Nitrogen

The amount of nitrogen given to a potato crop varies from 100-200 kg/ha.
In a graph the growth of crops with low,medium and high nitrogen are presented.


Low nitrogen
When nitrogen application is low the canopy development is insufficient for good light interception. As a consequence production is low.
Such a crop also matures too early to reach high production.

Excessive nitrogen
High nitrogen dressing stimulates haulm growth, delays tuber formation and delay maturing of the crop. At high nitrogen, the haulm growth is abundant, tuber growth starts late, bulking rate is high and yield is high if crop matures.The high nitrogen crop is a risky crop since it takes a long time to mature.
Excessive nitrogen and delay in maturity may cause low dry matter content, high reducing sugar content and high protein and nitrate content. Immaturely harvested tubers are easily damaged and difficult to store.
Dry matter and sugar content in tubers

Medium nitrogen
The medium nitrogen crop gives, in the example presented, the highest yield if harvested between the end of July and middle of August.
The medium nitrogen crop is considered to be the safest crop, since it still matures relatively early and yields high. Crops with high nitrogen dressing are more susceptible to secondary growth and to virus diseases.

Split application
Nitrogen is given shortly before or at planting. Split application may be better if there is a risk of leaching (e.g. with light soils-heavy watering), or if the application of large quantities of fertilizer near the seed tuber may cause scorching. In general a second nitrogen application should be given no later than 3 weeks after emergence.

Deficiency symptoms
Nitrogen 1------Nitrogen 2