The Influence of Nitrogen on Wheat

Nitrogen (N) is often the most deficient of all the plant

nutrients. Wheat is very sensitive to insufficient nitrogen and very responsive to nitrogen fertilization. The most important role of N in the plant is its presences in the structure of protein, the most important building substances from which the living material or protoplasm of every cell is made. In addition, nitrogen is also found in chlorophyll, the green coloring matter of leaves. Chlorophyll enables the plant to transfer energy from sunlight by photosynthesis. Therefore, the nitrogen supply to the plant will influence the amount of protein, protoplasm and chlorophyll formed. In turn, this influences cell size and leaf area, and photosynthetic activity.

Deficiency Symptoms
The most easily observed symptom of nitrogen deficiency is the yellowing (chlorosis) of leaves due to a drop in chlorophyll content and pale green (chlorotic) plants that are poorly tillered  . This symptom is usually noticed first in the more mature leaves, and last in the upper actively growing leaves, because the N is translocated from older to new leaves to sustain growth. Thus, the older leaves will wither and result in poor plant growth and yield reduction. Generally growth is slowed, stunted and firing of the leaf tips and margins is evident.

Excessive Symptoms
Excessive N can cause lodging, increased disease incidence and severity, and lower yield. Additionally, excessive N may result in increased levels of N in ground and surface waters, with negative environmental (and economic) consequences.  Nitrogen must be applied in a timely manner to maximize yield potential. Delaying N application after to an N-deficient crop will result in decreased yield potential most years.  Proper N rate and timing are important for high tiller numbers and yield .

The Wheat Growth Rule 
Before winter, it adopts large amount of nitrogen fertilizer,and the less amount of phosphatic fertilizer and potassic fertilizer. In order to satisfy the nitrogen fertilizer demand, people used to spread 1.5-2.5 kg nitrogen fertilizer to increase wheat growing. During wheat seedling period, it stills need more nitrogen fertilizer,but with the increasing amount of phosphatic fertilizer and potassic fertilizer. The fertilizer applied in Winter mainly plays its role in spring.

Wheat Nutrition
By the time the grain formation period starts nutrients accumulation is practically over and the formation of grain is progressing due to nutrients redistribution. During the stage of tillering and initiation of ear primordium spring grain crops need nitrogen more then ever – they take up to 40% of nitrogen consumed during the whole vegetation period.  Phosphor helps on the root system development, large ear formation, earlier maturing. Shortage of phosphorus causes bad assimilation of nitrogen and potassium.  Initial growth period is critical with regard to nitrogen and potassium. Shortage of these nutrients reduces crop yield by 20-30%.

Fertilizer N Sources.
Fertilizer N sources for wheat include ammonium nitrate (33-34% N), urea (45-46% N), and urea-ammonium nitrate solutions (28-32% N) chemical fertilizer and so on . All are equally good sources of wheat N nutrition,  Wheat requires a small, but important, amount of N in the fall. in all tillage systems and regardless of previous crop residue. This requirement can almost always be met by soil N remaining after the preceding corn. Slow release N is now available for use on wheat. resulting in greener wheat.