synthesis. One of the most important of these is water uptake. Potassium gives plants the “pull” that draws water into their roots. Potassium-deficient plants will often exhibit signs of drought stress, even in years when rainfall is adequate.

“As can be seen, nutrients perform a variety of function in the plant and deficiency of any nutrient, major or minor, can affect plant health and overall crop yields,” Harper said. “As always, the best way to determine potential nutrient deficiencies is through soil and plant tissue testing.”

For more information on soil and plant tissue testing services, contact your local MU Extension office or contact the Soil and Plant Diagnostic Services.