What is the "half-life" in relation to herbicide concentration?

The definition of "half-life" specifically refers to the time it takes for the concentration of a substance, such as a herbicide, to decrease to half of its original amount. Understanding the half-life is crucial for herbicide management, as it affects how long the chemical remains active in the environment and influences the timing of subsequent applications. This measure also plays a significant role in evaluating the potential impact on non-target species and the persistence of chemicals in agricultural practices.

The other options do not accurately reflect the meaning of half-life. While expiration of a herbicide refers to its effectiveness, it does not define the concentration change over time. The effectiveness duration in soil and recovery time for plants after application involve different factors that are not captured by the concept of half-life.