Which of the following factors is most likely to decrease germination percentage?

Dry soil is indeed a critical factor that can significantly decrease germination percentage. Germination requires a certain level of moisture for seeds to absorb water, which initiates the metabolic processes necessary for them to sprout. When the soil is dry, seeds are unable to take up the water they need, which inhibits germination.

Additionally, seeds need a supportive environment, including proper moisture levels, temperature, and sometimes specific oxygen availability. When moisture is lacking, seeds may remain dormant or die rather than germinating, leading to a lower percentage of successful sprouting.

In contrast, wet soil provides a conducive environment for germination, and still air conditions maintain humidity, both promoting seed sprouting rather than hindering it. High nitrogen fertilizer, while impacting seedling development, generally does not directly affect the germination percentage unless applied excessively to the point of seed damage, which is less common.