ROLE OF NITROGEN IN APPLE
Nitrogen is a primary nutrient that plays a vital role in apple production and high yields. Nitrogen is one of the important nutrient primarily responsible for vegetative growth of apple tree. Healthy apple tree contains 2 to 6 percent nitrogen in plant tissues. Nitrogen is a major component of chlorophyll which is essential for photosynthesis, producing sugars from water and carbon dioxide. Nitrogen is a major element of amino acids which are building blocks of proteins. These proteins are used in the form of enzymes and nucleic acids.
NITROGEN UPTAKE BY APPLE TREE
In soil nitrogen exists in three basic forms
- Organic Nitrogen
- Ammonium ions (inorganic nitrogen)
- Nitrate ions (inorganic nitrogen)
In soil 95 to 97 percent nitrogen is available in organic form. Organic nitrogen is nitrogen tied up with organic matter which is unavailable to apple tree. Only 2 to 4 percent nitrogen is in the inorganic form of nitrate and ammonium form which is available to the plant. The organic form of nitrogen is broken to inorganic nitrogen by microorganisms. This process of breaking of organic nitrogen to inorganic nitrogen is known as mineralization. There is an opposite process of immobilization in which microorganisms feed on inorganic nitrogen making the nitrogen unavailable to the plant.
Most of the nitrogen absorbed by the roots of apple tree is in nitrate form and to a lesser extent is in the form of ammonium.
Ammonium nitrogen carries a positive charge and is derived from ammonia. It is most commonly found in soil as ammonium which is created naturally by nitrogen cycle or introduced through fertilizers. A long-term effect of all ammonium-based nitrogen fertilizers is to lower soil pH. The ammoniacal nitrogen is converted to nitrate form by bacteria.
Nitrate form of nitrogen is directly absorbed by the roots of the apple tree. It carries positive charge and is not adsorbed onto soil; so it is free to be leached out from soil. Nitrate nitrogen also can be lost to the atmosphere through denitrification when soils become water saturated. Nitrate moves freely toward plant roots as they absorb water.
KEY ROLE OF NITROGEN
- It is element of all amino acids which are building blocks of proteins.
- It is a responsible for vegetative growth of apple tree.
- It helps in better photosynthesis rate.
- It helps in cell division.
- It serves as source for dark green color in leaves.
- It helps in exhibiting vigorous tree growth.
- Excess nitrogen delays fruit color.
- Excess nitrogen can also result in small fruit size.
- The chlorophyll content is reduced hence yellowing of leaves is primary symptom of nitrogen deficiency.
- There is reduction in proteins which results in stunted growth.
- It results in poor flowering and fruit set.
- Nitrogen deficient tree result in smaller fruit size.
- Urea (46-00-00) (N-P-K)
- Calcium Nitrate 15.5% Nitrogen
- Potassium Nitrate (N-P-K) (13-00-45)
- CAN Calcium Ammonium Nitrate 26% Nitrogen
- Ammonium Nitrate 35% Nitrogen
- Calcium Cyanamide 20.6% Nitrogen
- Ammonium Sulfate Nitrate 26% Nitrogen
NITROGEN LOSSES FROM THE SOIL
- Volatilization loss (loss of gaseous ammonia to the atmosphere)
- Denitrification (conversion of nitrate to other forms of nitrogen)