What would be a correct application of GDD in gardening?

The correct application of Growing Degree Days (GDD) in gardening is primarily related to tracking plant growth stages. GDD is a heat accumulation metric used to predict plant and insect development based on temperature. It helps gardeners understand the timing of plant growth phases, such as germination, flowering, and fruiting, by accumulating temperature data above a certain base temperature over a specified period.

GDD allows gardeners to make informed decisions about planting times and pest management, ensuring that actions are taken at the optimal moment for plant growth and health. This makes it an invaluable tool for managing and synchronizing gardening activities with the natural growth cycles of plants.

The other options, while relevant to gardening, do not accurately represent the purpose of GDD:

• Measuring nutrient levels focuses on the chemical aspects of soil and plant health.

• Analyzing soil composition deals with the physical structure and nutrients present in the soil.

• Testing herbicides' effectiveness pertains to evaluating the performance of weed control products, which is distinct from heat accumulation and plant development timing.

Thus, tracking plant growth stages is the appropriate context where GDD is effectively applied.