PO 24. Recognize how the following affect plant tissue analysis results.

When utilizing plant tissue analysis, it may be helpful to take samples from the problem area and a nearby "normal" area for comparison.  Use all available information to interpret the plant analysis for diagnosing a nutrient deficiency.  Look carefully at the symptoms on the plants, note any patterns in the field, and consider the timing of the problem's appearance.  Keep in mind that not all nutrient deficiencies in plants are the result of nutrient deficiencies in the soil.  Soil testing and plant analysis can confirm each other, but they also can indicate when the cause of the problem is something other than a nutrient deficiency in the soil.  If the soil test level is adequate but the plants are deficient, some other factor is limiting the plant's ability to take up available nutrients.  Some factors to consider include possible interactions with other cultural practices such as tillage or pesticide use; pest injury such as rootworm feeding; differences in varieties or hybrids; or soil physical conditions such as compaction.

• Leaf symptoms are only guides to the source of the trouble: don't use them alone!
• Usually, under field conditions, more than one deficiency symptom is present; therefore, symptoms are complicated
• Diseases may enhance nutrient deficiencies and vice-versa

Stress of any type can produce or enhance plant symptoms.  For instance, the purple coloring of corn in spring is brought on by cold stress and/or too-deep cultivation.  Similarly, pruning plant roots can result in K deficiency, and Zn deficiency is often the result of poor root growth.