Citrus is the most extensively produced tree fruit crop in the world. It is growing in a wide diversity of climatic and soil conditions. its importance for the world is demonstrated by its wide-scale cultivation under tropical and sub-tropical conditions. Also, it has a tremendous socio-economical and cultural impact on the whole society. The multifold nutritional and medicinal values make this type of fruit indispensable in several parts of the world. Citrus is primarily valued for the fruit, which is either eaten alone as fresh fruit, processed into juice.

The Role Of Elements

Potassium plays an important role in improving the productivity and quality of citrus crop and the crop's need for potassium increases significantly during the stage of growth and development of fruits, so it must be added in sufficient quantities to ensure optimal growth of fruits. The most important roles also:

  • Increasing productivity, improving fruit characteristics quality and increasing their exported windows.
  • Increases sugar and coloring content in fruits.
  • Increases flowering, fruit set and decrease fruit drop.
  • Increases plant resistance to various pathogens (fungal - insect).
  • Increased plant resistance to environmental stress factors i.e. (High temperature - frost - drought - salinity).
  • Increases the ability of roots to absorb the nutrients and plays a major role in carbohydrates and nitrogenous substances balance by reducing the excessive amount of nitrogen.

Phosphorus plays an important role in improving the productivity and quality of citrus crop. The most important roles of phosphorus for citrus crop: -

  • Improves and boosts flowering, pollination and fertilization.
  • Improves growth and roots distribution, especially in the beginning of spring growth.
  • Has a vital role in improving vegetative growth.
  • Maintain long-term productivity.
  • Improves the quality of fruit juice.
  • Give fruits with good export specifications.

Calcium considered one of the most important effective nutrients on citrus crop. Some of the   physiological roles of calcium in citrus are:

  • Important and necessary on root growth and distributions as well as vegetative growth.
  • Increases fruit set and decreases fruit drop.
  • Reduces physiological disorders of fruits such as creasing and splitting.
  • Increasing the storage ability of citrus fruits on markets.
  • Increasing plant resistance to insect and fungal pathogens due to increased hardness of plant cell walls.

Deficiency Symptoms


Potassium deficiency Symptoms appear on leaves in form of yellowing in general, in addition to burning of external leaves edges; moreover, potassium deficiency leads to reduction of yield and decreases fruit quality.

  • Poor fruit set and decreases both yield and fruits quality.
  • General weakness appears on vegetative growth when potassium deficiency occurs.
  • Potassium deficiency leads to death of young leaves while old one become wrinkle and leathery. Moreover, leaves suffer from decrease of chlorophyll content which appear as of irregular yellow spots that fall at the end of flowering period.
  • Trees become less resistant to unfavorable environmental stress.
  • General weakness appears on trees with poor vegetative growth.
  • Poor sugar and coloring content in fruits.


Trees suffer from phosphorus deficiency are small leaves with a dark green color and the leaves turn bronze and fall early. Phosphorus deficiency also leads to:

  • Decreases in vegetative and root growth.
  • Increases percentage of flowering and fruit set falling.
  • Fruits become highly acidic.
  • A thick peel of fruits with a rough texture.
  • Phosphorus deficiency may limits absorption of other elements.


Calcium deficiency symptoms on citrus crop appear wrap the leaves in the form of a hook and the leaves are light green in addition , as calcium shortage it is leads to:-

  • Poor root growth and distribution.
  • Decreases fruit set and increases both flowers and fruits drop percentage.
  • Some physiological disorders of fruits were appearing such as creasing and splitting.
  • Decreases storage ability of fruits in the markets.
  • Deformation of young eaves with poor growth.
  • Death of the terminal buds of branch.