Which condition would typically require a two-pass approach for defoliation?

A two-pass approach for defoliation is typically required when there is a dense canopy of foliage. This situation arises because a dense canopy can hinder the effective penetration of defoliation agents, leading to uneven defoliation and potentially leaving a significant portion of the crop unaffected in the first pass. The purpose of a two-pass system is to ensure thorough coverage and efficacy of the defoliant, allowing for better leaf drop and maximizing the crop's yield potential at harvest.

In contrast, a drought-stressed plant often exhibits fewer leaves, which may not necessitate a second application, as the stress diminishes the overall foliage that needs to be defoliated. The early flowering stage of cotton may also allow for a single application to be effective because the plant is actively developing, which can aid in the response to defoliation. Soil deficiency typically impacts growth and overall plant health but does not inherently require a two-pass approach for defoliation. Hence, the condition of a dense canopy is crucial in determining the need for such an approach.