The ALGL agronomy staff is regularly quizzed about the value of tissue testing. Often the focus is to verify a visual nutrient deficiency, then determine what foliar fertilizer to spray. While this is a valid application of the management tool, there are greater benefits to be had by using the information to avoid the issue in the future.
Think of the tissue test as a report card for your overall crop and soil fertility management plan. With a tissue test collected just before and during key physiological growth periods of the crop can help find week points in the overall soil/crop fertility plan. If a deficiency is found a quick rescue maybe the applications of a soil or foliar fertilizer, but how do you avoid the same situation occurring in the future? The greatest value in tissue testing is not only identifying a fertility issue and correcting it now and adjusting in your soil/crop fertility management plan to avoid the recurrence of the situation, while using routine soil and tissue testing to verify the correction of the issue.
A simple example. You notice areas of your soybean field showing interveinal yellowing of younger leaves. The tissue test confirms that the plant is deficient in manganese. The quick response is a foliar application of manganese to correct the issue. A soil test collected at the same time as the tissue test shows low levels of manganese in the soil, so the cause of the plant deficiency was due to the soils inability to supply the nutrient. The foliar application addresses the symptoms, but not the cause. Without proactively addressing the soil fertility issue along and/or planned foliar applications, the issue most likely will reoccur in the future. The knowledge from the tissue and soil test can help drive changes in the crop/soil fertility plan to avoid the issue in future years in conjunction using tissue and soil tests in future crop season to confirm the change in the plan continues to correct the issue.