Which of the following would be the best example of conservation tillage?

Leaving crop residue on the surface is a prime example of conservation tillage. This practice retains the remnants of previous crops on the field after harvest, which serves multiple ecological purposes. It protects the soil from erosion by wind and water, maintains moisture levels, and fosters biodiversity by providing habitat for various organisms. Additionally, this residue breaks down over time, contributing organic matter to the soil, which enhances its structure, nutrient content, and overall health.

In contrast, plowing the land before planting disrupts the soil structure and can lead to increased erosion and loss of organic matter. Burning crop stubble removes useful nutrients from the soil and can lead to immediate soil degradation. Planting on sloped areas does not inherently relate to conservation tillage practices; instead, it may require specific methods to prevent erosion, but does not pertain to how the soil is managed in the context of conservation tillage itself. Thus, leaving crop residue is the most effective practice to promote soil conservation and health.