Nutritional Problems

Like many crops, tobacco needs various minerals for growth and good leaf quality. Its fertilisation is quite complex because it is particularly affected by:

- the richness and balance of soil nutrients (soil tests are essential);
- type of tobacco grown and the variety chosen;
- the use or not of supplementary irrigation and the resulting leaching;
- planting density;
- any other factor interfering with plant growth.
 
Given this situation, it is not uncommon to encounter  field plants with deficient or excessive fertilisation. These disorders are called non-parasitic diseases that we have grouped under the heading of Nutritional problems . Their symptoms are quite frequently yellowing of different degrees on different plant areas. A few of these nutriotional deficiences also induce deformation of a leaf shape, in particular:
 
- Lack of potassium (K): chlorosis (often referred to as 'firing') is more or less marked at the leaf tips and sometimes at margins, accompanied by necrotic spots. The lower leaves are curved towards the underside of lamina surface (figures 3 and 4). 
- Calcium (Ca) deficiency:  the leaf apices tend to curve downward and become necrotic (figure 2);
- Boron deficiency (B) in tobacco means insufficient amount of this trace element which induces a slowdown of cell wall development, in particular at the growing points of plants. Consequently the plant growth is diminished. In addition, the leaves of apical buds turn light yellow and stop growing. Some older leaves are abnormally ?cut? (figure 4).

When speaking about deficiencies, we tend to associate real deficiencies with induced deficiencies. Real deficiencies (i.e. a deficiency of nutrients in the soil) are increasingly rare, their diagnosis is very difficult de visu because, the symptoms they normally cause are discoloration and more or less intense yellowing of the leaves, which are very difficult to assess by a non-specialist.

In most cases we are dealing with induced deficiencies (nutrient elements are present but unavailable), which complicates diagnosis. In addition to determining the nature of the deficiency, we also have to find out the causes. They can be various, such as poorly managed irrigation (too much or not enough water), too low or too high temperature or soil pH, poor root systems, etc.

When you are faced with these kind of symptoms, you should take your time before drawing a conclusion of deficiency. Ask help from a technician and consult a specialist and carry out the necessary physical and chemical analyses of soil and vegetation. 

For further information, please see the fact sheet of Nutritional Problems in the section of Abnormal leaf colour.