What are two significant limitations of using trunk implants and microinjections?

The answer identifies two important limitations of trunk implants and microinjections. First, these methods are generally advised for trees that are larger, specifically those over 4 inches in diameter. This restriction is significant because smaller trees may not have the necessary vascular structure to effectively distribute the injected materials, limiting the efficacy of the treatment.

Secondly, trunk implants and microinjections are not suitable for addressing macronutrient deficiencies. These deficiencies often require broader soil amendments or different application methods to ensure that essential nutrients can reach the tree's roots effectively. Trunk injections typically target specific issues or micronutrient deficiencies, making them less effective for general nutrient supplementation where a more holistic approach is needed.

This understanding is crucial for arborists to properly assess and treat trees, recognizing when trunk implants and microinjections are appropriate and when alternative methods should be employed.