The Importance of Nitrogen for Citrus

The Importance of Nitrogen for the Best Mandarins, Calamondins, Kumquats, Australian Finger Limes, Oranges and Lemons

The Importance of Nitrogen for the Best Mandarins, Calamondins, Kumquats, Australian Finger Limes, Oranges and Lemons

Mani Skaria, Ph.D.


Nitrogen is a vital element required for life, whether it is plants, or animals, including the human being. Nitrogen is the most abundant element on earth as it occupies about 78% of the atmosphere. The figure at the right is the symbol of Nitrogen as per the periodic table. N = nitrogen, 7 is the atomic number, and 14.007 is the relative atomic mass. At room temperature, it is a gas. The presence of nitrogen was discovered in 1772 by a Scottish physician, chemist and botanist – almost 2½ centuries ago.

For human beings, nitrogen is required to make proteins in our muscles, skin, blood, hair, nails and our genetic material, the DNA. And in nature, human beings obtain nitrogen from animal products such as meat, mild, eggs, fish and plant products such as legumes, and nuts. products, mild, egg, and fish, foods such as meat, fish, legumes and nuts.

A basic difference between plants and animals

Animals can move. Plants are sedentary.

When a physician advises on protein deficiency, the patient takes the information and make corrective measures for themselves and even for their dependents, including the pets. People and animals can move around Whereas, most plant owners are not plant doctors; they have no clue that that plant needs food and water. As a plant doctor, I consider it an unforgivable sin.

Why Citrus plants need nitrogen?

  1. Nitrogen is the key components of the following six functions identified for a citrus plant
  2. When the entire leaf becomes light green to yellow
  3. When leaf drop leaves prematurely.
  • Enzymes
  • Vitamins
  • Chlorophyll
  • Protein
  • Many other plant cell constituents
  • An essential component for fruit growth & development

How much nitrogen is needed?

This generic question comes with a qualifier question – a baby or a mature tree?

A baby tree or a mature adult heavy-fruiting tree?

A baby tree is one to two years-old and a heavy-fruiting tree is over 7-years-old.

A mature tree would benefit from getting about one-kilogram nitrogen per tree per year (= slightly over two pounds). This can be spread over 12-montgh period. However, the best time to apply nitrogen has the following consideration.

What’s the best time to apply nitrogen?

There must be enough nitrogen in the plant before the flowering season. The flowering season in Texas, Florida and California is a Spring-season phenomenon; however, it can start as early as February.

I remember a word of wisdom given to Texas citrus growers by Dr. Richard A. Hensz, developer of the red grapefruits, Rio Red and Star Ruby. His answer to the question, “what’s the best time to apply nitrogen” was, between December 31st and January 1st. What Dr. Hensz meant was that nitrogen must be readily available to the plant a long before the onset of flowering.

Translate this into having enough money in your bank account before you pour the concrete foundation for your new home.

Just like people eating breakfast, lunch, and dinner, the nitrogen application can be spread over 12 months. But remember, just like a good breakfast, enough nitrogen before the flower set in the month of February is important.

How do I know my citrus plant is suffering from nitrogen deficiency?

  • By doing a leaf tissue analysis and when the Nitrogen content is below 2% from the laboratory report
  • When the entire leaf becomes light green to yellow in color
  • When leaves drop premature - normally, a citrus leaf is to last 18 to 24 months.
  • When nitrogen deficiency is severe, plants show stunted growth.

Specific positive roles of adequate Nitrogen

  1. Increase yield
  2. Increase number of fruits per tree

Specific negative roles of too much Nitrogen

  1. Reduce fruit color break from green to orange/red
  2. Increase peel thickness which is considered negative
  • Increase fruit acidity which can be considered negative

Growing trees is fun, but if you want to have delicious, seasonal citrus fruit right away, join the Craft Citrus Club!

Get a curated box of fresh-harvested citrus fruit from South Texas sent to your door every month!

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  • What type of fertilizer and what NPK value would you recommend.

    Jorge Carreon on

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