The necessity for study and experience has been stressed in learning
to detect symptoms due to plant deficiencies. It is especially important
to learn to tell the difference between these symptoms and other visual
symptoms that may be present.
The use of herbicides has been a tremendous boost to efficient crop
production. Occasionally, herbicides may be misused and plant injury may
result. This may be mistaken for a nutrient deficiency symptom. The history
of field treatment should be reviewed.
If the symptom is one of a deficiency that is well known to the examiner, then there may be no problem. But often when a plant shows distress signals, the average person has a hard time deciding, "Is it a deficiency or is it a disease? If it is a disease, is deficiency partly responsible for the disease? Could it be nematodes?"
Maybe it's none of these but a matter of too hot, too much water, or too little water.
Frequently these questions are hard for the inexperienced to answer. That's why we do not rely on visual symptoms alone but use every tool.
First. look for insects by examining the roots, leaves, and stems. At the same time use a small hand lens and look for evidence of disease. Of course, to be sure, plants should be taken to a plant pathologist or and entomologist.
A plant analysis, a tissue test, and a soil test are very helpful in
arriving at the answer.
While symptoms differ for different crops, there are some general clues for nutrient deficiencies and some specific symptoms for the individual element deficiencies that can serve as a guide for all crops. A nutrient deficiency should be suspected when these conditions occur: