Which of the following is NOT a symptom of excess fertilizer in the root zone?

When considering the symptoms of excess fertilizer in the root zone, a rich green color is typically indicative of healthy growth and sufficient nutrient availability, rather than a problem caused by over-fertilization. In fact, while it can be a favorable sign in moderate conditions, when fertilizer is excessively applied, plants can sometimes show an exaggerated green color due to rapid but unsustainable growth. This vigorous growth can lead to various stress factors, such as water deficiency or susceptibility to pests.

In contrast, wilting occurs as a response to root stress caused by high salinity and poor water uptake due to fertilizer burn. Marginal burning is a direct indication of tissue damage from nutrient overdose, which can cause the leaf margins to brown and die. Dieback refers to the decline of plant health, often leading to the death of stems and branches, which can also be triggered by excess fertilizer that disrupts root function and water absorption. Therefore, while the other symptoms reflect negative effects of high fertilizer levels, a rich green color does not fit this context.